Organic Waste Management for EBI in Quebec, Feedstock Analysis
by
Olivier Sylvestre
Bachelor's Degree in Civil Engineering
Universit6 de Sherbrooke, 2012
Submitted to the Department of Civil and Environmental Engineering Partial Fulfillment of the
Requirements for the Degree of
Master of Engineering in Civil and Environmental Engineering
at the
Massachusetts Institute of Technology
NSTTE
NSASUETTW
'
June 2014
3BRARIES
C2014 Olivier Sylvestre. All Rights Reserved.
The author hereby grants to MIT permission to reproduce and distribute publicly paper and electronic copies of this
thesis document in whole or in part in any medium now known or hereafter created.
Signature of Author:
Signature redacted
Department of Civil and EnvironA1al Engineering
May 9, 2014
Certified by:
Signature redacted
E. Eric Adams
Senior Lecturer and Senior Research Engineer of Civil and Environmental Engineering
Tbesis Supervisor
Accepted by:
Signature redacted
Heidi M. kNepf
Chair, Departmental Committee for Graduate Students
Organic Waste Management for EBI in Quebec, Feedstock Analysis
by
Olivier Sylvestre
Submitted to the Department of Civil and Environmental Engineering on May 9, 2014 in Partial
Fulfillment of the Requirements for the Degree of
Master of Engineering in Civil and Environmental Engineering
at the
Massachusetts Institute of Technology
ABSTRACT
EBI is a company located in the province of Quebec in Canada with the mission to integrate
waste management. Great challenges in regards to organic waste management are faced and
anaerobic digestion is considered by EBI as an innovative alternative to landfilling. The selection
of the feedstock is a key success factor for an anaerobic digestion project. Based on an extended
literature review, an investigation of organic waste available to EBI and a multi-criteria analysis,
it is recommended to use a mix of food waste, dewatered septic systems sludge, poultry manure,
wasted activated sludge, grease trap waste and liquid yeast as input for the anaerobic digester.
Thesis Supervisor: E. Eric Adams
Title: Senior Lecturer and Senior Research Engineer of Civil and Environmental Engineering
EXECUTIVE SUMMARY
The objective of this thesis is to recommend to the company EBI the optimal feedstock selection
for anaerobic digestion. Initially, the company wants to invest less than one million dollars in a
small-scale project which translates into an approximate capacity ranging between 1,000 and
2,000 tons per year. If it is successful, a large anaerobic digestion project may be envisioned as a
subsequent step for EBI.
Recommendations to EBI
Table 1: Parameters Calculated for the Small-Scale Optimal Mix (Mix 14)
Dry
Matter
(%)
(%)
Methane Production
(x10 3 m3
in CH 4 /MT)
C
ya)
CH4/year)
Fee
Quantity
(MT/year)
C/N
Ratio
(/N)
pH
1,000
200
18
7.5
10
29.4-47.8
29.4-47.8
60,000
14
6.9
38
127.6
25.5
3,000
100
100
74
5.5
19
53.7
5.4
10,000
9
7.0
5
15.0
1.5
5,100
50
10-39
5.0
15
Liquid Yeast
50
4
5.7
18
63.2-77.9
97.2-145.8
3.2-3.9
4.9-7.3
3,750
2,800
Total Mix 14
1,500
20-21
6.2
14
46.5-60.9
69.8-91.4
84,650
Mix
Food Waste
Dewatered Septic
Systems Sludge
Poultry Manure
Wasted Activated
Sludge
Grease Trap Waste
*
*
*
*
*
($/year)
Laboratory testing is strongly suggested in order to properly characterize each type of
feedstock evaluated. Also, laboratory scale anaerobic digestion may be used to reduce
uncertainties.
The organic waste needs to be inserted gradually during startup phase. Bacteria from
another anaerobic digester can also be seeded to accelerate the process. The full organic
loading rate of the digester is reached when bacterial activity is stable and methane
concentration in biogas is high enough which may take numerous weeks.
Close monitoring is required at all times and adjustments need to be performed with the
shortest reaction time possible to maximize efficiency.
Growing energy crops is currently not recommended due to EBI's desire to start
anaerobic digestion with limited investments, the high availability of organic waste,
technological and climatic limitations, and ethical concerns over land use.
From the quantities of food waste received in 2013 by EBI and the amounts potentially
available, it is possible to scale the optimal mix by a factor of about 12.5. Table 2
describes the quantities, characteristics, methane production and fees generated by the
probable large-scale mix.
5
Table 2: Parameters Calculated for the Large-Scale Optimal Mix (Mix 14)
Mix(Tar)
Food Waste
Poultry Manure
Wasted Activated
Sludge
Dewatered Septic
Systems Sludge
Grease Trap Waste
Liquid Yeast
Total Scaled Mix 14
*
Quantity
(MT/year)
C/N
Ratio
Dry
Matter
pH
(%)
Methane Production
(x103 m 3
3
(M CH/MT)
CH4/year)
Fee
($/year)
12,500
1,250
18
74
7.5
5.5
10
19
29.4-47.8
53.7
367.5-597.2
67.1
750,000
125,000
,200
9
7.0
5
15.0
18.0
61,200
1,100
14
7.0
38
127.6
140.4
16,500
500
10-39
5.0
15
63.2-77.9
31.6-39.0
37,500
100
4
5.7
18
97.2-145.8
9.7-14.6
5,600
16,650
21-22
6.2
12
38.1-52.6
634.3-876.2
995,800
When possible, long-term waste treatment agreements with clients are valuable to secure
delivery of organic waste and reduce risks related to feedstock availability.
Developing an expertise in anaerobic digestion may represent an interesting regional first mover
advantage for the company. Also, as a responsible corporate citizen of the world, EBI has the
duty to contribute to the efforts against climate change and anaerobic digestion appears to be an
innovative organic waste management alternative to landfilling.
6
ACKNOWLEDGEMENTS
The support of many people was necessary to make this project possible. Special thanks are
addressed to Pierre Sylvestre, Gilles Denis, Luc Turcotte, Maxim Sylvestre, Yvon Lafortune,
Yves Rousseau, Eric Girard, Mario Brunelle and Alain Brunelle from EBI for their tremendous
collaboration.
Chapter 1 of this thesis is coauthored with Alexandre Bouaziz and Jaclyn Wilson. Their theses
cover related subjects which are the design of the anaerobic digester and life cycle assessments
of organic waste management methods respectively.
Dr. Eric Adams is a very helpful advisor whose assistance was highly appreciated throughout the
project. Susan from the MIT Writing and Communication Center also deserves gratitude for her
exceptional contribution. Finally, thanks to Alexandre, Jaclyn, family members, friends,
classmates and everyone else who supported the realization of this thesis.
PROFESSIONAL RESPONSIBILITY
All the advice from professors, advisors, other experts and client's representatives are given for
academic purposes and do not involve their professional responsibility.
7
TABLE OF CONTENTS
Abstract...........................................................................................................................................
3
Executive Sum m ary ........................................................................................................................
5
A cknow ledgem ents.........................................................................................................................
7
Professional Responsibility .......................................................................................................
7
List of Equations...........................................................................................................................
10
List of Figures ...............................................................................................................................
10
List of Tables ................................................................................................................................
11
Abbreviations................................................................................................................................
13
Chapter: 1
15
EBI and Organic Waste M anagem ent Options....................................................
1.1
Introduction....................................................................................................................
15
1.2
Inform ation on EBI .....................................................................................................
16
1.3
Quebec's Specific Context..........................................................................................
18
1.3.1
Environm ental Characteristics.............................................................................
18
1.3.2
Econom ic Characteristics ...................................................................................
18
1.3.3
Social Characteristics...........................................................................................
19
Organic W aste M anagem ent Options ........................................................................
19
1.4
1.4.1
Landfilling ..............................................................................................................
19
1.4.2
A erobic D igestion (Com posting) ........................................................................
21
1.4.3
A naerobic D igestion ............................................................................................
25
1.5
Comparison of the Methods ........................................................................................
30
1.6
A nalysis..........................................................................................................................
31
1.6.1
U ncertainties ........................................................................................................
31
1.6.2
Barriers to Success...............................................................................................
33
Recom m endations ..........................................................................................................
34
1.7
Chapter: 2
Feedstock Analysis ...............................................................................................
36
2.1
Introduction....................................................................................................................
36
2.2
Objectives of EBI on Feedstock Selection..................................................................
36
2.3
Literature Review ...........................................................................................................
37
2.3.1
Characteristics of Feedstock ...............................................................................
37
2.3.2
Origins of Feedstock.............................................................................................
40
2.3.3
Bacterial N eeds...................................................................................................
43
2.3.4
Feedstock Used in Anaerobic Digesters Worldwide ..........................................
46
8
2.4
Investigation...................................................................................................................
48
2.4.1
Procedure ................................................................................................................
48
2.4.2
Organic Waste Currently M anaged by EBI........................................................
48
2.4.3
Potential Feedstock ...............................................................................................
53
2.4.4
Com position of Organic W aste...........................................................................
55
2.5
Potential M ixes ..............................................................................................................
60
2.5.1
Total Capacity.........................................................................................................
60
2.5.2
Calculation of Param eters....................................................................................
61
2.5.3
Form ation of the M ixes.........................................................................................
63
2.5.4
D escriptions of M ixes..........................................................................................
64
M ulti-Criteria A nalysis (M CA )..................................................................................
67
2.6.1
Before Treatm ent .................................................................................................
68
2.6.2
During Treatm ent..................................................................................................
76
2.6.3
Cumulative A nalysis.............................................................................................
84
Risk M anagem ent Analysis ........................................................................................
89
2.6
2.7
2.7.1
Strategic Issues ...................................................................................................
89
2.7.2
Stakeholders............................................................................................................
89
2.7.3
Tolerance Levels..................................................................................................
90
2.7.4
Sources of Risk and their Criticality....................................................................
92
Recom m endations......................................................................................................
98
2.8.1
O n the Current Project ........................................................................................
98
2.8.2
O n a G lobal Perspective .......................................................................................
101
2.8
Bibliography ...............................................................................................................................
105
A ppendix A : Characteristics of som e Biogas Feedstock............................................................
109
A ppendix B : Organic Waste M anaged by EBI in 2013..............................................................
111
A ppendix C : O ther Potential Organic W aste..............................................................................
Appendix D: Partial Chemical Composition of some Types of Organic Waste ........................
113
Appendix E: D etailed Description of the M ixes.........................................................................
115
Appendix F: Scores and V alues of the MCA .............................................................................
119
9
114
LIST OF EQUATIONS
Equation 1: Calculation of C/N Ratio of Multiple Substrates ...................................................
Equation 2: Calculation of Dry Matter Fraction of Multiple Substrates ...................................
Equation 3: Definition of the pH ..............................................................................................
Equation 4: Calculation of H+ Ions Concentration of Multiple Substrates...............................
Equation 5: Calculation of pH from H+ Ions Concentration of Multiple Substrates.................
Equation 6: Conversion of Methane Yield per Volatile Dry Matter to Methane Production
M ass ..............................................................................................................................................
Equation 7: Calculation of Methane Production per Mass of Multiple Substrates ...................
Equation 8: Calculation of Methane Production per Time of Multiple Substrates ...................
61
61
62
62
62
by
62
62
63
LIST OF FIGURES
Figure 1: Schematic Diagram of the Existing Infrastructure at EBI..........................................
17
Figure 2: Average Price of Electricity for Residential Customers in North American Cities
( /k Wh).........................................................................................................................................
19
Figure 3: Diagram of Compost Pile Ventilation...........................................................................
22
Figure 4: Schematic Diagram of the Projected Anaerobic Digester and the Existing Infrastructure
at E B I ............................................................................................................................................
34
Figure 5: Potential Sources of Biogas Production in Germany (Total Energy Potential of 417
P J/Y ear) ........................................................................................................................................
47
Figure 6: Feedstock Used in some Anaerobic Digesters in Japan.............................................
47
Figure 7: Pile of Food W aste .....................................................................................................
50
Figure 8: Pretreated Leaves Stored Before Being Composted .................................................
51
Figure 9: Effluents from Septic Systems Sludge Treatment Plant in 2012 ...............................
52
Figure 10: Initial Investment over Annual Capacity for Anaerobic Digestion Projects............ 60
Figure 11: Annual Quantities of Organic Waste in each Mix ...................................................
65
Figure 12: Total Value of the Mixes Based on the MCA..........................................................
88
10
LIST OF TABLES
Table 1: Parameters Calculated for the Small-Scale Optimal Mix (Mix 14) ..............................
5
Table 2: Parameters Calculated for the Large-Scale Optimal Mix (Mix 14) ..............................
6
Table 3: Food Waste Composting Facilities in the US.............................................................
25
Table 4: Anaerobic Digesters Processing Municipal Solid Waste in European Countries in 2006
28
......................................................................................................................................................
Table 5: Quantified Aspects of Composting and Anaerobic Digestion....................................
30
Table 6: Digestibility of Different Feedstock Compounds under Anaerobic Conditions ......
39
Table 7: Concentrations of Minerals Potentially Inhibiting Bacteria in Anaerobic Digestion..... 40
41
Table 8: Methane Yield of Common Energy Crops .................................................................
42
Table 9: Experimental Methane Yields of Algal Biomass ........................................................
Table 10: Description and Quantity of Microbial Groups in Anaerobic Digestion.................. 43
44
Table 11: Optimal Ratios of Organic Compounds in the Feedstock ........................................
45
..............................................................
of
Bacterial
Cells
Table 12: Theoretical Composition
Table 13: Minimum Recommended Quantities of the Main Nutrients in Anaerobic Digestion.. 46
49
Table 14: Quantities of Organic Waste Managed by EBI in 2013 ............................................
Table 15: Quantities of Organic Waste Unsorted or Managed by Other Companies................ 53
57
Table 16: Composition of Organic W aste (1 of 2) ...................................................................
58
Table 17: Composition of Organic W aste (2 of 2) ...................................................................
Table 18: Fee, Current Treatment, Current and Projected Transportation and Pretreatment Costs
59
of Organic W aste ..........................................................................................................................
66
Table 19: Param eters Calculated for the M ixes........................................................................
67
Table 20: Score Scale of the M CA ............................................................................................
67
Table 21: Abbreviations of the Types of Waste for the MCA..................................................
68
..............................................................
of
Fee
Criterion
on
the
Table 22: Score of the Mixes
Table 23: Score of the Mixes on the Criterion of Diversion of Waste Specific to Treatment ..... 70
Table 24: Score of the Mixes on the Criterion of Diversion of Waste Specific to Transportation
71
......................................................................................................................................................
Table 25: Average Score of the Mixes on the Criterion of Diversion of Waste........................ 72
73
Table 26: Score of the Mixes on the Criterion of Availability .................................................
74
Table 27: Score of the Mixes on the Criterion of Odor.............................................................
75
Table 28: Score of the Mixes on the Criterion of Purity ..........................................................
Table 29: Score of the Mixes on the Criterion of Suitability Specific to C/N Ratio................ 77
78
Table 30: Score of the Mixes on the Criterion of Suitability Specific to pH ............................
79
Table 31: Average Score of the Mixes on the Criterion of Suitability......................................
80
......................
Basis
on
a
Mass
of
Digestibility
Table 32: Score of the Mixes on the Criterion
Table 33: Score of the Mixes on the Criterion of Digestibility on a Time Basis ...................... 81
82
Table 34: Average Score of the Mixes on the Criterion of Digestibility..................................
83
Table 35: Score of the Mixes on the Criterion of Inhibitors......................................................
84
Table 36: Summary of the Criteria Before Treatment for the Mixes (1 of 2) ..........................
85
Table 37: Summary of the Criteria Before Treatment for the Mixes (2 of 2) ..........................
86
Table 38: Summary of the Criteria During Treatment for the Mixes........................................
87
Table 39: W eight of the Criteria Used in the M CA..................................................................
Table 40: Tolerance Levels of the Stakeholders Related to the Strategic Issues ...................... 90
93
Table 41: Criticality of the Sources of Risk on the Strategic Issues.........................................
11
Table 42: Composition of the Optimal Feedstock Mixes..........................................................
Table 43: Evaluation of the Scalability of the Types of Waste in Mix 14 .................................
Table 44: Parameters Calculated for the Scaled Mix 14 ............................................................
12
99
102
103
ABBREVIATIONS
$: Cent
$: Canadian Dollar
BOD: Biochemical Oxygen Demand
C/N Ratio: Carbon to Nitrogen Ratio
CAD: Canadian Dollar
COD: Chemical Oxygen Demand
CSTR: Completely Mixed Tank Reactor
DSSS: Dewatered Septic Systems Sludge
FPOW: Food Processing Organic Waste
FW: Food Waste
GTW: Grease Trap Waste
H+: Positively charged hydrogen
kg: Kilogram
km: Kilometer
kWh: Kilowatt Hour
L: Liter
MCA: Multi-Criteria Analysis
mg: Milligram
MT: Metric Ton (1,000 kg)
MW: Megawatt
N: Nitrogen
P: Phosphorus
PJ: Petajoule (1015 Joules)
PM: Poultry Manure
QTY: Quantity
RWFPI: Rinsing Water from Food Processing Industry
Ton: Metric Ton (1,000 kg)
US: United States
USD: US Dollar
VDM: Volatile Dry Matter
VS: Volatile Solids
WAS: Wasted Activated Sludge
13
14
Chapter: 1
1.1
EBI AND ORGANIC WASTE MANAGEMENT OPTIONS
INTRODUCTION
Covering almost 1.4 billion square kilometers,' Quebec is the largest province of Canada located
in the eastern part of the country. Its land area is the equivalent of about seventy times the size of
Massachusetts, 2 but the population is only over 8 million people.3 Quebec faces challenges
similar to those of the rest of North America in terms of consumption lifestyle resulting in high
production of waste per capita - 746 kilograms per capita and a total of 5.4 million tons of waste
needed to be eliminated from the entire province in 2011.4 The provincial government is aware
of the problem and has set up regulations to reduce the quantity of eliminated material.
One of the objectives of the regulations is relatively ambitious: landfill of putrescible organic
matter will be prohibited by 2020.5 However, as of 2012 only about 5% of the households have
access to organic waste collection and very few services exist for institutional, commercial and
industrial sectors.6 Two main solutions are envisioned to fulfill the future regulation: composting
and anaerobic digestion.
In Chapter 1, the company EBI is initially described with an evaluation of the environmental,
economic and social constraints specific to Quebec. Then, the three organic waste management
options competing in the province are covered which are landfilling, composting and anaerobic
digestion. The overview includes a description of the processes, the factors of influence, a
historic review and current facilities in operation. Based on the information provided, the organic
waste management methods are compared and analyzed. The chapter concludes with
recommendations on the optimal option. Chapter 2 emphasizes feedstock selection in anaerobic
digestion. First, EBI's objectives specific to this aspect are detailed. Next, an extensive literature
review is presented about the influence of the inputs on the treatment followed by an
investigation of the organic material available to EBI for anaerobic digestion. Subsequently,
Statistics Canada, 2012a
World Atlas, "Population, World Atlas, United States."
3 "Population by Year, by Province and Territory."
4 Recyc-Qu~bec, Bilan 2010-2011 de la gestion des matibres r6siduelles au Qu6bec, 14-15.
5 Direction des matieres r6siduelles et des lieux contamin6s, Service des matieres r6siduelles, Banissement des
matieres organiques de l'61imination au Qu6bec: 6tat des lieux et prospectives, VII.
6 Ibid., VIII-IX.
2
15
potential combinations of organic waste are compared and analyzed and a risk management
analysis related to feedstock is performed. Finally, recommendations are formulated with regards
to EBI's objectives.
Note that Chapter 1 of this thesis is coauthored with Alexandre Bouaziz and Jaclyn Wilson.
Their theses cover in greater detail the design of the anaerobic digester7 and life cycle
assessments of organic waste management methods8 respectively.
1.2
INFORMATION ON EBI
EBI is a family business founded in 1960 in Canada with the mission to integrate waste
management. The company collects and transports all the waste of municipal, institutional,
commercial and industrial sectors, sorts them and disposes of them in the best possible manner
using efficient and up to date infrastructure.
7 Bouaziz, "Design of an Anaerobic Digester in Quebec, Canada."
8
Wilson, "Life Cycle Analysis of Waste Management Options for EBI in Quebec."
16
Waste
iiiiiiiiiiililllll
IP Biogas Purification Plant - --
BioSas
LandfillOrgan
Leachatei
N t ra G s
Eldetiudity
Cogeneration Plant
Wastewater
f
rat
Treatment Plant
Solid Waste
Septic Systems Sludge
Liquid Waste
Treatment Plant
Se ptic
Systems
Composst
Sludge
Wast+e
Composting Platform
+ Limestone
MFertilizer
II
Figure 1: Schematic Diagram of the Existing Infrastructure at EBI
As illustrated in Figure 1, EBI's site contains many interconnected plants such as a landfill, a
wastewater treatment plant, a composting platform, a biogas purification plant and more.
Therefore, increasing capabilities to treat organic waste can enable the company to push
integration of waste management further. In order for such a project to be interesting for the
company, the investment and operating costs have to be as low as possible combined with the
highest potential revenues. Deeper analysis is necessary to take the optimal decision in this
complex scheme.9
9 Groupe EBI, 2010
17
1.3
QUEBEC'S SPECIFIC CONTEXT
The province of Quebec has several particularities needing consideration in the evaluation of the
management of organic waste. These elements are split in environmental, economic and social
aspects and explained below.
1.3.1
Environmental Characteristics
Quebec's territory is distinct; it is very large but most of the population lives in the South portion
of it, mostly along the Saint-Lawrence River. The largest city is Montreal which has the
territorial constraint of being located on an island. The entire metropolitan area counts over 3.5
million people.' 0
Quebec is a Northern region where the climate on most of the territory is cold, without dry
season and a warm to cold summer.' 1 Temperature may vary from 30 C during summer to -30 C
during winter. It is an important component to incorporate in the analysis of the management of
organic waste. Just like in a refrigerator, the bacteria responsible for the transformation of matter
stop working at cold temperatures. Heating has to be planned if a plant operating all year is
desired.
1.3.2
Economic Characteristics
The province has a unique economic landscape. In the 1960s, the provincial government decided
to develop hydroelectricity in the northern part of the territory where many rivers flow and few
people live. As a result, 96% of the electricity currently comes from hydropower which is a
renewable energy.
In addition, electricity produced in large hydropower plants has a
significantly low cost making Quebec the place where electricity is the cheapest in North
America.' 3 Moreover, electricity production, transmission and distribution are a monopoly
owned by Hydro-Quebec which has the government of Quebec as its only shareholder. Figure 2
illustrates a comparison of the price of electricity in various cities in North America.
10 Population by Aboriginal group, by census metropolitan area (2006 Census", Statistics Canada,
http://www.statcan.gc.ca/tables-tableaux/sum-som/101/cst01/demo64a-eng.htm, viewed on 10/20/2013.
" Peel, Finlayson, and McMahon, "Updated World Map of the K6ppen-Geiger Climate Classification," 1636-1639.
12 "Electricity Generation", Hydro-Qudbec, http://www.hydroquebec.com/about-hydro-quebec/ourenergy/hydropower/pdf/presentation-generation-comments-june-2013-en.pdf, viewed on 10/30/2013, p. 11.
13 Hydro-Quebec, "Electricity
Generation," 15.
18
Monthly billings for a typical consumption of 1,000 kWh (Rates in effect on Apnil 1,2012)
6.76
MONTREAL
WINNIPEG
7A6
8.17
SEATTLE
VANCOUVER
.78
12.90
EDMONTON
13.14
OTTAWA
13.57
TORONTO
15.01
HAUFAX
1GAS
BOSTON
22.26
SAN FRANCISCO
22.57
NEW YORK
0
S
15
10
20
25
Figure 2: Average Price of Electricity for Residential Customers in North American Cities
4
(0/kWh)
Social Characteristics
1.3.3
As shown by the political decisions of the Quebec government, the population is getting more
concerned about the environment. The province aspires to reduce its ecological impact on the
planet and the proper management of organic waste is one way to reach this goal.' 5 However, its
implementation has to be done with respect to people in order to make it successful.
1.4
ORGANIC WASTE MANAGEMENT OPTIONS
1.4.1
1.4.1.1
Landfilling
Process
Landfills can be used as the sole waste treatment option, or used in conjunction with other
options as discussed later. It is the method commonly used in Quebec for organic waste disposal.
Anaerobic processes, a result of the depletion of oxygen in pockets of the waste, are the primary
form of waste degradation in landfills.
Organic waste breaks down to release methane and
carbon dioxide, while inorganic waste breaks down more variably. For instance, sulfate produces
" "Electricity Generation", Hydro-Qu6bec, http://www.hydroquebec.com/about-hydro-quebec/our2
energy/hydropower/pdf/presentation-generation-comments-june- 013-en.pdf, viewed on 10/30/2013, p. 15.
Ministbre du D&veloppement durable, Environnement et Parcs du Qu6bec. Banissement des matieres organiques
de l'6limination au Qu6bec : 6tat des lieux et prospectives, 2012, Direction des matibres r6siduelles et des lieux
contamin6s, Service des matieres r6siduelles, p. VII.
15
16
Harrison, 1995, p. 51.
19
a metal sulfide, which can then produce hydrogen sulfide under acidic conditions, a hazardous
material. Liners, both natural and synthetic, are used in landfills to prevent the escape of
hazardous materials.' 7
Leachate and landfill gas are two byproducts of concern. Leachate is collected via these liners
and must be treated. Landfill gas, also known as biogas, is produced from the anaerobic
processes and must be controlled to avoid health and environmental risks.' 8 Biogas has to be
collected and burned or used for energy production.
1.4.1.2
Factors Influencing the Process
The major factor influencing waste degradation in a landfill is the type of waste that is deposited
in it. While the aerobic aspect is influenced by the amount of oxygen, the anaerobic processes are
responsible for most of the degradation. Generally, the factors influencing a landfill are similar to
those impacting anaerobic digestion, which is discussed in depth later.
1.4.1.3
Historic Review
Though disposal via landfill has been the primary waste management method since humans'
beginnings, formal landfills have come into play in the past two hundred years. " Until the 1970s,
the concept of "dilute and attenuate" was used, allowing the leachate to be diluted by
groundwater and attenuated as it travels down the layers of the landfill.20 Since this time, the
objective is to focus on containment, in which leachate is collected and treated.
Currently, landfills are designed to anticipate an eventual failure and implementing measures to
limit the risk of releasing leachate in the environment. Additionally, landfills are increasingly
designed to be with other types of waste management as well as being linked with energy
recovery.
1.4.1.4 Current Operations
Landfills are in operation worldwide, being the oldest and most common method of waste
management. The United States (US) alone has over 2,000 landfills in operation, with waste to
17 Harrison, 1995, p. 57.
Harrison, 1995, p. 60.
19 Harrison, 1995, p. 43.
18
20 Harrison, 1995,
p. 45.
2 Harrison, 1995, p. 48.
20
landfills consisting of over 50% of the waste generated, at least from 2008 and before. 22 EBI has
four main cells of landfills on its land. BFI Canada has been in operation in Quebec as well for
the past 25 years.
Their landfills operate with energy recovery, much like EBI. Many other
companies manage landfills all around Quebec.
1.4.2
1.4.2.1
Aerobic Digestion (Composting)
Biological Process
The process of composting is characterized by the degradation of organic matter by a consortium
of microorganisms with oxygen. Its main environmental advantage is to produce carbon dioxide
instead of methane, which contributes less to global warming. Feedstock may come from any of
the agricultural, residential, commercial, institutional or industrial sectors. According to Luc
Turcotte, General Manager of EBI Energie, maturation of the material takes up to six months.
After that period, a material rich in nutrients like phosphorus, nitrogen and potassium is
produced.2 4 It can be used in agriculture or gardening as a fertilizer. To ensure a proper content
of several components like nutrients, trace elements and pathogens, the compost produced has to
be analyzed.
During the process, heavily contaminated wastewater is produced which has to be collected and
treated before it is released in the environment. It may also be mixed with limestone to increase
the typical low pH of the wastewater to facilitate its use as a fertilizer in agriculture.
Considerable odor is also released when composting. Depending on the neighbors and the winds,
measures to control odor may be necessary.
1.4.2.2
Factors Influencing the Process
Aerobic digestion depends on numerous aspects, which mainly are the feedstock, temperature,
pH, aeration and moisture content. 26 Feedstock, also called substrate, is fundamental to the
digestion. Nutrient content and particle size dictate the process of aerobic digestion.27 A high
22
EPA, 2009
23
BFI Canada, n.d.
Direction des matieres residuelles et des lieux contamin6s, Lignes directrices pour 1'encadrement des activit6s de
compostage, 2.
25 Ibid., 3.
26 Diaz et al., Compost Science and Technology,
49-56.
24
27
Ibid., 49-50.
21
nutrient content with a high surface area fosters digestion by bacteria. Carbon, nitrogen,
phosphorus and potassium are the principal elements processed by microorganisms.28 In
addition, the ratio of organic carbon to nitrogen is important to calibrate because bacteria need
specific quantities of both.2 9
Composting produces high quantities of heat. Temperature can increase up to 90'C in certain
cases. Even if pathogens and viruses are mostly being eliminated at high temperature, very little
digestion occurs above 70*C. The optimal temperature range for composting is between 30*C
and 450C.O Some methods exist to monitor and control temperature in a composting process.
Heat extracted can even be used in other infrastructures.
The pH varies throughout digestion and is hard to control; nonetheless it remains an important
factor. It tends to acidify at the beginning of the process because acid is produced and pH
increases towards the end. The most efficient range is between 5.5 and 8.0, but in general
bacteria prefer a neutral pH. 3 1
Prmmsre
suctmn
finishe moripW~
-
0aaea
ftOdor
Peiforated
Porous
base
lifter plIe of
cm lco
os
9
Cordensale tap
Figure 3: Diagram of Compost Pile Ventilation32
As initially mentioned, aerobic digestion is characterized by the presence of oxygen. Therefore,
aeration needs to be provided to the system to prevent digestion from becoming anaerobic. Pile
28
Diaz et al., 2007, p. 50
29 Diaz et al., 2007, p. 51
30
Diaz et al., 2007, p. 53
3' Diaz et al., 2007, p. 54.
32 Clean Washington Center, "Will Composting Work for Us?
A Decision Guide for Managers of Businesses,
Institutions, Campuses, and Other Facilities."
22
turning is a direct but inefficient way to aerate; ventilation provides guaranteed results.3 3 A lot of
research and development is done on this aspect to optimize systems; 34 a diagram of two
different ventilation methods is illustrated on Figure 3. Ventilation can also provide temperature
and moisture control. A positive correlation between temperature and oxygen demand exists.3 5
Balancing moisture content is crucial to the process. Indeed, microorganisms stop degrading
organic matter under low humidity conditions. On the other hand, too high water content does
not allow air to penetrate the substrate. 36 During transformation, it is possible to monitor
moisture content and add water if needed. At the end of the degradation, humidity of the compost
has to be lower, approximately at 30%, to make sure it is biologically stable. 37
1.4.2.3
Historic Review of Composting
Prior to 1950, there was only a very basic understanding of the composting process, but no real
large-scale practical application existed. 38 According to Golueke, Sir Albert Howard developed
one of the first composting systems intended for hygiene purposes for sewage water in India in
th
39
the early 20th century.
During the 1950s and early 1960s, research investigated composting as a way to enhance the
quality of soils and a pilot scale experiment was made at University of California. Research
performed in Europe aimed more towards survival of pathogens and their potential impacts on
health. During that period, high hopes existed that composting would be an economically viable
waste management solution. However, poor implementation of the process brought results below
expectations.
40
A significant increase in research on composting occurred in the 1970s.41 The process was well
understood and further study was conducted on specific aspects. Still, its development was
33
Diaz et al., 2007, p. 55
34 Diaz et al., 2007, p. 54
36
37
Diaz et al., 2007, p. 55.
Diaz et al., 2007, p. 56
Diaz et al., 2007, p. 57
Bertoldi,
Golueke,
40 Golueke,
4' Bertoldi,
38
3
1996, p. 5
2009, p. 28
2009, p. 28
1996, p. 9
23
slowed by unfavorable economic returns. The 1980s saw three large-scale projects fail in the US
mostly due to wrong location and incorrect design, which resulted in odor problems.4 2
1.4.2.4
Current Operating Composting Infrastructure
Many composting infrastructures are in operation worldwide. The current section goes over
EBI's facility before presenting a broad overview of the food waste composting plants in the US.
Finally, specific facilities are described in Canada and the US.
EBI currently operates a platform used to transform organic matter into compost. 4 3 Most of the
inputs are leaves, grass, wood chips and several residues from food industries. Even though the
facility is located in a low density area, odor is monitored and appropriate guidelines are usually
met. However, the compost produced has a relatively poor quality due to the presence of nonorganic contaminants like plastic residues, which reduces its value. Another similar open-air
composting facility is operated by the city of Guelph in Ontario, Canada where odor emissions
became a problem.44 Due to complaints from neighbors, the plant had to stop receiving organic
waste for a period of time and an odor management plan had to be developed before the plant
was allowed to treat material again. 45
Table 3, retrieved from Levis et al. (2010), lists the food waste composting facilities in the
different regions of the US. It is observed that very few large-scale treatment units exist and most
food waste composting infrastructures use material originating from the industrial, commercial
and institutional sectors. 46
Bertoldi, 1996, p. 10
43 D6p6t Rive-Nord, n.d.
44 City of Guelph, n.d.
42
45
46
Ibid.
Levis et al., "Assessment of the State of Food Waste Treatment in the United States
and Canada," 1488.
24
Table 3: Food Waste Composting Facilities in the US47
Region
Total
Capacity
> 5,000
> 50,000
MT/year MT/year
Commercial
or Municipal
Composters
Residential
Waste
Accepted
New England
51
9
2
16
8
Northeast/Mid-Atlantic
48
6
3
15
3
Southeast
18
4
2
11
3
Upper Midwest
48
13
3
17
10
Mountain
36
6
5
27
13
West
72
19
9
45
34
273
57
24
131
71
Entire US
A covered plant is located in Brampton in Ontario, Canada. It appears to be successfully
operating with a 60,000 tons per year capacity. 48 Moving to a larger scale, Edmonton, Alberta
has a plant treating municipal organic waste along with sewage sludge with a capacity of
200,000 and 25,000 tons per year respectively. 4 9 Also with an annual capacity of over 200,000
tons, a privately owned composting plant is located in Wilmington, Delaware. The treatment is
partially indoor and covered during outdoor maturing.
1.4.3
1.4.3.1
Anaerobic Digestion
Biological Process
Anaerobic digestion is the degradation of organic matter by a consortium of bacteria in absence
of oxygen. Like composting, this process can be used to transform organic matter from virtually
any sector. The main difference from composting is that methane is produced during the
reaction, which has a good energy potential. This process is slow because the microorganisms
5
need a large amount of energy in the form of heat and nutrients to degrade organic matter. '
47
Ibid.
BioCycle, n.d.
City of Edmonton, n.d.
50 Environmental Protection, "Waste Management Adds Largest Composting Facility in the Eastern U.S. to Network
of Organics Processing Facilities."
5' Tchobanoglous, Burton, & Stensel, p. 571-572.
48
4
25
Degradation can be divided in four main steps: hydrolysis, acidogenesis, acetogenesis and
methanogenesis. 52 They are briefly explained below.
In simple terms, hydrolysis is the degradation of large molecules into smaller compounds,
hydrogen, and acetic acid. During the second step, the acidogenesis, the smaller molecules from
hydrolysis are transformed into volatile fatty acids, hydrogen, and acetic acid.53 Next, the
acetogenesis involves the complete transformation of volatile fatty acids into carbon dioxide,
hydrogen, and acetic acid. Finally, hydrogen and acetic acid are both converted into methane
during the methanogenesis.
1.4.3.2
Factors Influencing the Process
The quantity and quality of biogas produced depends on numerous factors including
concentration of microorganisms, type of feedstock, specific surface area of material, reactor
type and its operation, light, pH and temperature.55
Bacteria responsible for degrading organic matter have a time of generation ranging from under
twenty minutes to sixteen days.56 For this reason, feedstock has to stay long enough in the
digester to give time for microorganisms to be generated and degrade organic matter. A way to
increase concentration of bacteria is to recycle biomass in the reactor. The type of feedstock used
is fundamental to degradation. Microorganisms need various nutrients to pursue an efficient
transformation. Lack of an element can compromise the process. Some feedstock can produce
intermediate products like fatty acids that inhibit reaction.:
Also, the form of the input is
important to the rate of the reaction; a higher surface area facilitates degradation.58
Three main types of reactors exist and impact the process which are batch reactor, completely
mixed tank reactor (CSTR) or plug flow reactor. 59. They differ in the continuity of the system and
52
Cheng, 2010, p. 154
53 Cheng, 2010, p. 154
5
Cheng, 2010, p. 154
5
56
Deublein
Deublein
Deublein
Deublein
57
58
59
& Steinhauser, 2011, pp. 112-127
& Steinhauser, 2011, p. 113
& Steinhauser, 2011, p. 114
& Steinhauser, 2011, p. 115
"The biogas handbook", Edited by Arthur Wellinger et al., Woodhead Publishing Limited, United States, 2013,
p.
196.
26
its mixing which influences retention time. More details on reactor types is found in Alexandre
Bouaziz's thesis. 60
Light acts as an inhibiter for microorganisms doing the transformation so it has to be avoided. 61
Furthermore, the optimal pH range for the degradation of organic matter is between 6.5 and
8.2.62
Temperature determines the types of bacteria generated. The general principle is that higher
temperature has an increased transformation rate. Psychrophilic digestion is in the range of 1 00 C
to 25'C and is known as a cheap, but inefficient process. 63 Moderate temperatures of about 30'C
to 37 0 C characterize the mesophilic process. This type of system is an interesting balance
between rate of performance, initial investment, ease of implementation and stability. 64
Thermophilic digestion typically happens between 50'C and 65'C. The advantages of this
degradation are the high rate of reaction and the removal of most pathogens and viruses.
However, it is more sensitive to temperature variations, hard to start and requires high initial and
operational costs.
1.4.3.3
65
Historic Review of Anaerobic Digesters
The first anaerobic digester intended to produce energy was built in France in 1860. The first
digestion unit in the US was made in 1926. As the cheap price of fossil fuels limited interest in
the technology, North America and Europe did little work towards the development of anaerobic
digesters. Nonetheless, the oil-crisis in the US in the 1970s gave a second burst to research in
anaerobic digestion, but it only lasted during the crisis. 66
Today, interest in organic waste digestion has increased due to the high price of fossil fuels and
increasing environmental concerns. It is reported by Cheng that over 4,000 anaerobic digestion
60
61
Bouaziz, "Design of an Anaerobic Digester in Quebec, Canada."
Deublein & Steinhauser, 2011, p. 123
62 Speece, Anaerobic Biotechnology for Industrial Wastewaters, 58.
63
Cheng, 2010, p. 157
64
Cheng, 2010, p. 158
65
Cheng, 2010, p. 161
66
Cheng, 2010, pp. 152-153
27
plants were in operation in Europe in 2005 producing the equivalent of 2.3 million tons of
petroleum annually.6 7
1.4.3.4
Current Operating Anaerobic Digesters
Numerous plants are operational around the globe. This section initially presents the municipal
solid waste anaerobic digesters in Europe. Next, a few specific facilities in North America are
described.
Levis et al. draws some interesting some interesting conclusions regarding anaerobic digestion
facilities processing municipal solid waste in European countries in 2006 presented in Table 4.
Even if such a feedstock contains a significant fraction of non-digestible material, the high cost
of energy in Europe and political incentives make this process economically sustainable. 68
Table 4: A naerobic Digesters Processing Municipal Solid Waste in European Countries in 200669
Country
Germany
Spain
Switzerland
France
Netherlands
Belgium
Italy
Austria
Sweden
Portugal
United Kingdom
Denmark
Poland
Total
Number of Plants
55
23
13
6
5
5
5
4
3
3
2
2
1
127
Total Capacity (MT/year)
1,250,000
1,800,000
130,000
400,000
300,000
200,000
160,000
70,000
35,000
100,000
100,000
40,000
20,000
4,605,000
A facility with 35,000 tons per year capacity is located in Oakland, California reporting
operating costs of about 40 to 55 US dollars (USD) per ton.
70
Biogas is used to produce
electricity to fulfill the plant's needs and the surplus is sold to the local utilities. Water is
partially removed from the digestate which is either used as a fertilizer in agriculture or as a daily
67
Cheng,2010, p.153
68 Levis et al., "Assessment of the State of Food Waste Treatment in the United States and Canada," 1487.
69
Ibid.
70
ILSR, 2010, pp. 5-6.
28
cover in a local landfill. 7' The city of Toronto, Ontario owns two anaerobic digestion plants,
newly renovated in one case and newly constructed in the other.72 Their summed capacity is
110,000 tons annually and the city plans to expand to 180,000 tons per year.7 3 They treat
municipal organic waste collected through a large municipal initiative.74 Based on an analysis
from the city of Toronto, operational costs used to be 90 Canadian dollars (CAD) per ton but are
estimated to decrease to 69 CAD per ton with the new plants.75 Very recently, a large-scale
organic waste digester started to operate in London, Ontario. 76 It has an annual capacity of about
65,000 tons and an electricity production of approximately 2.8 MW. The project is economically
viable, but strict constraints have to be met. According to Alex MacFarlane from Harvest Power,
the company owning the digester, electricity has to be sold at over 0.13 CAD per kWh and the
company has to charge over 45 CAD per ton to collect the feedstock. The same company
operates a large composting facility in Richmond, British Columbia where the first commercial
high-solids anaerobic digester was installed in parallel to a composting facility. The anaerobic
digester can transform 30,000 tons per year.77 Indeed, a large range in the capacities of the
existing plants is observed. The factors influencing this crucial design parameter are discussed in
Section 1.6.1.
The province of Quebec generated over 4.4 million tons of organic waste in 2010 with a
valorized fraction estimated to 20%.78 The Government of Quebec recently granted subventions
to many cities for the construction of anaerobic digestion infrastructure; some of them are
combined with composting. The city of St-Hyacinthe currently has the only anaerobic digester
functioning in the province, but Rivibre-du-Loup, Quebec city, Rocher-Perc6, the Monteregie
region, La Prairie, Beauharnois-Salaberry, and Rousillon all have projects on the drawing table.79
Moreover, the city of Montreal currently plans to have two indoor composting facilities and two
71
72
ILSR, 2010, p. 5
City of Toronto, n.d.
73
ILSR, 2010, p. 7
74
City of Toronto, n.d.
ILSR, 2010, p. 8.
7
76
"Anaerobic Digest," 2013
Harvest Power, n.d.
Recyc-Qu6bec, Bilan 2010-2011 de la gestion des mati&es r6siduelles au Qudbec, 8.
79 Gouvernement du Qudbec, "Programme de traitement des matieres organiques par biom6thanisation et
compostage."
77
78
29
anaerobic digestion facilities located on its territory; three facilities are expected to be in
operation by 2016 and the forth one is supposed to open in 2020.0
1.5
COMPARISON OF THE METHODS
Once the organic waste treatments available to EBI are explained in light of the constraints that
apply to Quebec, they can be compared in order to select the optimal option.
Regarding landfilling, it is the cheapest and the most common option. However, the regulation
prohibiting this landfilling of putrescible organic waste by 2020 in Quebec indicates to EBI that
an alternative has to be sought. The two other realistic avenues are composting and anaerobic
digestion. Table 5 is a brief summary of the main aspects involved in these organic waste
treatments. Note that only indoor composting is considered.
Table 5: Quantified Aspects of Composting and Anaerobic Digestion
Aspects
Investment
Composting
450 CAD/MT"
Anaerobic Digestion
300-900 CAD/MT12
Maturation
Up to 6 months
15-60 days83
Operating cost
~% 80 CAD/MT8 4
45-70 CAD/MT 85
Low 86
High
Output value
It is important to note that the investment cost for composting solely comes from the facility in
Edmonton and might not be representative of all composting plants. In the case of anaerobic
digestion, a high variability is observed. In both methods, the investment needed is specific to
every project and a realistic range of values is hard to provide. It is influenced by all the design
factors explained previously.
80 Ville de Montreal, "Centres de traitement des matieres organiques."
81 Office of the City Auditor, Edmonton Composting Facility Review,
Edmonton, 2003, p. 1.
82 Institute for Local Self-Reliance, Update on Anaerobic Digester Projects Using Food Wastes in North
America,
United States, 2010, Division of Sustainability City of Atlanta, Georgia, p. 8.
83 KHANAL, Samir Kumar. Anaerobic biotechnology for bioenergy production: principles and applications, WileyBlackwell, 2008, United States, p. 95.
84 CM Consulting, Measuring the benefits of composting
source separated organics in the region of Niagara,
Canada, 2007, The Region of Niagara, p. 2.
85 Institute for Local Self-Reliance, Update on Anaerobic Digester Projects Using Food Wastes in North America,
United States, 2010, Division of Sustainability City of Atlanta, Georgia, p. 8.
86 Office of the City Auditor, Edmonton Composting Facility
Review, Edmonton, 2003, 10-11.
30
There is a clear gap between maturation times for the two treatments. Anaerobic digestion is
much faster. A composting plant needs a lot of storage to allow the material to mature during
several months, which is costly. More details can be found on this aspect in Jaclyn Wilson's
thesis.
Again, operating costs are highly variable because they are specific to each project. The two
methods are in the same order of magnitude and a clear difference cannot be established.
The output value favors anaerobic digestion because of the methane production. Both methods
produce fertilizer and heat which are valuable, but have limited applications. However, the
methane produced by anaerobic digestion represents a remarkable asset with a wide range of
possible uses.
From the information summarized, there is no clear monetary advantage for either treatment
process. However, maturation time and the value of the outputs of anaerobic digestion are
superior to those of composting.
1.6
ANALYSIS
The current analysis critiques the information previously covered by raising uncertainties
observed and evaluating the barriers to success in the two methods.
1.6.1
Uncertainties
The two different ways to treat organic matter rely on biological degradation done by different
consortia of bacteria. They present numerous uncertainties which may substantially alter the
economic viability of projects. In the two cases, feedstock has a major influence on the outputs.
Although industrial food waste may be relatively constant over the course of a year, residential
organic waste significantly changes from season to season which impacts the performance of the
process. The quality of residential source-separated organic waste depends on the good will of
people to sort properly their organic matter which is virtually impossible. Plastic bags or other
non-organic contaminants are always found. Potential pretreatments are described in Chapter 2.
Furthermore, anaerobic digestion's viability relies on the market price of energy from other
sources which is barely predictable but has a direct impact on revenues. Competing against
31
natural gas is not simple because prices in North America are extremely low due to the extraction
of shale gas in the US. If this trend continues, it can possibly reduce the interest in methane.
On the economic side, the comparison presented before reflects the great range of investment
and operating costs which cannot be used to determine if a method is preferable. The economics
are specific to each project and are barely comparable. For this reason, no monetary advantage is
considered for any treatment.
Another uncertainty is the political position which can imply influential decisions. The
renewable aspect of the two methods is definitely a great asset, but if it is too costly, odor is
emitted or trucking causes problems, strict measures may be enforced.
On a plant size perspective, it is hard to determine if one large plant is preferable to many
smaller ones. The first option certainly presents economies of scale during construction and
operation, but the second alternative brings flexibility. Instead of building a large treatment unit
that will be used at full capacity after a long period, building smaller plants over time has the
capability to adapt to demand. Economies of scale have to be balanced against flexibility to
identify which option is superior for a given project. On the biological side, it appears that
digestion at large scale presents greater uncertainties related to the imperfections of the
treatment. It is more complex to obtain a complete homogeneity of the substrate during the entire
process.
From a technical point of view, it is hard to compare quantities of wastewater and heat produced
by the two studied treatments. The amount of leachate depends on the difference of water content
in the substrate between the beginning and the end of the treatment plus any water added to
facilitate degradation. It may be assumed that open-air composting plants involve more
wastewater treatment because of storm water. However, it is unclear whether more leachate is
produced in a covered composting plant or in an anaerobic digestion. The same difficulty applies
to production of heat. These two factors may be highly variable and specific to each project.
32
1.6.2
Barriers to Success
Currently in Quebec, the main barriers to success to treat organic matter are the lack of
infrastructure to collect it and to treat it. In order to achieve the ambitious goal of not landfilling
organic waste by 2020, the government has to greatly incentivize cities and private companies to
collaborate in the management of organic waste.
The high competition the outputs face is an additional challenge. The fertilizer produced is on the
same market as chemical fertilizers which are more expensive but more efficient. In the case of
biogas, it competes against fossil fuels which are cheap and abundant sources of energy.
Finally, Quebec has cheap and renewable electricity available, but, the monopoly situation in the
electricity sector can be an obstacle by blocking competition. The fact that companies are only
allowed to sell electricity to Hydro-Quebec limits the economic potential of electricity
production from biogas.
33
1.7
RECOMMENDATIONS
It is recommended that EBI favors anaerobic digestion over composting under certain conditions
explained below.
saste
SC
r Gs
fiogas Purification Pmn
Wl B..
Heat
Leachate
Wastewater
Treatment Plant
Solid Waste
Biogas
Waste
Liquid
Septic Systems Sludge
C +Lnestionen
obitDgete andnEtExitin
oenoetener
Digam
Figurei4: Sceai
(pndected
Digestate
Treatment Plant
Septic
Systems
Sludge
COprg
Cmo
nrstutr
C
r
2.
astc
"at
Organic
W/aste
Composting Platform _
+ Limestone
I,,Friie
Figure 4: Schematic Diagram of the Projected Anaerobic Digester and the Existing Infrastructure
at EBI
Given all the different facilities already owned by the company, constructing an anaerobic
digester can enable the company to push integration of waste management further as displayed in
Figure 4. To ensure the viability of an anaerobic digester, the company needs a strong market
evaluation of feedstock availability with great quality and quantity in the area of the plant.
Moreover, the initial capital expenses have to be within EBI's capabilities.
Some non-organic contaminants in the substrate can have a considerable impact on methane
production which may involve pretreatment. This specific concern is addressed in Chapter 2.
34
Unless a lucrative contract with Hydro-Quebec to produce electricity is possible, biogas, purified
into natural gas or not, may preferably be used as a fuel for vehicles because it competes against
gasoline and diesel instead of natural gas. As mentioned previously, the price of natural gas
dropped in the past years, but gasoline and diesel remain relatively expensive. Still, this option
presents the challenge of setting up infrastructure to fuel vehicles and fostering the conversion of
vehicles to natural gas. In the case of corporate customers, it is possible to reach a sufficient
number of vehicles quite rapidly, but the operation becomes significantly complex if targeted to
the public. The use of biogas has to be properly planned in order to gain the maximum benefits
out of it.
Anaerobic digestion is favored over composting mostly because of the methane production. This
project can help the company to increase the amount of biogas to its biogas purification plant
which may represent an interesting source of revenue for the company. Even if the system is
initially harder to set up, it brings a competitive advantage to EBI in a society with growing
energy needs.
35
Chapter: 2
2.1
FEEDSTOCK ANALYSIS
INTRODUCTION
An athlete is unable to perform to his full potential without the proper diet. Similarly, the
microorganisms found in anaerobic digestion have to receive the best nutrition to give their
optimal yield. The current chapter aims to determine the best combination of organic waste to
serve as input for the organic waste digester. A wide range of potential substrates exist which is a
key success factor for the project.
Initially, the objectives of EBI regarding feedstock are covered. In this Chapter, background
information includes technical aspects, bacterial needs and biomass types used worldwide in
anaerobic digestion. Next, Section 2.4 describes an investigation of organic material currently
received by EBI and potential additional quantities. Then, feedstock combinations are compared
and analyzed with a Multi-Criteria Analysis (MCA). A risk management analysis specifically on
feedstock follows. Finally, recommendations addressed to EBI can be found related to both
short-term and long-term perspectives.
2.2
OBJECTIVES OF EBI ON FEEDSTOCK SELECTION
As mentioned in Chapter 1, EBI has been in the waste management industry for numerous
decades. An objective of the company is to have the capability to treat organic matter while
efficiently using its existing infrastructure. As anaerobic digestion is a practice with substantial
uncertainties when performed at large scale, EBI remains careful about this avenue and desires to
invest a maximum of one million dollars for all the additional infrastructure required. By
building a smaller treatment unit, it is possible for the company to obtain practical experience
and test the concept before deciding to enlarge capacity. It is a way for EBI to take limited risks
while attempting to stay innovative in waste management.
Certainly, the feedstock selection has to comply with several constraints. In terms of operations,
the supply of the chosen organic matter has to be reliable and constant through the course of a
year to justify the investment and ensure stable digestion. Additionally, the nutritional needs of
the consortium of bacteria have to be readily fulfilled to result in an optimal methane yield and a
36
fast digestion. Regarding the economical aspect specific to feedstock, a high methane yield
brings greater income. Also, a fee is charged to clients to collect and treat their waste which
needs to be included in the project income. Expenses come from transportation, storage and
pretreatment requirements. The aspect of the environmental footprint of the feedstock is
important. It may have a positive impact if diversion from landfilling to anaerobic digestion is
accomplished or if a certain waste is transported a reduced distance. Furthermore, minimizing
odor emissions is the main social objective for EBI. Failure to address this concern can decrease
the acceptability of the project in the surrounding community. These factors frame the analysis
and recommendations on the optimal feedstock for the anaerobic digester.
Moreover, some assets on site may be used to grow energy crops for additional anaerobic
digestion. Phosphorus and nitrate are found at the septic systems sludge treatment plant; carbon
dioxide and heat are released from the cogeneration plant; water flows out of the wastewater
treatment plant. All these elements can possibly be used to grow crops for anaerobic digestion.
EBI is interested to explore this innovation. However, it represents additional expenses and
growing biomass aimed to anaerobic digestion tends to increase the environmental footprint of
the project; such elements are considered in the analysis.
2.3
LITERATURE REVIEW
The literature review specific to feedstock goes over the characteristics and origins of organic
material, the bacterial needs and the inputs used in anaerobic digesters currently operating
around the world.
2.3.1
Characteristics of Feedstock
Feedstocks can be defined based on their intrinsic and extrinsic characteristics. The most
important are suitability, availability, digestibility, impurities and inhibitors. Each one is
described in greater detail in the following paragraphs.
Suitability includes numerous internal characteristics related to a given feedstock that define the
anaerobic digestion potential. The pH, carbon to nitrogen (C/N) ratio, dry matter content and
particle size are the main ones.87 Appendix A presents a large number of feedstock with their
87
Wellinger, Murphy, & Baxter, 2013, p. 34
37
approximated suitability. Optimal conditions are found when pH ranges from 6.5 to 8.2, but it
may still be acceptable at 6.0. Yet, this criterion depends on alkalinity and volatile fatty acid
production. Speece reports that it is not recommended to neutralize sludge prior to digestion;
problems like high alkalinity during treatment may be caused leading to an excessively basic
pH.
Commonly, the ideal C/N ratio may range between 20/1 and 30/1. Still, it can be viable at a
lower ratio of 15/1 .89 Regarding the dry matter content, the digestion is considered wet when the
fraction is at 10% to 15% where the substrate mostly has the behavior of a liquid. Dry digestion
processes have dry matter content between 20% and 40%; the organic waste is not really dry
despite the nomenclature but more like a thick sludge with relatively low water content. 90
Moreover, feedstock below 15% dry matter can usually be pumped, facilitating operations. 9 1
Smaller particle size enhances digestion by increasing surface area and allowing more contact
between bacteria and substrate; optimal size is under 40 mm.92
Availability is defined as the accessibility of the feedstock for a specific anaerobic digestion
plant. It depends on the quantity at the source and transportation needed to bring it on site. Also,
some feedstocks have a seasonal variation, which needs to be considered.
The behavior of feedstock in anaerobic digestion is known as digestibility. 93 It is a core criterion
for methane production and retention time. The composition of the feedstock directly influences
digestibility and Table 6 summarizes the digestion time of different compounds. Lipids have the
highest methane yield, but a relatively long digestion time. Proteins degrade faster, yet present a
smaller methane yield.94 Note that combining feedstock, called codigestion, may produce a
global methane production greater than the simple addition of the single inputs explained by
"synergistic activity." 95 Moreover, digestibility of a substrate can be enhanced by pretreatment.
A wide range of techniques exists based on physical, biological or chemical processes.96 For
88 Speece, Anaerobic Biotechnology for Industrial Wastewaters, 58.
89 Puyuelo et al., "Determining C/N Ratios for Typical Organic Wastes Using Biodegradable Fractions," 653.
90 La M~thanisation - Rend Moletta, 93.
91 Steven Thomas Sell, "A Scale-up Procedure for Substrate Co-Digestion in Anaerobic Digesters through the Use
of Substrate Characterization, BMPs, ATAs, and Sub Pilot-Scale Digesters," 21.
92 La M6thanisation - Rend
Moletta, 93.
9 Wellinger, Murphy, & Baxter, 2013, p. 34
94 Weiland, 2010, p. 852
95 Long et al., "Anaerobic Co-Digestion of Fat, Oil, and Grease (FOG)," 239.
96 Wellinger, Murphy, and Baxter, The
Biogas Handbook, 2013, 4.
38
economic purposes, feedstock is typically selected with a high methane yield and low retention
time.
Table 6: Digestibility of Different Feedstock Compounds under Anaerobic Conditions"7
Compound
Digestion Time
Low molecular weight carbohydrates, volatile fatty acids, alcohols
Proteins, hemicellulose, lipids
Cellulose
Hours
Days
Weeks
Purity of feedstock is determined as the quantity of undesired material entering the anaerobic
digester. Impurities can disturb the process by causing sedimentation, foaming, floating layers or
damage to equipment. Granular material, straw, wood, glass and metal are the typical unwanted
elements. They are either not digestible or very slowly digestible and need to be avoided in
anaerobic digestion. Additional impurities can be pathogens or other microorganisms, in which
case the feedstock is required to be pasteurized or sterilized before being digested.98
An inhibitor is a compound with a negative effect on bacterial activity, with the potential to
break the balance of the digester or stop the biological activity. 99 Inhibition depends, among
other things, on concentration and feedstock type.1 00 Table 7 lists concentrations of major
compounds that may inhibit bacteria responsible for the treatment. The effect is however highly
variable and barely predictable partly because microorganisms have the capability to adapt to
certain adverse environmental conditions.'01 These elements need to be monitored closely and
avoided in order to have constant anaerobic digestion.
97
Wellinger, Murphy, & Baxter, 2013, p. 35
98 Weiland, 2010, p. 852
Wellinger, Murphy, & Baxter, 2013, p. 35
10 Deublein & Steinhauser, 2011, p. 130
101 Deublein & Steinhauser, 2011, pp. 130-131
99
39
Table 7: Concentrations of Minerals Potentially Inhibiting Bacteria in Anaerobic DigestionO2
Compound
Moderate Inhibition
Ammonia
Calcium
Chromium (III)
Chromium (VI)
Copper
Magnesium
Nickel
Potassium
Sodium
Sulfur
Zinc
2.3.2
(mg/L)
1,500-3,000
High Inhibition (mg/L)
3,000
8,000
180-420 (total)
3.0 (soluble), 200-600 (total)
0.5 (soluble), 50-70 (total)
3,000
2.0 (soluble), 30 (total)
12,000
8,000
200
1.0 (soluble)
2,500-4,500
1,000-1,500
2,500-4,500
3,500-5,500
200
Origins of Feedstock
Another useful categorization of feedstock is by its provenance being agricultural, industrial,
commercial or municipal. 0 3 Each sector is explored from a broad perspective in the current
section.
Agriculture is known to provide the most important biogas generation potential and is composed
of manure, residues, by-products or, most recently, energy crops.104 Important quantities of
manure are produced by livestock and it represents a suitable feedstock for anaerobic
digestion. 5 Nonetheless, solid manure has a low methane yield and impurities like straw are
usually found so it is preferable to combine it with other feedstock in order to have an
economically viable operation. Residues and by-products commonly present low digestibility
with high content of cellulose requiring pretreatment and digestion with other organic
material.10 6 Energy crops are plants grown specifically for anaerobic digestion. Currently, they
are crops without wood because the lignin it contains is not suitable in anaerobic digestion. The
Moletta, Le traitement des d6chets, 477.
Wellinger, Murphy, & Baxter, 2013, p. 20
104 Wellinger, Murphy, & Baxter,
2013, p. 22
15 Wellinger, Murphy, & Baxter,
2013, p. 23
106 Wellinger, Murphy, &
Baxter, 2013, p. 24
102
03
40
main types of energy crops are maize, grassy plants, cereals and vegetables.107 A range of
methane yields is shown in Table 8.
Table 8: Methane Yield of Common Energy Crops'08
Energy Crop
Methane Yield
(i 3 CH 4/MT VS)
Fodder beet
Leaves
Ryegrass
Hemp
Barley
Alfalfa
Triticale
Grass
Clover grass
Potatoes
Straw
Oilseed rape
Sugar beet
Maize (whole crop)
Sunflower
Nettle
420-500
417-453
390-410
355-409
353-658
340-500
337-555
298-467
290-390
275-400
242-324
240-340
236-381
205-450
154-400
120-420
Marine feedstock can also be included in energy crops. It is a fairly new domain with high
potential where most of the activities are at the research level.10 9 Algae grows faster, which
brings a greater land use efficiency compared to conventional crops." 0 Macroalgae and
microalgae are the two different types of marine crops."' Hamani Abdou, in an academic project
partly funded by EBI in 2012, found the results summarized in Table 9. When compared to the
methane yields listed in Appendix A, macroalgae's methane yield is an order of magnitude
below most of the values. Regarding microalgae, methane yield is comparable to most of the
other types of feedstock. Additionally, some algae may be pretreated to enhance methane
107
108
09
110
"
Wellinger, Murphy, & Baxter, 2013, p. 25
Wellinger, Murphy, & Baxter, 2013, p. 25
Wellinger, Murphy, & Baxter, 2013, p. 32
Wiley, Campbell, & McKuin, -2011, p. 326
33
Wellinger, Murphy, & Baxter, 2013, p.
41
production by increasing dry matter fraction, reducing particle dimensionn2 or diminishing
inhibitory salt concentrations in the case of seawater biomass."
3
On the negative side, growing
energy crops involves additional costs and reduces environmental benefits due to the use of
fertilizers and energy to harvest.' 1 4
Table 9: Experimental Methane Yields of Algal Biomass' 15
Methane
Yield
3
C /M
V)
Type of Algae(i
(M CH4/MT VS)
44-70
Macroalgae
Freshwater Microalgae
258-430
Seawater Microalgae
235-419
The industrial sector produces a wide variety of by-products in terms of suitability and
digestibility. These residues come from food, pharmaceuticals, biochemical cosmetics and pulp
and paper industries. Usually, they are characterized by a high purity and a low variability. Some
industrial feedstock with a significant biogas yield can be used as boosters for anaerobic
digestion. 116
Feedstock coming from the commercial and municipal sectors is either organic waste or sewage
sludge.
Organic waste is collected from shops and households, ideally sorted at the source to
reduce as much as possible the quantity of impurities."
8
It must be over 99.9% pure in order to
avoid disturbance of the process.'" 9 However, source-sorted organic waste is usually composed
of approximately 10% contaminants.
20
Typically, the material originating from the commercial
sector contains a reduced fraction of contaminants, but pretreatment is required in either case. If
well sorted, this type of feedstock presents great environmental benefits by diverting waste from
12 Hamani Abdou, "Anaerobic Digestibility of Microalgae: Fate and Limitations of Long Chain Fatty Acids in the
Biodegradation of Lipids," 17-18.
"3 Ibid., 42.
114 Wellinger, Murphy, & Baxter,
2013, p. 26
115 Hamani Abdou, "Anaerobic Digestibility of Microalgae: Fate and
Limitations of Long Chain Fatty Acids in the
Biodegradation of Lipids," 39-48.
116 Wellinger, Murphy, & Baxter, 2013,
p. 27
117 Wellinger, Murphy, & Baxter, 2013, pp. 30-32
118 Wellinger, Murphy, & Baxter,
2013, p. 30
119 Wellinger, Murphy, & Baxter, 2013, p. 31
12 Levis et al., "Assessment of the State of Food Waste Treatment in the United States and Canada," 1490.
42
landfills.12 ' Sewage sludge is a very common feedstock worldwide; nonetheless, some pollutants
found in it cause limitations for the use of the digestate as a fertilizer.122
2.3.3
Bacterial Needs
The nutritional needs of the bacteria are fundamental in the selection of the feedstock; satisfying
their them is required to have the optimal yield. First, the types of bacteria present in anaerobic
digestion are identified. Second, macronutrients and micronutrients are covered in greater details.
Some differences in the classification between the two categories exist in the literature, but the
objective is to understand the overall nutritional requirements. Additionally, as discussed
previously, the pH, temperature, inhibitors and purity are key factors. The pH has to be ideally
neutral, temperature is a design parameter and inhibitors have to be avoided. Further, the highest
purity is desired, otherwise pretreatment may be needed.
The bacteria responsible for the anaerobic digestion process can be divided into five groups.
Table 10 shows the microbial groups as well as their roles and relative quantities. The
concentrations come from an experiment on an activated sludge anaerobic digester and provide
an order of magnitude of relative concentrations.
Table 10: Description and Quantity of Microbial Groups in Anaerobic Digestion 12 3
Role
Hydrolytic bacteria
Degrade polymers to
monomers
Ferment monomers to organic
acids and alcohols
Produce acetate from other
organic acids and alcohols
Produce methane from acetate
4
x
10"
7
x
108
Produce methane from
hydrogen and carbon dioxide
1
Acidogenic bacteria
Acetogenic bacteria
Acetotrophic
methanogens
Hydrogenotrophic
methanogens
121
122
1
Cell
Concentration
(per mL)
Microbial Group
Wellinger, Murphy, & Baxter, 2013, p. 30
Wellinger, Murphy, & Baxter, 2013, p. 32
Wang, Environmental Biotechnology, 31-32.
43
2 x 10"
5 x 108
x
108
Gerardi mentions the two main macronutrients: nitrogen (N) and phosphorus (P). They have to
be present and available in sufficient quantities to avoid limiting growth.124 In addition to these
two elements, Wang et al. lists carbon, hydrogen, oxygen, potassium, sodium, magnesium and
calcium. 125 According to Gerardi, it is possible to measure the amount of macronutrients in the
feedstock entering the anaerobic digester or the residual amount of macronutrients in the
digestate to target the adequate quantities required. Contrarily to the usual practice in
environmental engineering, the chemical oxygen demand (COD) is used instead of the
biochemical oxygen demand (BOD) to determine the quantity of organic compounds in the
feedstock. As explained by Gerardi, BOD tends to underestimate the value because the test is
done in aerobic conditions which are not representative of the environment in an anaerobic
digester.126 COD should preferably be above 2,000 mg/L. 2 7 Table 11 summarizes optimal ratios
of macronutrients for the feedstock. These numbers are empirical estimates and serve as a useful
tool to choose the feedstock.
Table 11: Optimal Ratios of Organic Compounds in the Feedstock
Organic Compound
Ratio
COD/N/P
350-1000/7/1
128
C/N129
20-30/1
The ratios originate from the empirical formula of cellular material which is C2H70 2N. Table 12
lists the main organic compounds forming bacteria and their respective fraction. This record is
another way to verify if the substrate is suitable for optimal anaerobic digestion.' 3 0
Gerardi, The Microbiology of Anaerobic Digesters, 93.
Wang, Environmental Biotechnology, 39.
126 Gerardi, The Microbiology of Anaerobic Digesters, 93-94.
127 Wang, Environmental Biotechnology, 409.
128 Gerardi, The Microbiology of Anaerobic Digesters, 94.
129 Wellinger, Murphy, and Baxter, The Biogas
Handbook, 2013, 34.
130 Gerardi, The Microbiology of Anaerobic
Digesters, 94-95.
124
125
44
Table 12: Theoretical Composition of Bacterial Cells131
Element
Approximate Percent Composition
(% Dry Weight)
Carbon
Oxygen
Nitrogen
Hydrogen
Phosphorus
Sulfur
Potassium
Others
50
20
12
8
2
1
1
6
If the second method is used which is to measure residual quantities of nutrients, Gerardi
recommends 5 mg/L of NH 4+-N and 1 to 2 mg/L of NP0 4 --P. If these values are respected, it
means that nutrients are present in good quantities in the digester and do not limit.132 In the case
that a growth constraint is observed due to a lack of nitrogen or phosphorus, ammonium
chloride, aqueous ammonia and urea can be added for the first element; phosphate salts and
phosphoric acid have the potential to counter phosphorus scarcity.133 However, such measures
have a cost and are not optimal from an economic perspective.
Even if micronutrients are only needed in lesser quantities, they remain essential in anaerobic
digestion. Gerardi highlights cobalt, iron, nickel and sulfur as the most important micronutrients
because they are required by the acetotrophic methanogens to produce methane from acetate.' 3 4
A more comprehensive but still incomplete list includes barium, copper, manganese,
molybdenum, nickel, selenium, tungsten, vanadium and zinc."5 These elements are commonly
present in several types feedstock, but a lack of micronutrients can threaten the operation of the
anaerobic digester. Thus, laboratory testing is necessary to certify that the right nutrients are
found. Gerardi states that the addition of 1.5 kg/M3 of yeast may provide the appropriate
micronutrients, as it is rich in amino acids, minerals and vitamins.'36
" Ibid., 95.
132 Ibid., 94.
133 Wang, Environmental Biotechnology, 410; Gerardi, The Microbiology of Anaerobic Digesters, 94-96.
134 Gerardi, The Microbiology of Anaerobic Digesters,
96.
"3 Ibid.; Wang, Environmental Biotechnology, 39.
136 Gerardi, The Microbiology of Anaerobic Digesters,
96.
45
Table 13 is a list of the most important nutrients and their minimum fraction of COD
recommended.
Table 13: Minimum Recommended Quantities of the Main Nutrients in Anaerobic Digestion
Nutrient
37
Minimum Fraction Recommended
(Mass Nutrient x 10-3/Mass COD Loading)
Cobalt
Iron
Nickel
Nitrogen
Phosphorus
Sulfur
0.1
2
0.01
30-40
5-10
2
The optimal feedstock may be determined by evaluating the requirements covered in the current
section. Good knowledge of bacterial needs is drawn and may enhance the feedstock selection.
2.3.4
Feedstock Used in Anaerobic Digesters Worldwide
Originally, animal manure as well as sewage sludge were the feedstocks used in anaerobic
digestion. Waste from industrial and municipal sectors became inputs in this process in the
1970s. In the 1990s certain European countries like Germany started to grow energy crops.' 38 As
of 2011, Deublin and Steinhauser report that 3% of the primary energy carriers originate from
biomass in developed countries while it is estimated to be 38% in emerging countries.' 3 9 These
numbers are not restricted to anaerobic digestion but express the variability of biomass
management across the globe. Some regions are studied below with a specific interest on the
origin of biomass.
137
Ibid.
138
Wellinger, Murphy, & Baxter, 2013, p. 20
139 Deublein & Steinhauser, 2011, p.
39
46
Energy crops___
59%
/-
Manure
24%
Harvesting
residues
3%/
Landfill
2%
Landscape
(
Wastewater
Municipal
wastes
50/
3%
Industrial
wastes
2%
Figure 5: Potential Sources of Biogas Production in Germany (Total Energy Potential of 417
PJ/Year)140
Figure 5 illustrates the energy potential of biogas in Germany. This country is among the most
advanced nations in organic waste management. As presented in Figure 4, the majority of the
energy potential comes from energy crops followed by animal manure. Note that this chart
represents the potential, which should not be confounded with the current practice.
/
Food-Processing
Wastewater
22%
_,Food Waste
2%
Food-Processing
Residues
10%
Night Soil Sludge
5%
Livestock Manure
4%
Figure 6: Feedstock Used in some Anaerobic Digesters in Japan14 1
140
141
Weiland, 2010, p. 853
Zhang, Itakura, & Matsuto, 2012, p. 14
47
Figure 6 breaks down the feedstock used in anaerobic digesters in Japan from a study conducted
by Zhang et al. (2012) on 42 plants. The chart is based on a total of 1.8 million tons per year
processed. Contrary to the previous observations in Germany, sewage sludge and foodprocessing waste contribute to almost 90% of the feedstock of these plants in Japan. However, it
is important to mention that only a fraction of the operating anaerobic digestion infrastructure is
shown and it does not represent the full picture.
The plants located in North America covered in the initial overview also present a great
feedstock variety. The facility in Oakland, California treats food waste from the commercial
sector.142 The two anaerobic digesters owned by the city of Toronto, Ontario operate with
commercial and residential organic waste sorted at the source.143 The feedstock of the plant in
London, Ontario is composed of food waste from restaurants, grocery stores and food processing
plants.144 Finally, the anaerobic digester located in Richmond, BC treats high-solids municipal
and industrial organic waste.145
This overview brings into perspective the wide range of possibilities in anaerobic digestion.
Numerous nations transform all kinds of biomass into energy. The selection of feedstock
depends on the regional economic, environmental and social factors.
2.4
2.4.1
INVESTIGATION
Procedure
The investigation has two major steps which are to describe the organic waste EBI already
manages and determine potential organic waste. Finally, a full picture is drawn in terms of
sustainability, availability, digestibility, impurities and inhibitors. This section is not intended to
recommend any type of organic material.
2.4.2
Organic Waste Currently Managed by EBI
As an integrated waste management company, EBI already receives a lot of organic waste from
numerous origins. Table 14 is a comprehensive summary of rounded quantities of organic waste
142 ILSR, 2010, p.
5
43 ILSR, 2010, p. 7
"Anaerobic Digest," 2013, p. 18
145 Harvest Power,
n.d.
144
48
received in 2013 with the type of organic waste, the source and the current treatment. The
quantities of organic waste from industrial sources are rounded values. A detailed version is
provided in Appendix B where the precise quantities, the client and location can also be found.
In most of the cases, the collection of organic waste has a seasonal variation. A description of
each type is in the paragraphs below.
Table 14: Quantities of Organic Waste Managed by EBI in 2013
Type of Waste
a. Food waste
Lawn Clippings
Leaves
Whey Permeate
Wasted Activated
Sludge
f. Dewatered Septic
Systems Sludge
g. Grease Trap Waste
b.
c.
d.
e.
h. Food Processing
Organic Waste
i. Liquid Yeast
Source of Waste
13,010
Residential
Commercial
Institutional
Residential
Residential
Industrial
Sewage
Septic Systems
Current
Treatment
None
8,400
4,270
2,500
1,180
Composting
Composting
Fertilizer
Landfilling
1,100
Landfilling
Commercial
Industrial
Industrial
500
Composting
250
Composting
Industrial
100
Composting
31,310
TOTAL
a.
Quantity of Organic
Waste (MT/year)
Food Waste
Food waste is collected from residential, commercial and institutional sectors. Figure 7 illustrates
a pile of this organic material where, among others, fruits, vegetables, dairy products, cereals and
meat compose the mix. During summer, people mix some lawn clippings in this waste while
leaves are found during fall. Indeed, a large quantity of contaminants is observed, mainly plastic
bags implying the need for pretreatment of this waste prior to anaerobic digestion. Currently,
EBI only piles this organic material and is unable to compost it due to its low purity.
49
Figure 7: Pile of Food Waste"
b.
Lawn Clippings
Lawn clippings are collected in even larger amounts during the late spring and summer. They are
initially in large plastic bags mechanically removed leading to a relatively pure organic matter.
Based on EBI's experience, lawn clippings have to be composted no later than a few days after
reception because strong odor can be emitted. Additionally, heat in the pile may become so high
that the organic material is burned and not compostable anymore. Contrarily to the leaves, it is
not possible to store lawn clippings for these reasons.
c.
Leaves
Large quantities of leaves are collected every year. Even if the collection is only during fall, this
feedstock is easily stored outside and used all year to produce compost. Similarly to lawn
clippings, they are received in large plastic bags which are mechanically removed to obtain a
significantly pure result shown in Figure 8.
146
Photo from site visit on 1/30/2014.
50
Figure 8: Pretreated Leaves Stored Before Being Composted"'
d.
Whey Permeate
Whey permeate is an industrial waste from dairy products. It is mostly liquid with approximately
7% dry matter and it is currently thickened with wood chips twice to be composted. This is a
costly and ineffective process. Anaerobic digestion may be an enhanced treatment for this type
of feedstock. Whey permeate is irregularly delivered in trucks with a capacity of 30 M 3 . The
number of loads depend on the production but may vary from one to five per week.
e.
Wasted Activated Sludge
48
Activated sludge is composed of aerobic microorganisms and organic solids from wastewater.1
A fraction is wasted periodically by wastewater treatment plants in the regional area which is
brought to EBI's landfill usually once a week. The wasted activated sludge is fairly constant over
the course of a year.
f.
Dewatered Septic Systems Sludge
EBI has a treatment plant receiving septic systems sludge with about 2% dry matter. After the
treatment, the sludge has nearly 40% dry matter. The wastewater is sent to the wastewater
treatment plant and the dewatered sludge goes to the landfill. The dewatering process costs about
$10 per ton, but a fee of $15 per ton is received; pretreatment represents about two thirds of the
fee received. Figure 9 illustrates the quantities of effluent in 2012. Indeed, this feedstock is
seasonal with peaks in spring and fall and a substantial drop during winter.
47 Photo from site visit on 1/30/2014.
148
Tchobanoglous, Wastewater Engineering: Treatment and Reuse, 661.
51
Wastewater
6000
Dewatered
Sludge
5000
4000
3000
2000
1000
0
Jan
Feb
March
April
May
June
July
Aug
Sept
Oct
Nov
Dec
Figure 9: Effluents from Septic Systems Sludge Treatment Plant in 201249
g.
Grease Trap Waste
Grease traps are devices preventing cooking residues from going to the sewage system. These
residues can come from a large number of sources and their composition depends on their origin.
As of now, EBI thickens the material with wood chips to compost it, similarly to the process
used for whey permeate. This type of organic waste is collected all year. Mario Brunelle, General
Manager at Leveill6 Fosses Septiques, a septic systems sludge collection company owned by
EBI, claims that many restaurants currently discharge their grease trap waste in sewage systems.
Still according to him, some regulations may be adopted in the near future to prevent this
practice which may increase significantly the quantities available.
h.
Food Processing Organic Waste
EBI receives organic waste from food processing industries which is currently composted with a
process similar to that used with whey permeate. This material is variable; it can be an expired
batch of jam or dressing for instance. Still, it has a high purity which is a good advantage. Small
quantities are constantly received in barrels at EBI's transshipment center in Montreal and
workers with a forklift handle and empty each one of them which is considered as an expensive
14 9 EBI
52
pretreatment. Finally, the organic waste is sent to the composting platform when there is a full
truck load once or twice every month.
i.
Liquid Yeast
Liquid yeast is an industrial waste originating from a food processing industry. Gerardi mentions
that yeast can be added if a scarcity in micronutrients exists. The suggested minimum quantity to
add is 1.5 kg/m3. 15 0 In EBI's situation, this feedstock is available and a fee is charged to the
client to treat it. However, EBI's client desires to minimize the amount of this end-product
discarded which results in highly intermittent deliveries. For instance, 37 m 3 of liquid yeast were
received in January 2014 and the next supply may be in one to twelve months according to Eric
Girard, Sales Manager from EBI.
Potential Feedstock
2.4.3
This section relates to unsorted feedstock that EBI may already collect, to feedstock that is
currently managed by other companies and to energy crops.
2.4.3.1
Organic Waste Unsorted or Managed by Other Companies
EBI has other potential options for obtaining organic waste to use in anaerobic digestion which
are summarized in Table 15. Detailed information is provided in Appendix C. Each type of
feedstock is described below Table 15.
Table 15: Quantities of Organic Waste Unsorted or Managed by Other Compani,
Quantity of
Type of Waste
a. Poultry Manure
No
Industrial
Initial
Quantity
(MT/year)
8,000
b. Rinsing Water
No
Industrial
2,500
100
2,500
from Food
Processing
Industry
c. Food waste
Yes
Restaurants
Grocery Stores
1,200
65
780
d. Straw
No
Agricultural
Unknown
100
-
Source of
Waste
Organic Waste
(MT/year)
8,000
11,280
TOTAL
150
Estimated
Organic
Fraction (%)
100
Managed
by EBI
Gerardi, The Microbiology of Anaerobic Digesters, 96.
53
a.
Poultry Manure
Poultry manure from a major chicken slaughterhouse is another interesting feedstock EBI can
potentially treat. The facility is located less than 10 km away from EBI's site. Years ago, their
manure was sent in the sewage system, but the government decided to prohibit this practice.
Currently, the chicken slaughterhouse transports its organic waste more than 200 km to an
anaerobic digester in Ontario. Based on EBI's past experiences composting such a waste, odor
emissions are very strong explaining the decision to stop treating it. In contrast to EBI's open-air
composting platform, an anaerobic digester is a closed process where odor may be managed
more easily. Nonetheless, it is a major concern needing consideration if this feedstock is
recommended.
b.
Rinsing Water from Food Processing Industry
Regarding the industrial sector, a food processing company presently transports its rinsing water
to a regional farm. As EBI is in charge of other organic wastes produced by this company, it may
be possible to receive this additional feedstock which represents significant quantities. Rinsing
water from their facility is delivered two or three times per week in large containers.
c.
Food Waste
The potential of food waste from the commercial sector is currently not completely captured. As
shown in Section 2.4.2, some restaurants and grocery stores already sort their organic material.
However, a great number of them still discharges all their waste to the landfill. Table 15 details
the quantities received in 2013 from such stores. Recyc-Quebec, a governmental organization
managing recycling in the province of Quebec, reported that about 65% of the waste originating
from restaurants and grocery stores is organic material. 5 1 This fraction is used to estimate the
quantities of organic waste these commercial clients may produce.
d.
Straw
Straw may also be available locally. EBI's site is located in an agricultural area where straw is
either left in the fields or used as a litter for livestock by farmers. The exact quantities EBI may
receive are unknown, but this material may be found locally.
151
Taillefer, Les matibres organiques Fiches informatives,
5.
54
2.4.3.2
Energy Crops
This section is an overview of the potential to grow energy crops for EBI. At first glance, it
seems like the perfect ingredients to harvest crops intended for anaerobic digestion are found at
EBI's site. The company uses just over 10% of the heat generated at the cogeneration plant and
releases to the atmosphere all of the carbon dioxide produced by the generators, rejects
approximately 1,000 cubic meters of treated leachate daily, generates large quantities of
compost, and has plenty of area available surrounding the existing infrastructure. Slade mentions
that over 50% cost reduction is possible when carbon dioxide, nutrients and water are cheaply
available which reflects EBI's situation. However, some major improvements are necessary
along most of the supply chain to obtain a reasonable cost, a positive energy balance and low
environmental impacts in a large-scale digestion unit. 5 2 Another concern related to growing
energy crops is the climate in Quebec. It is not possible to achieve the high efficiencies of
equatorial zones due to cold weather and the short growing period.
In addition to the technological and climatic limitations, energy crops raise justified ethical
concerns over the role of farmers in society and use of arable lands. The constantly growing
population represents a great pressure on food needs around the globe. The areas used to grow
energy crops instead of food crops limit land availability and create a scarcity which drives
prices up. Even if this practice is presently done at many places around the world, it may be
considered immoral to divert crops from food to energy.1
2.4.4
Composition of Organic Waste
The parameters of interest for each type of organic waste are presented in this section. Initially,
the internal composition is shown and discussed. Next, external factors that may have an
influence in the further analysis are illustrated.
The usual procedure is to pursue the analysis of samples of each source of organic waste and
determine the fraction of dry matter, the nutrient content, as well as their digestibility and purity.
EBI, its clients, and potential clients provided the data they have which is incomplete and the
other values are from the literature. This method is considered an acceptable estimate for an early
stage project. Table 16 and Table 17 summarize the characterization of the organic waste
152
1
Slade and Bauen, "Micro-Algae Cultivation for Biofuels," 29.
Wellinger, Murphy, and Baxter, The Biogas Handbook, 2013, 24-27.
55
previously described. Moreover, Appendix D illustrates other partial data on the chemical
composition of some types of organic waste. Due to the lack of laboratory analysis, some values
are unfortunately missing and no conclusion can be drawn on the presence of inhibitors.
56
29.4-47.8
63.2-77.9
54.0-99.0
226.8-243.0
A. I."
1"4
EBI; Carucci et al., "Anaerobic Digestion of Food Industry Wastes," 1039.; Wellinger, Murphy, and Baxter, The Biogas Handbook, 2013, 22.
155 EBI's Client; "PlanET Biogaz France."; Cornell Waste Management Institute, "App. A Characteristics of Raw Materials Table A. ."
156 Zhao and Ruan, "Biogas Performance from Co-Digestion of Taihu Algae and Kitchen Wastes," 22.; Alkanok, Demirel, and Onay, "Determination of Biogas
Generation Potential as a Renewable Energy Source from Supermarket Wastes," 136-139.
157 Long et al., "Anaerobic Co-Digestion of Fat, Oil, and Grease (FOG)," 234.; Silvestre et al., "Biomass Adaptation over Anaerobic Co-Digestion of Sewage
Sludge and Trapped Grease Waste," 6831.
158 Wellinger, Murphy, and Baxter, The Biogas Handbook, 2013, 22.; "PlanET Biogaz France."; Cornell Waste Management Institute, "App. A Characteristics of
Raw Materials Table A. L."
159 Wellinger, Murphy, and Baxter, The Biogas Handbook, 2013, 21-25.; Cornell Waste Management Institute, "App. A Characteristics of Raw Materials Table
Methane Production
(m CH 4/MT)
(M
CH 4/MT VS)
469.8
900
400
3
127.6
54
18
15
7.4
52.2
32
420-450
90
90
98
73.5
90
84
300-550
60
20
15
10
58
38
Dry Matter(%)
Volatile Solids
(% of Dry Matter)
Volatile Solids (%)
Methane Yield
430-530
4.1-5.9
-
5.0
7.5
4.5
6.9
pH
Organic Content
400-650
40-80
9-25
10-39
18
4-28
C/N Ratio (/N)
14
3,200
COD (mg/L)
Carbohydrates,
lipids
-
Carbohydrates,
lipids
-
fats, oils and
grease
15,000
Carbohydrates,
proteins, lipids
-
Leaves159
Lawn5 8
Clippings
Grease
Trap
s15
Parameter
Food waste156
Waste
Type of Waste
Food
Processing
Organic
5
Waste15
Carbohydrates,
proteins, lipids
24,700
Dewatered
Septic
Systems
Sludge' 54
Table 16: Composition of Organic Waste (1 of 2)
00
53.7
CH 4/MT)__________________________
128.3
900
95
14.3
15
4.5
23
114.0-463.6
150-610
95
76
80
4.4
48-150
15.0
400
75
3.75
5
7.0
9
-
Activat1e6
Sludge
Wasted
Whey
14.9-24.3
_____
330-540
64
5
7
4.5
5
75-80% lactose,
20-25% protein
-
Permeate'6 5
162 EBI's Client; "PlanET Biogaz France."
163 Wellinger, Murphy, and Baxter, The Biogas Handbook, 2013, 21-25.; "PlanET Biogaz France.";
Borgstr6m, Pretreatment Technologies to Increase the
Methane Yields by Anaerobic Digestion in Relation to Cost Efficiency of Substrate Transportation.Cornell Waste Management Institute, "App. A Characteristics
of Raw Materials Table A. L."
164 Perron and H6bert, "Caract6risation des boues d'6puration municipales Partie I: Parambtres agronomiques," 50.
165 EBI's Client; Wellinger, Murphy, and Baxter, The Biogas Handbook, 2013, 21.; Ykema et al., "Optimization of Lipid Production in the Oleaginous Yeast
Apiotrichum-Curvatum in Whey-Permeate," 213.; Mwangi, Gatebe, and Ndung'u, "Impact of Nutritional (C," 138.
161 EBI's Potential Client; Wellinger, Murphy, and Baxter, The Biogas Handbook, 2013, 21.
160 EBI's Client; "PlanET Biogaz France."; Anderson et al., "Pilot- and Full-Scale Anaerobic Digestion for the Food and Drink Industry," 286.
(in 3
Methane Production
97.2-145.8
300
CH 4/MT VS)
600-900
3
94.7
17.9
90
16.2
(M
19
18
Dry Matter(%)
Volatile Solids
(% of Dry Matter)
Volatile Solids (%)
Methane Yield
5.5
5.7
pH
74
Carbohydrates,
lipids
-
Carbohydrates,
proteins, lipids
-
Carbohydrates,
proteins, lipids
188,190
50% proteins,
10 % trehaloses
6,700
4
Straw
Processing
Industry162
Manure161
Yeast6"
163
from Food
Poultry
Rinsing Water
Type of Waste
Liquid
C/N Ratio (/N)
COD (mg/L)
Organic Content
Parameter
Table 17: Composition of Organic Waste (2 of 2)
In addition to the internal composition of each feedstock, other aspects need to be covered. Table
18 is a summary of the fee received by EBI to treat the waste, the current treatment, the current
and projected transportation, as well as the cost of pretreatment. Indeed, all the fees but the one
for poultry manure are the current values and may be adjusted with further economic analysis.
Note that the fee for poultry manure is an estimate and needs to be negotiated with the company
operating the facility if the project occurs. It is set to a high price because the current treatment
involves large transportation costs; EBI has leverage to charge a good fee to receive this
feedstock. The cost of food waste pretreatment is a discounted estimate from a feasibility study
for the anaerobic digestion project in Toronto. 6 6 The other pretreatment costs are provided by
EBI.
Table 18: Fee, Current Treatment, Current and Projected Transportation and Pretreatment Costs
of Organic Waste
Transportation (km)
Fee
($/MT)
Current
Treatment
15.00
Landfilling
95.00
Composting
Lawn Clippings
Leaves
Liquid Yeast
60.00
75.00
60.00
60.00
56.00
None
Composting
Composting
Composting
Composting
Poultry Manure
100.00
Anaerobic
Digestion
Fertilizer
Type of Waste
Dewatered Septic
Systems Sludge
Food Processing Organic
Waste
Food Waste
Grease Trap Waste
Rinsing Water from Food
Processing Industry
95.00
Straw
None
Wasted Activated Sludge
Whey Permeate
51.00
95.00
Litter for
imals
Landfilling
Fertilizer
Current
Projected
Regional Collection
80
Regional
Regional
Regional
Regional
90
>200
100
80
Collection
Collection
Collection
Collection
90
10
Pretreatment
for Anaerobic
Digestion
($/MT)
10
30
20
12
37
-
80
Local Collection
-
Regional Collection
80
70
-
Allen Kani Associates with Enviros RIS Ltd., WDO Study: Implications of Different Waste Feed Streams
(Source-Separated Organics and Mixed Waste) On Collection Options and Anaerobic Digestion Processing
Facility Design, Equipment and Costs, 30-31.
166
59
2.5
POTENTIAL MIXES
Once all the ingredients available or potentially available to EBI are known, recipes have to be
assembled. Various mixes of feedstock are set in order to analyze them. The current section
initially defines the total capacity the infrastructure may have in order to respect EBI's
constraints. Next, the equations to calculate the parameters of the mixes are defined. Finally, the
probable feedstock combinations are formed and described. They are compared with a multicriteria analysis (MCA) in Section 2.6.
2.5.1
Total Capacity
The main constraint influencing the capacity of the anaerobic digester for EBI is the desire to
invest a maximum amount of $1 million.
50
45
Z 40
0
C
(P 25
E 20
a~
15
C
10
5
0
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
CapaCity (X 103 MT/year)
Figure 10: Initial Investment over Annual Capacity for Anaerobic Digestion Projects 67
Figure 10 can be used to estimate the annual capacity of the plant. Unfortunately, the graph
presents much larger values than the scale EBI desires and it is hard to read a value for an initial
167
Laforest, "Facteurs de rentabilite des projets de biomethanisation,"
14.
60
investment of $1
million. However, by assuming that approximately a $5 million initial
investment is necessary for about 3,000 annual tons and assuming a linear relation on that
portion of the graph, an estimate of $1,667 per ton can be made. By contrast, capital costs
reported by the Institute for Local Self-Reliance for different sites in Toronto, Canada show a
range of $300 to $900 per ton 16 which is a large contrast with Laforest's value. From these
assumptions, EBI's anaerobic digester can have an annual capacity between 600 tons and 3,300
tons. Based on the existing infrastructure of the company on one side and on the desire to remain
conservative on the other side, an annual capacity between 1,000 and 2,000 tons is judged
reasonable and may become more precise in further phases of the project.
2.5.2
Calculation of Parameters
The parameters used to evaluate the options are C/N ratio, dry matter fraction, pH and methane
production. This section covers the calculations done to obtain each value. These are estimates to
compare the combinations.
The C/N ratio and dry matter fraction of a specific mix is obtained with a weighted average of
the parameters of each component as shown in Equation 1 and Equation 2.
Equation 1: Calculation of C/N Ratio of Multiple Substrates
C'N
al
=
C/Ni x Massi
T Massi
Equation 2: Calculation of Dry Matter Fraction of Multiple Substrates
Dry MatterTotal
Dry Matteri x Massi
Z Massi
The calculation of pH cannot be done in the same way because it is the negative logarithm of a
concentration as illustrated in Equation 3. Therefore, the H+ ion concentrations is calculated for
each component of a given mix and a weighted average is calculated from the ion concentrations.
Finally, the negative logarithm of the total concentration is calculated to obtain the pH of a
feedstock combination. Equation 4 and Equation 5 summarize the steps to obtain this value. This
may not be an exact calculation as pH depends on a large number of factors and chemical
168
"Update on Anaerobic Digester Projects Using Food Wastes in North America," 8.
61
reactions may occur when the substrates are mixed. Nonetheless, this method is considered as an
acceptable estimate in the context of an early project evaluation.
Equation 3: Definition of the pH' 69
pH = -log[H+]
Equation 4: Calculation of H+ Ions Concentration of Multiple Substrates
[H+]Total
SE[H+]i
x Mass.
Mas
-
E Massi
Equation 5: Calculation of pH from H+ Ions Concentration of Multiple Substrates
pHTotaL =
-log[H+ota
Using Equation 6, the methane yield is converted to methane production using the volatile dry
matter fraction (VDM). Then, Equation 7 is a weighted average done to obtain the methane
production of a combination. Finally, the annual methane production is calculated by multiplying
the production per mass by the mass per year as shown in Equation 8.
Equation 6: Conversion of Methane Yield per Volatile Dry Matter to Methane Production by Mass
CH4 Production
(Volume
Volume
Mass VDM
Mass) = CH 4 Yield (Mass VDM) x VDM
Mass
(
Equation 7: Calculation of Methane Production per Mass of Multiple Substrates
(Volume
CH 4 ProductionTotai
.(Volume
E CH 4 Productioni MVolm
ass e x Massi
=
(Mass
Massi
169 Mihelcic, Fundamentals of Environmental Engineering 1st (first) Edition by Mihelcic, James R. Published by
Wiley, 86.
62
Equation 8: Calculation of Methane Production per Time of Multiple Substrates
(Volumes
CH 4 Productionrotai Time
Time
Volume~ L Mass1
CH 4 ProductionTotalIVu
Mass
X
Time
As mentioned before, codigestion, the simultaneous treatment of different types of organic
waste, can improve digestibility. However, this effect is ignored in the calculations for several
reasons. Such a phenomenon is more likely to be observed in laboratory experiments than in
large scale digesters probably because parameters tend to differ from the ideal reactions in the
latter case.170 Moreover, it is hard to theoretically quantify this effect due to the fact that all the
mixes proposed are unique and no data exist regarding the combination of these precise types of
waste. It is considered that ignoring the potential for enhanced digestibility represents a
conservative assumption and may not significantly impact the ranking of the mixes.
2.5.3
Formation of the Mixes
This process is iterative, but presented as a whole. The objective is to create and compare the
potential optimal mixes. To facilitate operations and ensure the mixes can be pumped, dry matter
fraction is kept below 15%.'1'
Additionally, pH is held over 6.0 to provide a suitable
environment for microorganisms.172 All the mixes include liquid yeast because it is a good
source of micronutrients which may enhance digestion.173 The quantity in each mix is set to 50
tons, but the exact amount to add may be optimized with laboratory experiments and field
experience. The number of possibilities being very large, a first iteration is done with thirteen
mixes where the organic wastes below 15% dry matter are not combined. From the initial results,
Mix 14 and Mix 15 are then created; they are variations of the optimal solution of the first
attempt. These two mixes are incorporated to the analysis presented in Section 2.6.
Some wastes were excluded from the mixes for different reasons. Lawn clippings are not
considered due to their high seasonality and the storage difficulties encountered by EBI. Straw is
set aside due to its high lignin content which reduces methane yield; no economically viable
Long et al., "Anaerobic Co-Digestion of Fat, Oil, and Grease (FOG)," 239.
Steven Thomas Sell, "A Scale-up Procedure for Substrate Co-Digestion in Anaerobic Digesters through the Use
of Substrate Characterization, BMPs, ATAs, and Sub Pilot-Scale Digesters," 21.
172 Speece, Anaerobic Biotechnology for Industrial Wastewaters,
58.
173 Gerardi, The Microbiology of Anaerobic Digesters,
96.
170
171
63
pretreatment currently exists.1 74 Whey permeate is not considered because it is not possible, with
the feedstock available, to produce a mix solely with this waste as the liquid input and to obtain a
dry matter fraction under 15% combined with a pH over 6.0. This type of organic waste is
excessively acid which compromises its use as the only liquid feedstock. Still, a small amount of
whey permeate is added to Mix 15 to assess its potential.
2.5.4
Descriptions of Mixes
Fifteen feedstock combinations are formed respecting the range of capacity and parameters
defined previously. Figure 11 lists the mixes with the annual quantity of each component based
on pure content. This implies that losses due to pretreatment already occurred. The six initial
mixes use wasted activated sludge as the main component while food waste is the principal
ingredient in Mix 7 to Mix 13 and Mix 14 and 15 are created after the first iteration. The
combinations exhibit minor variations with dewatered septic systems sludge, food processing
organic waste, grease trap waste, leaves, poultry manure, rinsing water from the food processing
industry, wasted activated sludge and whey permeate. The specific quantities of each input can
be found in Appendix E.
Risberg et al., "Biogas Production from Wheat Straw and Manure - Impact of Pretreatment and Process
Operating Parameters," 232-237.
174
64
1,600
1,550
1.500 1,510
1,400
400 -
-1-ft
1,300
,27 5
_ 1 )00
1 20 0
,
1
0 Leaves
1,300
1,270
7 '
1,200
I
1,400
m Rinsing Water from
Food Processing
Industry
O
1,100
i 075
1,100
11A75
1,000
Poultry Manure
* Food Processing
Organic Waste
--
800
--
-
* Grease Trap Waste
O Dewatered Septic
600
Systems Sludge
E Wasted Activated
Sludge
400
N Food Waste
200
N Liquid Yeast
0
1
2
3
4
5
6
7
8
9
Mix
10
11
12
Figure 11: Annual Quantities of Organic Waste in each Mix
65
13
14
15
The technical parameters of the mixes are summarized in Table 19. Detailed values can be found
in Appendix E.
Table 19: Parameters Calculated for the Mixes
Mix
1. Wasted Activated Sludge and
Rinsing Water from Food
Processing Industry
2. Wasted Activated Sludge and
Grease Trap Waste
3. Wasted Activated Sludge,
Poultry Manure and Grease
Trap Waste
4. Wasted Activated Sludge,
Dewatered Septic Systems
Sludge and Grease Trap Waste
5. Wasted Activated Sludge and
Food Processing Organic Waste
6. Wasted Activated Sludge,
Grease Trap Waste and Leaves
7. Food Waste and Grease Trap
Waste
8. Food Waste and Rinsing
Water from Food Processing
Industry
9. Food Waste, Poultry Manure
and Grease Trap Waste
10. Food Waste, Dewatered
Septic Systems Sludge and
Grease Trap Waste
11. Food Waste, Dewatered
Septic Systems Sludge, Poultry
Manure and Grease Trap Waste
pH
9
6.1
6
9
6.3
14-15
3
(x10 m
CH 4/MT)
3
CH 4/year)
($/year)
20.4-22.4
26.1-28.5
66,375
6
20.0-22.5
26.0-29.2
67,750
6.1
7
22.4-24.7
31.4-34.6
77,750
10-12
6.1
15
49.8-52.3
77.2-81.1
67,300
9
6.2
6
25.4-27.3
32.3-34.7
65,900
9-11
5.7-6.4
7
23.8-26.5
28.6-31.8
62,275
17-18
6.2
11
34.0-53.6
37.4-59.0
66,550
17
6.1
10
34.9-54.2
37.5-58.3
65,175
22-23
6.1
11
35.7-53.6
42.8-64.3
76,550
17-18
6.3
15
48.4-65.0
62.9-84.5
69,550
21-22
6.2
15
48.8-64.2
68.3-89.9
79,550
6.1
11
42.8-62.1
46.0-66.8
65,175
18-19
5.7-6.4
12
37.7-57.4
41.5-63.1
66,175
20-21
6.2
14
46.5-60.9
69.8-91.4
84,650
20-21
6.1
14
46.3-60.7
70.0-91.6
85,600
ProcessingaOrganic Waste17-18
13. Food Waste, Grease Trap
Waste and Leaves
14. Food Waste, Dewatered
Septic Systems Sludge, Poultry
Manure, Wasted Activated
Sludge and Grease Trap Waste
15. Food Waste, Dewatered
Septic Systems Sludge, Poultry
Manure, Wasted Activated
Sludge, Grease Trap Waste and
Whey Permeate
(%)
Fee
Methane Production
Dry
Matter
C/N
Ratio
(/N)
66
(mn
2.6
MULTI-CRITERIA ANALYSIS (MCA)
Due to the large number of parameters and feedstock mixes to evaluate, a multi-criteria analysis
(MCA) is necessary to justify recommendations. Eight criteria are assessed in order to target the
optimal solutions: fee, diversion of waste, availability, odor, purity, suitability, digestibility and
inhibitors. The first five criteria are classified before treatment, while suitability, digestibility and
inhibitors are criteria considered during treatment. Each of them is explained in the following
sections and a performance note is attributed to every mix. Table 20 defines the score scale used
in the MCA. In the case it is not possible to obtain five different scores, the low end of the scale
is used such as with odor. Such procedure intentionally reduces the mathematical importance of
criteria with less variation. Additionally, it is essential to mention that the MCA is used as a way
to contrast the best mixes with the other mixes. The aim is not to precisely target the single best
mix, but to draw some general conclusions regarding a complex engineering problem.
Table 20: Score Scale of the MCA
Definition
Excellent
Very good
Good
Sufficient
Low
Score
5
4
3
2
1
Table 21 establishes the abbreviations used in the MCA to streamline the other tables.
Table 21: Abbreviations of the Types of Waste for the MCA
Type of Waste
Dewatered Septic Systems Sludge
Food Processing Organic Waste
Food Waste
Grease Trap Waste
Leaves
Poultry Manure
Rinsing Water from Food Processing Industry
Wasted Activated Sludge
Whey Permeate
67
Abbreviation
DSSS
FPOW
FW
GTW
Leaves
PM
RWFPI
WAS
WP
2.6.1
Before Treatment
The criteria before treatment include all operations required prior to anaerobic digestion from
transportation to storing to pretreatment. Additionally, the fee as well as the environmental
performance of the mixes are measured.
2.6.1.1
Fee
The fee is the amount of money EBI receives for each feedstock it manages. It is typically paid
on a mass basis. Table 22 illustrates the total fee of all the ingredients for each mix. The two
mixes providing the highest fees, 15 and 14 respectively, deserve a "very good" score. Mixes 11,
3 and 9 gamer slightly lower fees giving them a score of "good" while Mix 6 has the lowest fee
giving it a score of "low". The rest of the combinations are too close to be objectively sorted so
they all have a "sufficient" score.
Table 22: Score of the Mixes on the Criterion of Fee
Mix
Fear)
15. Food Waste, Dewatered Septic Systems Sludge, Poultry
Manure, Wasted Activated Sludge, Grease Trap Waste and Whey
Permeate
14. Food Waste, Dewatered Septic Systems Sludge,
Poultry
Manure, Wasted Activated Sludge and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems Sludge,
Poultry
Manure and Grease Trap Waste
3. Wasted Activated Sludge, Poultry Manure and Grease Trap
Waste
9. Food Waste, Poultry Manure and Grease Trap Waste
10. Food Waste, Dewatered Septic Systems Sludge and Grease
Trap Waste
2. Wasted Activated Sludge and Grease Trap Waste
4. Wasted Activated Sludge, Dewatered Septic Systems Sludge
and Grease Trap Waste
7. Food Waste and Grease Trap Waste
1. Wasted Activated Sludge and Rinsing Water from Food
Processing Industry
13. Food Waste, Grease Trap Waste and Leaves
5. Wasted Activated Sludge and Food Processing Organic Waste
8. Food Waste and Rinsing Water from Food Processing Industry
12. Food Waste and Food Processing Organic Waste
6. Wasted Activated Sludge, Grease Trap Waste and Leaves
68
Score
85,600
4
84,650
79,550
77,750
3
76,550
69,550
67,750
67,300
66,550
66,375
2
66,175
65,900
65,175
65,175
62,275
1
2.6.1.2
Diversion of Waste
Diversion of waste considers two main elements: treatment and transportation. The idea is to
evaluate the ingredients in each combination that are diverted from which treatment and the
difference in transportation requirements; this analysis is done in three steps. Initially, the
combinations obtain individual scores on treatment and transportation. Finally, the two scores are
averaged leading to an overall objective ranking of the mixes for the criterion of diversion of
waste.
As mentioned previously, all the mixes contain liquid yeast, diverted from composting which is
an equal factor in all cases. Table 23 shows the score attributed to the mixes for their treatment
diversion. Mix 4 has the best performance because it contains 1,400 annual tons of waste
currently landfilled, which is the largest quantity among the combinations. Mixes 1, 2, 3, 5 and 6
are scored as "good" due to their 1,100 tons to 1,200 tons per year diverted from landfilling.
With much smaller quantities of material heading to the landfill and the potential to find a viable
treatment for food waste, mixes 10, 11, 14 and 15 are considered as "sufficient". The rest of the
mixes all contain food waste as well, but it is combined with waste presently composted or used
as a fertilizer; hence a "low" performance score is given.
69
Table 23: Score of the Mixes on the Criterion of Diversion of Waste Specific to Treatment
Mix
4. Wasted Activated Sludge, Dewatered Septic
Systems Sludge and Grease Trap Waste
Diversion from Landfilling
(WAS/DSSS) and Composting (GTW)
1. Wasted Activated Sludge and Rinsing Water
from Food Processing Industry
2. Wasted Activated Sludge and Grease Trap
Waste
Diversion from Landfilling (WAS) and
Fertilizing (RWFPI)
Diversion from Landfilling (WAS) and
Composting (GTW)
3. Wasted Activated Sludge, Poultry Manure
and Grease Trap Waste
Diversion from Landfilling (WAS) and
from Composting (GTW)
5. Wasted Activated Sludge and Food
Processing Organic Waste
Diversion from Landfilling (WAS) and
Composting (FPOW)
6. Wasted Activated Sludge, Grease Trap Waste
and Leaves
Diversion from Landfilling (WAS) and
Composting (GTW/Leaves)
14. Food Waste, Dewatered Septic Systems
Sludge, Poultry Manure, Wasted Activated
Sludge and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems
Sludge, Poultry Manure, Wasted Activated
Sludge, Grease Trap Waste and Whey Permeate
10. Food Waste, Dewatered Septic Systems
Sludge and Grease Trap Waste
New Treatment (FW) and Diversion
from Landfilling (DSSS/WAS) and
Composting (GTW)
New Treatment (FW) and Diversion
from Landfilling (DSSS/WAS),
Composting (GTW) and Fertilizing (WP)
New Treatment (FW) and Diversion
from Landfilling (DSSS) and
Composting (GTW)
New Treatment (FW) and Diversion
from Landfilling (DSSS) and
Composting (GTW)
New Treatment (FW) and Diversion
from Composting (GTW)
11. Food Waste, Dewatered Septic Systems
Sludge, Poultry Manure and Grease Trap Waste
7. Food Waste and Grease Trap Waste
Diversion of waste (Treatment)
8. Food Waste and Rinsing Water from Food
Processing Industry
New Treatment (FW) and Diversion
from Fertilizing (RWFPI)
9. Food Waste, Poultry Manure and Grease Trap
Waste
New Treatment (FW) and Diversion
from Composting (GTW)
12. Food Waste and Food Processing Organic
Waste
New Treatment (FW) and Diversion
from Composting (FPOW)
13. Food Waste, Grease Trap Waste and Leaves
New Treatment (FW) and Diversion
from Composting (GTW/Leaves)
Score
3
2
Table 24 illustrates the scores related to the impact the project may have in terms of
transportation. Mixes 3, 9, 11 and 14 obtain the highest score because they contain poultry
manure which currently travels over 200 km to be treated in an anaerobic digester in Ontario,
Canada and the chicken slaughterhouse is located only 10 km away from the projected location
of EBI's anaerobic digester. Mix 15 receives a "good" grade, which is lower than the previous
70
mixes; it contains poultry manure as well, but transportation of whey permeate is going to
increase by about 10 km. Judged as "sufficient", Mix 1 and Mix 8 imply approximately a 20 km
reduction in the transportation of rinsing water from the food processing industry. Finally, the
other mixes are ranked "low" because all the material is already shipped to EBI's site so the
anaerobic digestion project has no impact on transportation of these wastes.
Table 24: Score of the Mixes on the Criterion of Diversion of Waste Specific to Transportation
Mix
Diversion of waste
(Transportation)
3. Wasted Activated Sludge, Poultry Manure and Grease
Trap Waste
9. Food Waste, Poultry Manure and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems Sludge, Poultry
Manure and Grease Trap Waste
14. Food Waste, Dewatered Septic Systems Sludge, Poultry
Manure, Wasted Activated Sludge and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems Sludge, Poultry
Manure, Wasted Activated Sludge, Grease Trap Waste and
Whey Permeate
1. Wasted Activated Sludge and Rinsing Water from Food
Processing Industry
8. Food Waste and Rinsing Water from Food Processing
Industry
2. Wasted Activated Sludge and Grease Trap Waste
4. Wasted Activated Sludge, Dewatered Septic Systems
Sludge and Grease Trap Waste
5. Wasted Activated Sludge and Food Processing Organic
Waste
6. Wasted Activated Sludge, Grease Trap Waste and
Leaves
7. Food Waste and Grease Trap Waste
10. Food Waste, Dewatered Septic Systems Sludge and
Grease Trap Waste
12. Food Waste and Food Processing Organic Waste
13. Food Waste, Grease Trap Waste and Leaves
High Reduction (PM)
71
High Reduction (PM)
High Reduction (PM)
Score
4
High Reduction (PM)
High Reduction
(PM), Low Increase
(WP)
Low Reduction
(RWFPI)
Low Reduction
(RWFPI)
No Effect
No Effect
No Effect
No Effect
No effect
No effect
No Effect
No Effect
3
2
Following the individual analysis of treatment and transportation diversion, Table 25 represents
the average score of the criterion. Mix 3 obtains the best performance on diversion of waste.
Table 25: Average Score of the Mixes on the Criterion of Diversion of Waste
Mix
3. Wasted Activated Sludge, Poultry Manure and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure and
Grease Trap Waste
14. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure,
Wasted Activated Sludge and Grease Trap Waste
1. Wasted Activated Sludge and Rinsing Water from Food Processing
Industry
4. Wasted Activated Sludge, Dewatered Septic Systems Sludge and Grease
Trap Waste
9. Food Waste, Poultry Manure and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure,
Wasted Activated Sludge, Grease Trap Waste and Whey Permeate
2. Wasted Activated Sludge and Grease Trap Waste
5. Wasted Activated Sludge and Food Processing Organic Waste
6. Wasted Activated Sludge, Grease Trap Waste and Leaves
8. Food Waste and Rinsing Water from Food Processing Industry
10. Food Waste, Dewatered Septic Systems Sludge and Grease Trap Waste
7. Food Waste and Grease Trap Waste
12. Food Waste and Food Processing Organic Waste
13. Food Waste, Grease Trap Waste and Leaves
2.6.1.3
Average
Score
3.5
3.0
2.5
2.0
1.5
1.0
Availability
Availability of the feedstock relates to the seasonal variations of the reception of each waste.
This element has a direct influence on storage requirements. Distance of transportation is ignored
in the current criterion because the vast majority of the waste originates from local and regional
sources and only a few variations exist in this regard. Additionally, transportation is partly
included in diversion of waste, the prior criterion. Table 26 displays the scores of the fifteen
combinations. Rated as "very good", Mix 1 and Mix 8 contain waste received on a regular basis
all year. Next, mixes 2, 3, 5, 7, 9, and 12 are relatively consistent over the course of a year with
some minor variations on grease trap waste and food processing organic waste. Even though
leaves are very seasonal, their storage is easy and inexpensive which justifies the "sufficient"
72
grade of Mix 6 and Mix 13. The other mixes, 4, 10, 11 14 and 15, obtain a "low" performance
score due to the high seasonality of septic systems sludge.
Table 26: Score of the Mixes on the Criterion of Availability
Mix
1. Wasted Activated Sludge and Rinsing
Water from Food Processing Industry
8. Food Waste and Rinsing Water from Food
Processing Industry
2. Wasted Activated Sludge and Grease Trap
Waste
3. Wasted Activated Sludge, Poultry Manure
and Grease Trap Waste
5. Wasted Activated Sludge and Food
Processing Organic Waste
7. Food Waste and Grease Trap Waste
9. Food Waste, Poultry Manure and Grease
Trap Waste
12. Food Waste and Food Processing
Organic Waste
6. Wasted Activated Sludge, Grease Trap
Waste and Leaves
Availability (Seasonality)
All year
4
All year
All year with minor variations (GTW)
All year with minor variations (GTW)
All year with minor variations (FPOW)
All year with minor variations over year
(GTW)
All year with minor variations over year
(GTW)
All year with minor variations (FPOW)
3
Mostly Fall (Leaves) and minor
variations over year (GTW)
13. Food Waste, Grease Trap Waste and
Leaves
Mostly Fall (Leaves) and minor
variations over year (GTW)
4. Wasted Activated Sludge, Dewatered
Septic Systems Sludge and Grease Trap
Waste
10. Food Waste, Dewatered Septic Systems
Sludge and Grease Trap Waste
Mostly Summer for DSSS and minor
variations over year (GTW)
11. Food Waste, Dewatered Septic Systems
Sludge, Poultry Manure and Grease Trap
Waste
14. Food Waste, Dewatered Septic Systems
Sludge, Poultry Manure, Wasted Activated
Sludge and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems
Sludge, Poultry Manure, Wasted Activated
Sludge, Grease Trap Waste and Whey
Permeate
Mostly Summer for DSSS and minor
variations over year (GTW)
2.6.1.4
Score
2
Mostly Summer for DSSS and minor
variations over year (GTW)
Mostly Summer for DSSS and minor
variations over year (GTW)
Mostly Summer for DSSS and minor
variations over year (GTW)
Odor
Odor is considered as the main social constraint of the project. EBI particularly wishes to avoid
odor spreading large distances to the neighbors. All wastes smell on a short distance, but it has a
lesser importance in terms of social impact. Additionally, the odor emissions are directly
73
influenced by the weather conditions which vary significantly. However, parameters such as
short range odor and weather conditions are considered equal in all the mixes. Based on the
experience of Gilles Denis, General Manager at Dep6t Rive-Nord, a division of EBI in charge of
the landfill, poultry manure is the waste with the worst odor emissions because they are intense,
they last a long time and they are capable of spreading over long distances. No scientific
evidence is considered for the current criterion, but field experience is judged reliable. As
observed on Table 27, mixes 3, 9, 11, 14 and 15 are ranked "low" due to the presence of poultry
manure. Specific measures may be required to control odor in these cases. The rest of the
combinations are all judged equal with a "sufficient" score.
Table 27: Score of the Mixes on the Criterion of Odor
Mix
1. Wasted Activated Sludge and Rinsing Water from Food
Processing Industry
2. Wasted Activated Sludge and Grease Trap Waste
4. Wasted Activated Sludge, Dewatered Septic Systems Sludge
and Grease Trap Waste
5. Wasted Activated Sludge and Food Processing Organic Waste
6. Wasted Activated Sludge, Grease Trap Waste and Leaves
7. Food Waste and Grease Trap Waste
8. Food Waste and Rinsing Water from Food Processing Industry
10. Food Waste, Dewatered Septic Systems Sludge and Grease
Trap Waste
12. Food Waste and Food Processing Organic Waste
13. Food Waste, Grease Trap Waste and Leaves
3. Wasted Activated Sludge, Poultry Manure and Grease Trap
Waste
9. Food Waste, Poultry Manure and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems Sludge,
Poultry
Manure and Grease Trap Waste
14. Food Waste, Dewatered Septic Systems Sludge, Poultry
Manure, Wasted Activated Sludge and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems Sludge, Poultry
Manure, Wasted Activated Sludge, Grease Trap Waste and Whey
Permeate
2.6.1.5
Odor
Low
Score
Low
Low
Low
Low
Low
Low
Low
2
Low
Low
High for PM
High for PM
High for PM
High for PM
High for PM
Purity
Purity is affected by the amount of non-biodegradable material in the feedstock as it is received,
which directly relates to pretreatment requirements. Leaves, septic systems sludge and food
74
processing organic waste are already pretreated as part of their current treatment so the data
come from EBI. As described previously, food waste is a significantly contaminated feedstock
and the numerical value of the cost of sorting the material is taken from the literature.1 75
Pretreatment necessities as well as performance scores for all the mixes appear in Table 28. None
of the ingredients of mixes 1, 2 and 3 involve pretreatment, so a "high" score is attributed. Mixes
4, 5, and 6 all have a secondary ingredient necessitating pretreatment so they are graded as
"good". The main constituent of mixes 7, 8 and 9 is food waste which requires pretreatment, but
no other input needs to go through this operation. Thus, they are evaluated as "sufficient".
Finally, mixes 10, 11, 12, 13, 14 and 15 include two components involving pretreatment
justifying the "low" score.
Table 28: Score of the Mixes on the Criterion of Purity
Mix
Mix
1. Wasted Activated Sludge and Rinsing Water from Food
Processing Industry
2. Wasted Activated Sludge and Grease Trap Waste
3. Wasted Activated Sludge, Poultry Manure and Grease Trap Waste
4. Wasted Activated Sludge, Dewatered Septic Systems Sludge and
Grease Trap Waste
5. Wasted Activated Sludge and Food Processing Organic Waste
6. Wasted Activated Sludge, Grease Trap Waste and Leaves
7. Food Waste and Grease Trap Waste
8. Food Waste and Rinsing Water from Food Processing Industry
9. Food Waste, Poultry Manure and Grease Trap Waste
10. Food Waste, Dewatered Septic Systems Sludge and Grease Trap
Waste
11. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure
and Grease Trap Waste
12. Food Waste and Food Processing Organic Waste
13. Food Waste, Grease Trap Waste and Leaves
14. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure,
Wasted Activated Sludge and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure,
Wasted Activated Sludge, Grease Trap Waste and Whey Permeate
PurityScr
(Pretreatment)
Score
None
None
None
$10/MT (DSSS)
$30/MT
$37/MT
$20/MT
$20/MT
$20/MT
$20/MT
$10/MT
$20/MT
$10/MT
$20/MT
$30/MT
$20/MT
$37/MT
$20/MT
$10/MT
$20/MT
$10/MT
(FPOW)
(Leaves)
(FW)
(FW)
(FW)
(FW) and
(DSSS)
(FW) and
(DSSS)
(FW) and
(FPOW)
(FW) and
(Leaves)
(FW) and
(DSSS)
(FW) and
(DSSS)
2
Allen Kani Associates with Enviros RIS Ltd., WDO Study: Implications of Different Waste Feed Streams
(Source-Separated Organics and Mixed Waste) On Collection Options and Anaerobic Digestion Processing
Facility Design, Equipment and Costs, 30-31.
175
75
2.6.2
During Treatment
The criteria during treatment are vital to the project. Suitability, digestibility and inhibitors are
three parameters directly related to the performance of the consortium of bacteria in the
anaerobic digester. Each one of them is described and graded below.
2.6.2.1
Suitability
Suitability considers the quality of the internal environment of the anaerobic digester. The two
most common parameters used to evaluate this criterion are C/N ratio and pH. In practice, many
other factors are monitored to ensure a proper suitability, but C/N ratio and pH are adequate to
perform the current analysis due to the limited information available and the early stage of the
project. Each factor is evaluated individually before being compiled to obtain a global score for
suitability.
Table 29 illustrates an approximation of the C/N ratio of the mixes. As mentioned previously, the
optimal range is between 20/1 and 30/1 but lower values are acceptable. All the combinations are
either at the inferior end of the preferred range or below. They are ranked from highest to lowest
and graded accordingly. Mixes 9, 11, 14 and 15 have a C/N ratio between 20 and 30, so they
obtain an "excellent" score. Mixes 13, 7, 10, 12 and 8 are just under the lower end of the desired
range so a "very good" score is granted. Mix 3 and Mix 4 obtain a "good" and "sufficient" score
respectively whereas the rest of the mixes, 6, 2, 1, and 5, are considered "low" due to their poor
C/N ratio.
76
Table 29: Score of the Mixes on the Criterion of Suitability Specific to C/N Ratio
Mix
9. Food Waste, Poultry Manure and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure and
Grease Trap Waste
14. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure,
Wasted Activated Sludge and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure,
Wasted Activated Sludge, Grease Trap Waste and Whey Permeate
13. Food Waste, Grease Trap Waste and Leaves
Su11itabhilit
.7
(C/N Ratio)
22-23
21-22
20-21
18-19
17-18
10. Food Waste, Dewatered Septic Systems Sludge and Grease Trap Waste
17-18
12. Food Waste and Food Processing Organic Waste
17-18
4. Wasted Activated Sludge, Dewatered Septic Systems Sludge and Grease
Trap Waste
6. Wasted Activated Sludge, Grease Trap Waste and Leaves
2. Wasted Activated Sludge and Grease Trap Waste
1. Wasted Activated Sludge and Rinsing Water from Food Processing
Industry
5. Wasted Activated Sludge and Food Processing Organic Waste
5
20-21
7. Food Waste and Grease Trap Waste
8. Food Waste and Rinsing Water from Food Processing Industry
3. Wasted Activated Sludge, Poultry Manure and Grease Trap Waste
Score
4
17
14-15
3
10-12
2
9-11
9-10
9
1
9
The optimal pH reported by Speece is between 6.5 and 8.2, but it may be acceptable as low as
6.0. 76 The pH and performance score of the mixes on this parameter are found in Table 30. All
the combinations tend to the acid limit of the range, so this factor may need to be closely
examined in further tests. The mixes are sorted in descending order with Mix 2 and Mix 10
obtaining a "very good" score. Mixes 5, 7 and 11 have a "good" score with a pH estimated at
6.2. Next, mixes 1, 3, 4, 8, 9 and 12 have a pH of 6.1 which leads to a "sufficient" score. Finally,
Mix 6 and Mix 13 get a "low" score because their approximated pH is highly variable and may
be too acid for bacterial activity.
176
Speece, Anaerobic Biotechnology for Industrial Wastewaters, 58.
77
Table 30: Score of the Mixes on the Criterion of Suitability Specific to pH
Mix
2. Wasted Activated Sludge and Grease Trap Waste
10. Food Waste, Dewatered Septic Systems Sludge and
Grease Trap Waste
5. Wasted Activated Sludge and Food Processing
Organic
Waste
7. Food Waste and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems Sludge, Poultry
Manure and Grease Trap Waste
14. Food Waste, Dewatered Septic Systems Sludge,
Poultry
Manure, Wasted Activated Sludge and Grease Trap Waste
1. Wasted Activated Sludge and Rinsing Water from
Food
Processing Industry
3. Wasted Activated Sludge, Poultry Manure and
Grease
Trap Waste
4. Wasted Activated Sludge, Dewatered Septic Systems
Sludge and Grease Trap Waste
8. Food Waste and Rinsing Water from Food Processing
Industry
9. Food Waste, Poultry Manure and Grease Trap Waste
12. Food Waste and Food Processing Organic Waste
15. Food Waste, Dewatered Septic Systems Sludge, Poultry
Manure, Wasted Activated Sludge, Grease Trap Waste and
Whey Permeate
6. Wasted Activated Sludge, Grease Trap Waste and Leaves
13. Food Waste, Grease Trap Waste and Leaves
Suitability
(pH)
6.3
6.3
Score
4
6.2
6.2
6.2
3
6.2
6.1
6.1
6.1
6.1
2
6.1
6.1
6.1
5.7-6.4
5.7-6.4
1
Table 31 shows the average score of the mixes on the criterion of suitability. The average score
enables the classification of the combinations by weighting their performance on the C/N ratio
and pH. Mixes 10, 11 and 14 appear to be the most suitable options.
78
Table 31: Average Score of the Mixes on the Criterion of Suitability
Average
Score
Mix
10. Food Waste, Dewatered Septic Systems Sludge and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure and
Grease Trap Waste
14. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure,
Wasted Activated Sludge and Grease Trap Waste
7. Food Waste and Grease Trap Waste
9. Food Waste, Poultry Manure and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure,
Wasted Activated Sludge, Grease Trap Waste and Whey Permeate
8. Food Waste and Rinsing Water from Food Processing Industry
12. Food Waste and Food Processing Organic Waste
2. Wasted Activated Sludge and Grease Trap Waste
3. Wasted Activated Sludge, Poultry Manure and Grease Trap Waste
13. Food Waste, Grease Trap Waste and Leaves
4. Wasted Activated Sludge, Dewatered Septic Systems Sludge and Grease
Trap Waste
5. Wasted Activated Sludge and Food Processing Organic Waste
1. Wasted Activated Sludge and Rinsing Water from Food Processing
Industry
6. Wasted Activated Sludge, Grease Trap Waste and Leaves
2.6.2.2
4.0
3.5
3.0
2.5
2.0
1.5
1.0
Digestibility
Digestibility is defined as the quantity of methane produced during digestion. As covered
previously, it depends on various parameters like temperature and retention time. This analysis is
not intended to predict the exact quantities of methane produced but to rank the different
combinations. Digestibility is considered on a mass basis as well as a time basis. The quantity of
methane produced per ton is useful for scalability purposes. From the perspective that EBI
eventually aims at a larger project, it may be critical to maximize the quantity of methane
produced by mass. Additionally, this metric is not affected by the total quantity of feedstock in
the combinations which varies and tends to give an advantage to the ones with more annual tons.
The total methane production per year is useful to assess the current small-scale project.
Table 32 lists digestibility per mass for all the combinations. As observed, some ranges overlap,
but they are ranked on their potential maximum and minimum. Mix 11 and Mix 10 are judged as
the best ones so they receive an "excellent" score whereas Mix 14 and Mix 15 are ranked right
79
after as "very good". Mix 4 has a small and relatively high range while Mix 12 has a wide range
with a fairly low minimum and a very high maximum; they both obtain a "good" score. Mixes
13, 9, 8 and 7 have a "sufficient" performance because they have a large range with reasonable
maximum values. Finally, the other options, 5, 6, 3, 2 and 1, have small ranges and low values
which justify the "low" grading.
Table 32: Score of the Mixes on the Criterion of Digestibility on a Mass Basis
Mix
11. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure
and Grease Trap Waste
10. Food Waste, Dewatered Septic Systems Sludge and Grease Trap
Waste
14. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure,
Wasted Activated Sludge and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure,
Wasted Activated Sludge, Grease Trap Waste and Whey Permeate
4. Wasted Activated Sludge, Dewatered Septic Systems Sludge and
Grease Trap Waste
12. Food Waste and Food Processing Organic Waste
13. Food Waste, Grease Trap Waste and Leaves
9. Food Waste, Poultry Manure and Grease Trap Waste
8. Food Waste and Rinsing Water from Food Processing Industry
7. Food Waste and Grease Trap Waste
5. Wasted Activated Sludge and Food Processing Organic Waste
6. Wasted Activated Sludge, Grease Trap Waste and Leaves
3. Wasted Activated Sludge, Poultry Manure and Grease Trap Waste
2. Wasted Activated Sludge and Grease Trap Waste
1. Wasted Activated Sludge and Rinsing Water from Food Processing
Industry
80
Digestibility
per Mass
3
(M CH 4/MT)
49-64
4
48-65
Score
47-61
4
46-61
50-52
3
43-62
38-57
36-54
35-54
34-54
25-27
24-27
22-25
20-23
20-22
2
Digestibility on a time basis is used to assess the combinations. Found in Table 33, the ranges are
weighted on their maximum and minimum estimated values. Mix 15 and Mix 14 get a "very
good" score and mixes 4, 11 and 10 are ranked right after with a "good" score. Lower
digestibility is observed for mixes 12, 9, 13, 8 and 7 explaining the "sufficient" grade. Mixes 5,
3, 6, 1 and 2 have a "low" score because they are the options with small ranges at the lower end
of the distribution.
Table 33: Score of the Mixes on the Criterion of Digestibility on a Time Basis
per Time
Digestibility
3
Mix
(x 103 m CH 4/year)
15. Food Waste, Dewatered Septic Systems Sludge,
Poultry Manure, Wasted Activated Sludge, Grease
Trap Waste and Whey Permeate
14. Food Waste, Dewatered Septic Systems Sludge,
Poultry Manure, Wasted Activated Sludge and
Grease Trap Waste
4. Wasted Activated Sludge, Dewatered Septic
Systems Sludge and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems Sludge,
Poultry Manure and Grease Trap Waste
10. Food Waste, Dewatered Septic Systems Sludge
and Grease Trap Waste
12. Food Waste and Food Processing Organic Waste
9. Food Waste, Poultry Manure and Grease Trap
Waste
13. Food Waste, Grease Trap Waste and Leaves
8. Food Waste and Rinsing Water from Food
Processing Industry
7. Food Waste and Grease Trap Waste
5. Wasted Activated Sludge and Food Processing
Organic Waste
3. Wasted Activated Sludge, Poultry Manure and
Grease Trap Waste
6. Wasted Activated Sludge, Grease Trap Waste and
Leaves
1. Wasted Activated Sludge and Rinsing Water from
Food Processing Industry
2. Wasted Activated Sludge and Grease Trap Waste
81
Score
70.0-91.6
4
69.8-91.4
77.2-81.1
68.3-89.9
3
62.9-84.5
46.0-66.8
42.8-64.3
41.5-63.1
2
37.5-58.3
37.4-59.0
32.3-34.7
31.4-34.6
28.6-31.8
26.1-28.5
26.0-29.2
1
Table 34 results from the combination of the two individual analyses of digestibility. An average
score is calculated for each mix. Mixes 10, 11, 14 and 15 are ranked at the top.
Table 34: Average Score of the Mixes on the Criterion of Digestibility
Average
Score
Mix
10. Food Waste, Dewatered Septic Systems Sludge and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure and
Grease Trap Waste
14. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure, Wasted
Activated Sludge and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems Sludge, Poultry Manure, Wasted
Activated Sludge, Grease Trap Waste and Whey Permeate
4. Wasted Activated Sludge, Dewatered Septic Systems Sludge and
Grease
Trap Waste
12. Food Waste and Food Processing Organic Waste
7. Food Waste and Grease Trap Waste
8. Food Waste and Rinsing Water from Food Processing Industry
9. Food Waste, Poultry Manure and Grease Trap Waste
13. Food Waste, Grease Trap Waste and Leaves
5. Wasted Activated Sludge and Food Processing Organic Waste
1. Wasted Activated Sludge and Rinsing Water from Food Processing
Industry
2. Wasted Activated Sludge and Grease Trap Waste10
3. Wasted Activated Sludge, Poultry Manure and Grease Trap Waste
6. Wasted Activated Sludge, Grease Trap Waste and Leaves
82
4.0
3.0
2.5
2.0
2.6.2.3
Inhibitors
The presence of inhibitors may lead to major problems in the anaerobic digester and has the
potential to completely stop bacterial activity. Unfortunately, only limited data related to the
feedstock constituting the mixes are found on this subject. From the current information, poultry
manure and rinsing water from the food processing industry have sulfur and potassium and only
potassium respectively that may be inhibitive at high concentrations. Thus, mixes 3, 9, 11, 14,
15, 1 and 8 which contain one of these two types of waste have a "low" performance score and
the other combinations are judged as "sufficient" because they do not have known probable
inhibitors.
Table 35: Score of the Mixes on the Criterion of Inhibitors
Mix
Inhibitors
2. Wasted Activated Sludge and Grease Trap Waste
4. Wasted Activated Sludge, Dewatered Septic Systems
Sludge and Grease Trap Waste
5. Wasted Activated Sludge and Food Processing
Organic Waste
6. Wasted Activated Sludge, Grease Trap Waste and
Leaves
7. Food Waste and Grease Trap Waste
10. Food Waste, Dewatered Septic Systems Sludge
and Grease Trap Waste
12. Food Waste and Food Processing Organic Waste
13. Food Waste, Grease Trap Waste and Leaves
3. Wasted Activated Sludge, Poultry Manure and
Grease Trap Waste
9. Food Waste, Poultry Manure and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems Sludge,
Poultry Manure and Grease Trap Waste
14. Food Waste, Dewatered Septic Systems Sludge,
Poultry Manure, Wasted Activated Sludge and Grease
Trap Waste
15. Food Waste, Dewatered Septic Systems Sludge,
Poultry Manure, Wasted Activated Sludge, Grease
Trap Waste and Whey Permeate
1. Wasted Activated Sludge and Rinsing Water from
Food Processing Industry
8. Food Waste and Rinsing Water from Food
Processing Industry
83
Score
None known
None known
None known
None known
2
None known
None known
None known
None known
Maybe Sulfur and Potassium (PM)
Maybe Sulfur and Potassium (PM)
Maybe Sulfur and Potassium (PM)
Maybe Sulfur and Potassium (PM)
1
Maybe Sulfur and Potassium (PM)
Maybe Potassium (RWFPI)
Maybe Potassium (RWFPI)
2.6.3
Cumulative Analysis
Following the individual scoring of criteria, a cumulative analysis is required to draw a global
assessment of the options. The criteria before treatment specific to each mix are summarized in
Table 36 and Table 37 and the criteria during treatment can be found in Table 38. These two
tables summarize concisely all the criteria used in the MCA.
Table 36: Summary of the Criteria Before Treatment for the Mixes (1 of 2)
Mix
1. Wasted Activated Sludge and
Rinsing Water from Food
Processing Industry
2. Wasted Activated Sludge and
Grease Trap Waste
3. Wasted Activated Sludge,
Poultry Manure and Grease Trap
Waste
4. Wasted Activated Sludge,
Dewatered Septic Systems
Sludge and Grease Trap Waste
5. Wasted Activated Sludge and
Food Processing Organic Waste
6. Wasted Activated Sludge,
Grease Trap Waste and Leaves
7. Food Waste and Grease Trap
Waste
8. Food Waste and Rinsing
Water from Food Processing
Industry
9. Food Waste, Poultry Manure
and Grease Trap Waste
10. Food Waste, Dewatered
Septic Systems Sludge and
Grease Trap Waste
11. Food Waste, Dewatered
Septic Systems Sludge, Poultry
Manure and Grease Trap Waste
12. Food Waste and Food
Processing Organic Waste
13. Food Waste, Grease Trap
Waste and Leaves
14. Food Waste, Dewatered
Septic Systems Sludge, Poultry
Manure, Wasted Activated
Sludge and Grease Trap Waste
15. Food Waste, Dewatered
Septic Systems Sludge, Poultry
Manure, Wasted Activated
Sludge, Grease Trap Waste and
Whey Permeate
Diversion of waste
Treatment
Fee
($/year)
Transportation
66,375
Diversion from Landfilling (WAS) and
Fertilizing (RWFPI)
Low Reduction
(RWFPI)
67,750
Landfilling (WAS) and Diversion from
Composting (GTW)
Landfilling (WAS) and Diversion from
Composting (GTW)
No Effect
67,300
Landfilling (WAS/DSSS) and Diversion
from Composting (GTW)
No Effect
65,900
Diversion from Landfilling (WAS) and
Composting (FPOW)
Landfilling (WAS) and Diversion from
Composting (GTW/Leaves)
New Treatment (FW) and Diversion from
Composting (GTW)
New Treatment (FW) and Diversion from
Fertilizing (RWFPI)
No Effect
New Treatment (FW) and Diversion from
Composting (GTW)
New Treatment (FW), Diversion from
Landfilling (DSSS) and Composting
(GTW)
New Treatment (FW), Diversion from
Landfilling (DSSS) and Composting
(GTW)
New Treatment (FW) and Diversion from
Composting (FPOW)
New Treatment (FW) and Diversion from
Composting (GTW/Leaves)
New Treatment (FW) and Diversion from
Landfilling (DSSS/WAS) and
Composting (GTW)
High Reduction
(PM)
No effect
77,750
62,275
66,550
65,175
76,550
69,550
79,550
65,175
66,175
84,650
85,600
New Treatment (FW) and Diversion from
Landfilling (DSSS/WAS) and
Composting (GTW)
84
High Reduction
(PM)
No Effect
No effect
Low Reduction
(RWFPI)
High Reduction
(PM)
No Effect
No Effect
High Reduction
(PM)
High Reduction
(PM), Low Increase
(WP)
Table 37: Summary of the Criteria Before Treatment for the Mixes (2 of 2)
Availability
(Seasonality)
All year
Odor
Low
Purity
(Pretreatment)
None
All year with minor
variations (GTW)
All year with minor
variations (GTW)
Mostly Summer for
DSSS and minor
variations over year
(GTW)
All year with minor
variations (FPOW)
Mostly Fall (Leaves)
and minor variations
over year (GTW)
All year with minor
variations over year
(GTW)
All year
Low
None
High
(PM)
Low
None
Low
$30/MT (FPOW)
Low
$37/MT (Leaves)
Low
$20/MT (FW)
Low
$20/MT (FW)
All year with minor
variations over year
(GTW)
Mostly Summer for
DSSS and minor
variations over year
(GTW)
Mostly Summer for
DSSS and minor
variations over year
(GTW)
All year with minor
variations (FPOW)
High
(PM)
$20/MT (FW)
Low
$20/MT (FW)
and $10/MT
(DSSS)
High
(PM)
$20/MT (FW)
and $10/MT
(DSSS)
Low
13. Food Waste, Grease Trap Waste and
Leaves
Mostly Fall (Leaves)
and minor variations
over year (GTW)
Low
$20/MT (FW)
and $30/MT
(FPOW)
$20/MT (FW)
and $37/MT
(Leaves)
14. Food Waste, Dewatered Septic Systems
Maure Wate Acivaed
SlugePoutr
Sludge, Poultry Manure, Wasted Activated
Sludge and Grease Trap Waste
15. Food Waste, Dewatered Septic Systems
Sludge, Poultry Manure, Wasted Activated
Sludge, Grease Trap Waste and Whey
Permeate
Mostly Summer for
DSSS and minor
variations over year
(GTW)
Mostly Summer for
DSSS and minor
variations over year
(GTW)
High
(PM)
$20/MT (FW)
and $ 10/MT
(DSSS)
High
(PM)
$20/MT (FW)
and $1 0/MT
(DSSS)
Mix
1. Wasted Activated Sludge and Rinsing
Water from Food Processing Industry
2. Wasted Activated Sludge and Grease Trap
Waste
3. Wasted Activated Sludge, Poultry Manure
and Grease Trap Waste
4. Wasted Activated Sludge, Dewatered Septic
Systems Sludge and Grease Trap Waste
5. Wasted Activated Sludge and Food
Processing Organic Waste
6. Wasted Activated Sludge, Grease Trap
Waste and Leaves
7. Food Waste and Grease Trap Waste
8. Food Waste and Rinsing Water from Food
Processing Industry
9. Food Waste, Poultry Manure and Grease
Trap Waste
10. Food Waste, Dewatered Septic Systems
Sludge and Grease Trap Waste
11. Food Waste, Dewatered Septic Systems
Sludge, Poultry Manure and Grease Trap
Waste
12. Food Waste and Food Processing Organic
Waste
85
$10/MT (DSSS)
Table 38: Summary of the Criteria During Treatment for the Mixes
Suitability
Mix
Digestibility
(x 103 m 3
CH 4/year)
C/N
Ratio
pH
Dry
Matter
9
6.1
6
20-22
26.1-28.5
9-10
6.3
6
20-23
26.0-29.2
14-15
6.1
7
22-25
31.4-34.6
10-12
6.1
15
50-52
77.2-81.1
9
6.2
6
25-27
32.3-34.7
9-11
5.7-6.4
7
24-27
28.6-31.8
17-18
171
6.2
.
11
34-54
37.4-59.0
17
6.1
10
35-54
37.5-58.3
22-23
6.1
11
36-54
42.8-64.3
10. Food Waste, Dewatered
Septic Systems Sludge and
Grease Trap Waste
17-18
6.3
15
48-65
62.9-84.5
11. Food Waste, Dewatered
Septic Systems Sludge, Poultry
Manure and Grease Trap Waste
21-22
6.2
15
49-64
68.3-89.9
17-18
6.1
11
43-62
46.0-66.8
5.7-6.4
12
38-57
41.5-63.1
20-21
6.2
14
47-61
69.8-91.4
20-21
6.1
14
46-61
70.0-91.6
1. Wasted Activated Sludge
and Rinsing Water from Food
Processing Industry
2. Wasted Activated Sludge
and Grease Trap Waste
3. Wasted Activated Sludge,
Poultry Manure and Grease
Trap Waste
4. Wasted Activated Sludge,
Dewatered Septic Systems
Sludge and Grease Trap Waste
5. Wasted Activated Sludge
and Food Processing Organic
Waste
6. Wasted Activated Sludge,
Grease Trap Waste and Leaves
7. Food Waste and Grease Trap
Waste
8. Food Waste and Rinsing
Water from Food Processing
Industry
9. Food Waste, Poultry Manure
and Grease Trap Waste
12. Food Waste and Food
Processing Organic Waste
13. Food Waste, Grease Trap
WatLeaves
evs18-19
n
Waste and
14. Food Waste, Dewatered
Septic Systems Sludge, Poultry
Manure, Wasted Activated
Sludge and Grease Trap Waste
15. Food Waste, Dewatered
Septic Systems Sludge, Poultry
Manure, Wasted Activated
Sludge, Grease Trap Waste and
Whey Permeate
(i
3
CH 4/MT)
13.-90
86
Inhibitors
Maybe
Potassium
(RWFPI)
None
known
Maybe
Sulfur and
Potassium
(PM)
None
non
None
known
None
known
None
known
Maybe
Potassium
(RWFPI)
Maybe
Sulfur and
Potassium
(PM)
None
known
Maybe
Sulfur and
Potassium
(PM)
None
known
None
knw
known
Maybe
Sulfur and
Potassium
(PM)
Maybe
M a
Sulfur and
Potassium
(PM)
To compare the performance of the mixes on all the parameters, it is necessary to evaluate their
relative importance. Table 39 lists the weight allocated to each criterion previously described.
The levels of importance reflect EBI's objectives with regards to the feedstock. The values are
recommended following discussions with EBI and the prior literature review. The most
important parameter is suitability because it is vital to the entire process. The analysis only
includes suitable mixes, but some of them are more suitable than others. The other very
important criteria are the fee, odor, digestibility and inhibitors. This grading reflects a feedstock
bringing significant revenues with reduced odor and a good behavior in the anaerobic digester.
Availability and purity are evaluated as important because they are not crucial to the success of
the project but they remain reasonably influential. If the feedstock is not available all year, it is
possible to store it and if it is not pure, it may be sorted. These two solutions can potentially be
expensive, but they are resolvable problems. Finally, diversion of waste is considered as
moderately important because it does not have a direct impact on the project.
Table 39: Weight of the Criteria Used in the MCA
Criterion
Bfre
t
Treatment
During
Treatment
Weight
Fee
Diversion of waste
Availability
Oo
3
1
2
Odor
3
Purity
2
Suitability
Digestibility
Inhibitors
4
3
3
Legend
4
3
2
1
Critical
Very important
Important
Moderately important
87
-
55-51.5
Inhibitors
45.5 45.5
.43 42.5
0 Digestibility
40
34 -
35
l Suitability
30
0 Purity
25
H Odor
20
MAvailability
5 Diversion of
waste
E Fee
5
0
14
10
15
11
7
9
2
8 12
Mix
3
4
5
1
13
6
Figure 12: Total Value of the Mixes Based on the MCA
To perform a global MCA and obtain a total value for all the mixes, the score in each criterion is
multiplied by its respective weight to obtain the value of the mix for a given criterion. Then, all
the values are summed to get the total value. The individual values of all the combinations as
well as their total value appear in Figure 12 and detailed scores and values can be found in
Appendix F. Mixes 14, 10, 15 and 11, respectively, obtain the highest total value which greatly
influences recommendations. They are all composed of food waste, grease trap waste and liquid
yeast with variations of poultry manure, dewatered septic systems sludge, wasted activated
sludge and whey permeate.
88
2.7
RISK MANAGEMENT ANALYSIS
Any engineering project involves a certain degree of risk. Indeed, it is important to identify and
analyze these risks in order to face them accordingly. A risk management analysis is pursued
with an emphasis on feedstock. It remains qualitative as the main objective is to recognize the
critical sources of risk that need to be addressed. Initially, the potential strategic issues related to
feedstock management are described which are broad criteria to classify the impacts of risks.
Next, the various stakeholders involved are identified along with the strategic issues they relate
to. Then, the tolerance of the stakeholders regarding each issue is evaluated. Lastly, potential
events involving risk are identified and their criticality is weighted based on the strategic issues.
2.7.1
Strategic Issues
The four major strategic issues of the current analysis are economy, environment, function and
society which are comprehensive but slightly different than the criteria used in the MCA. These
issues enable the identification of the interests of the stakeholders and the risks connected with
each issue. The economic aspect regarding feedstock is related to profitability and costs.
Contamination of the environment and environmental impact are the two subjects associated
with environment where the first is more related to precise events in time and the second issue is
focused on a long-term perspective. The availability of feedstock and its quality are linked to the
functional aspect. Finally, the social criterion is identified as the perception of the project by the
community.
2.7.2
Stakeholders
Various stakeholders are interested in the strategic issues associated with the feedstock. The
main stakeholder is EBI which is the company in charge of the project. The Government of
Quebec and the cities providing organic waste to EBI are two stakeholders from the public
sector. As mentioned previously, the Government of Quebec wants to prohibit landfilling of
organic matter by 2020 which brings this entity in line with the orientation of the project.
Meanwhile, the cities are responsible for the management of their waste and they are clients of
EBI. The other stakeholders are the clients from the institutional, commercial and industrial
sectors.
89
2.7.3
Tolerance Levels
The tolerance level is the level of flexibility a given stakeholder has on a specific strategic issue.
Low tolerance implies that the interested party categorically desires to avoid risks linked to this
issue whereas a stakeholder with high tolerance on a strategic issue may accept certain events.
Table 40 presents the tolerance levels of the stakeholders in regard to each strategic issue. The
following paragraphs describe the strategic issues.
Table 40: Tolerance Levels of the Stakeholders Related to the Strategic Issues
Strategic Issue
Government
of Quebec
Stakeholder
.
Institutional, Commercial
Cities
and Industrial Clients
a.
Profitability
3
3
3
b.
Costs
3
2
2
c.
d.
Contamination
Economic
Environmental
e.
Functional
(Practical)
f.
g.
Environmental
Impact
Quality of
Feedstock
Availability of
Feedstock
Perception by
the community
2
3
3
3
3
3
3
2
2
2
Legend
3
High Tolerance
2
Medium Tolerance
Low Tolerance
No Tolerance
a.
Profitability
For EBI, a main concern is profitability which is translated into a low tolerance towards this
strategic issue. For the project to be sustainable in the long-term, it has to be profitable. The other
stakeholders show a high tolerance because they are not in charge of the project and do not
directly benefit economically from it.
90
b.
Costs
EBI has a low tolerance for the costs because high feedstock costs may compromise the
economic viability of the project. The cities and the commercial, institutional and industrial
clients illustrate a medium tolerance; they have contracts with EBI and high costs may impact
their fee. However, they have the possibility to pursue another treatment for their waste if it
happens to be cheaper. Finally, the Government of Quebec is only indirectly related to the
economics of this specific project which explains its high tolerance.
c.
Contamination
Unanimously, all stakeholders do not tolerate any environmental contamination. It is not in the
benefit of anyone to have a spill or leakage of any sort. Highly organically charged material is
handled and it has to be appropriately contained at all times.
d.
Environmental Impact
The digestion of the feedstock should aim to reduce the environmental impact of the substrate
treated. EBI's mission, to integrate waste management, demonstrates its commitment towards the
environment. Thus, the company has a low tolerance on the environmental impact of the project.
From a broader perspective, the public sector has a high desire to reduce its environmental
footprint and the project may help accordingly. Indeed, the Government of Quebec and the cities
have a low tolerance on this strategic issue. The medium tolerance of the commercial,
institutional and industrial clients is ekplained by the wide range of commitments the companies
have on this strategic issue. Some companies may accept paying a premium to have their organic
wastes diverted from the landfill while some others constantly seek the cheapest option possible.
e.
Quality of Feedstock
The criteria defining the quality of the feedstock are described in the literature review:
suitability, availability, digestibility, purity and inhibitors. Availability of the feedstock is
considered separately because it leads to fairly different tolerance levels and risks. Indeed, EBI
may be highly impacted by the quality of the feedstock; the company is identified with a low
tolerance on this issue. The other stakeholders are considered to have a high tolerance on the
quality of the feedstock because they are not directly impacted by a feedstock with a low quality.
91
f.
Availability of Feedstock
EBI has no tolerance on the availability of organic waste; the lack of feedstock simply
compromises the entire project. A high tolerance is exhibited by the other stakeholders as they
generate the substrate and it is in their interest to make it available to EBI to treat it by anaerobic
digestion which diverts waste from the landfill. However, they are not necessarily bound to this
project and they may seek alternative treatment if it is too difficult to make their organic waste
available to EBI.
Perception by the Community
g.
From EBI's perspective, the project must be perceived positively by the community which
justifies the low tolerance of the company on this issue. The other stakeholders may all benefit
from a positive opinion of the population regarding the project but have less to lose if it turns out
to be viewed negatively.
2.7.4
Sources of Risk and their Criticality
The main sources of risk related to feedstock are listed in Table 41. The criticality of these issues
is identified specifically for each strategic issue. The importance of a given risk is based on the
probability of occurrence and the damages incurred. Thus, a dramatic event with an infinitesimal
possibility of happening may be considered of lesser importance than a risk with a high
likelihood of occurrence and minor damages. An analysis of each source of risk is found in the
following paragraphs.
92
j. High
competition
k. Lower
efficiency of
energy crops
coverage
media
i. Negative
h. Increased
storage costs
1/
1
N/A
N/A
N/A
2
2
______
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2
2
N/A
2
2
2
1
1
N/A
N/A
1
N/A
2
1
2
2
N/A
Environmental
Environmental
Impact
Contamination
2
1
2
1
costs
2
environment
g. Increased
transportation
2
2
Costs
Economic
Profitability
e.Oo .112
emission
f. Spill in the
b. Contaminated
feedstock
c. Feedstock
with low
digestibility
d. Presence of2N/
available
a. Feedstock not
Sources of
Risk (Events)
Strategic Issues
Table 41: Criticality of the Sources of Risk on the Strategic Issues
N/A
N/A
N/A
N/A
N/A
N/A
2
2
Social
N/A
1
2
2
N/A
N/A
2
1
2
1
N/A_2
N/A
1NA
N/A
N/A
1
1
2
g
Perception
by the
community
2
Functional (Practical)
Quality of Availability
of
Feedstock
Feedstock
Medium Risk
Low Risk
Not applicable
2
1
N/A
High Risk
Le end
a.
Feedstock Not Available
Shortage of feedstock implies important consequences for the project in relation to most of the
strategic issues. However, it has a very limited chance of happening; EBI is an established player
in the waste management industry. This event may occur with specific feedstock, but broadly
this risk is judged as medium for profitability, quality of feedstock, availability of feedstock and
perception by the community. Having infrastructure not used to their full potential also slightly
increases the environmental impact of the project. So this event represents a low risk for the
strategic issue of environmental impact.
b.
Contaminated Feedstock
Contaminated feedstock may be considered the most critical event. It is very likely to happen,
especially if food waste is used as input, because it requires pretreatment of the material.
Pretreatment is a proven practice done elsewhere, but it is expensive and avoiding this step
potentially represents benefits. The risk is ranked as high for the strategic issues of profitability,
costs and quality of the feedstock. As pretreatment increases energy usage, this event is
evaluated as a low risk for the environmental impact of the project. Additionally, the availability
of the feedstock can possibly be affected by this source of risk because it can create some
pressure on other pure feedstock resulting in scarcity. Still, this is a low risk in regards to the
availability of the feedstock.
c.
Feedstock with Low Digestibility
A medium risk for profitability, costs and quality of the feedstock is evaluated if EBI attempts to
digest feedstock with low digestibility. With the proper engineering, it is relatively unlikely to
happen, but uncertainties exist in this biological process. Substrate with low digestibility has the
potential to significantly harm the project in the economical and functional aspects. Similarly to
the risk of contaminated feedstock, a low risk is identified in relation to the environmental
impact of the project because the infrastructure would not be used to its full potential. Again, the
low risk for the availability of the feedstock originates from the fact that a shortage of the more
desirable feedstock may be created.
d.
Presence of Inhibitors
Inhibitors are hard to predict and to find in case of occurrence. An event with inhibitors in the
anaerobic digester may compromise the profitability of the project which is a high risk regarding
94
this strategic issue. Moreover, a similar risk is assessed for quality of feedstock because this is
the source of inhibitors. Costs may be incurred to find the reason for inhibition and to prevent it,
explaining the medium risk associated with this strategic issue. The usage of a specific feedstock
may need to cease due to inhibitive concentrations of compounds which is judged as a low risk
for availability of feedstock. The reduced efficiency of the project occasioned by such an event is
a low risk for the environmental impact.
e.
Odor Emission
Odor emission is an event EBI already experienced in the past, and it resulted in terminating the
reception of malodorous waste like poultry manure. The previous attempts to compost this
substrate were done outdoors whereas anaerobic digestion is contained and odor management is
facilitated. Note also that odor propagation is influenced by meteorological conditions which are
out of EBI's control. This source of risk represents a high risk to the perception by the
community because the viability of the project can be compromised. Additionally, odor emission
are a form of environmental contamination and increase the impact of the project on the
environment; the risk is medium regarding these strategic issues. Furthermore, dealing with odor
emissions increases expenses which is a low risk for profitability and costs.
f.
Spill in the Environment
Even if the material handled is mostly organic, a spill in the environment may highly threaten
profitability, contamination in the environment, the environmental impact of the project and the
perception by the community. Meanwhile, large cleanup costs can be engendered. Due to the low
probability of occurrence, this risk is judged as a medium risk for the strategic issues previously
listed.
Increased Transportation Costs
g.
In the event that transportation costs increase, profitability and costs can be negatively impacted.
Still, this source of risk is evaluated as low for these strategic issues because the landfill and
composting platform are located at the same place as the projected anaerobic digester which
means that most of the waste is likely to be transported to EBI's site in any case. Although some
clients may search for nearer places to treat their waste, the targeted feedstock originates from
the same region which reduces this event as a low risk for the availability of the feedstock.
95
h.
Increased Storage Costs
The seasonal variation of most of the feedstock identified in the investigation brings the need for
storage. When possible, outdoor storage is preferable and very cheap. However, feedstocks that
are mostly liquid or that emit odor have to be kept in closed containers where ventilation is
cautiously controlled. This type of storage is more expensive and potential rising costs of this
operation can compromise profitability. The evaluation of this event for profitability and costs
leads to a medium risk because indoor storage is probably needed and costs may increase. This
source of risk is identified as a medium risk for the availability of the feedstock as well; in
addition, seasonal waste may not be available all year due to the costs of storage.
i.
Negative Media Coverage
If negative coverage by the media happens, the perception by the community is the strategic
issue mostly impacted. Some groups or individuals tend to be against waste management
companies in general which makes negative media coverage probable even if the project is
operated responsibly. Still, some of the other sources of risk like a spill in the environment or
odor emissions may lead to legitimate negative media coverage. This event is likely to be the
consequence of the occurrence of other sources of risk. It is judged as a medium risk for the
perception by the community. The risk is considered as low for profitability and availability of
the feedstock because negative media coverage may discourage some clients from treating their
organic waste with anaerobic digestion at EBI. Nonetheless, this probability is of lesser
importance due to the regional location of the clients.
j.
High Competition
Competition already exists in the waste management industry and EBI is used to this dynamic.
The risk of a higher competition in the organic waste industry is probable, especially with the
regulations coming in Quebec in 2020. This event poses a medium risk to the availability of
feedstock explained by clients opting for a potentially cheaper competitor. High competition also
represents a medium risk for profitability because it may force EBI to cut fees, reducing
incomes. Finally, the loss of organic waste to competitors negatively influences costs and quality
of the feedstock, creating scarcity in some types of feedstock or increasing storage requirements.
These impacts are expected to be lesser important so this event is rated as a low risk for these
two strategic issues.
96
k.
Lower Efficiency of Energy Crops
If EBI takes the decision to exploit energy crops there is a risk of lower efficiency than
anticipated. Indeed, depending on the type of crops, the risk is variable but it is a fairly new
activity in a cold climate; significant uncertainties exist. The lower quantities of organic material
impact profitability and availability of the feedstock to a level judged as medium. Other organic
material is treated in the digester and may balance the lack of the energy crops. Having the same
energy spent, but producing less organic material, is also a medium risk for costs. Lower
efficiency of energy crops is a high risk for the environmental impact of the project because
additional energy is used to grow the crops and a lower efficiency may seriously undermine
environmental benefits. A low risk is identified for the perception by the community explained
as a consequence of the increased environmental impact of the project with this event.
The risk management analysis constitutes a strong basis to formulate recommendations which
can be found in the next section.
97
2.8
RECOMMENDATIONS
Numerous recommendations emerge from the current thesis. The literature review, the
investigation and the analysis represent a foundation guiding recommendations. The current
section initially considers the small-scale project EBI targets in the short-term. Next, a global
approach is taken to offer broad recommendations to EBI on anaerobic digestion.
2.8.1
On the Current Project
As stated in EBI's objectives, the company desires to make a controlled investment of less than 1
million dollars in anaerobic digestion. By comparing with similar projects, a reasonable annual
capacity corresponding to this initial investment roughly ranges from 1,000 to 2,000 tons. From
the fifteen feedstock combinations compared in the MCA, many have a relatively high score but
the four mixes shown in Table 42 stand out. They are all formed with a base recipe of food
waste, dewatered septic systems sludge, liquid yeast and grease trap waste. Mixes 11, 14 and 15
include small amounts of other ingredients such as poultry manure, wasted activated sludge and
whey permeate. The annual capacity of these combinations varies from 1,100 tons per year to
1,510 tons per year. The detailed composition of all the mixes as well as the other criteria
evaluated can be found in Appendix E.
98
Table 42: Composition of the Optimal Feedstock Mixes
Type of Feedstock
Mix
Food Waste
10. Food Waste, Dewatered Septic
Systems Sludge and Grease Trap Waste
14. Food Waste, Dewatered Septic
Systems Sludge, Poultry Manure, Wasted
Activated Sludge and Grease Trap Waste
15. Food Waste, Dewatered Septic
Systems Sludge, Poultry Manure, Wasted
Activated Sludge, Grease Trap Waste and
Whey Permeate
1,000
200
Dewatered Septic Systems Sludge
Grease Trap Waste
Liquid Yeast
Total Mix 10
50
50
1,300
Food Waste
1,000
Dewatered Septic Systems Sludge
11. Food Waste, Dewatered Septic
Systems Sludge, Poultry Manure and
Grease Trap Waste
(uty
200
100
Poultr M e
Poultry Manure
Grease Trap Waste
Liquid Yeast
Total Mix 11
50
50
1,400
Food Waste
1,000
Dewatered Septic Systems Sludge
200
Poultry Manure
Wasted Activated Sludge
Grease Trap Waste
100
100
Liquid Yeast
Total Mix 14
50
50
1,500
Food Waste
1,000
Dewatered Septic Systems Sludge
200
Poultry Manure
Wasted Activated Sludge
Grease Trap Waste
Liquid Yeast
100
100
Whey Permeate
Total Mix 15
50
50
10
1,510
Based on the criteria observed and the MCA performed, the mix appearing as optimal is number
14. This combination generates high fees joined with high suitability and digestibility. It
performs well in EBI's key parameters which justifies its selection. The quantity of food waste is
based on pure feedstock; approximately 10% more waste is needed to account for non-organic
material removed during pretreatment so an estimate of 1,100 tons per year of raw food waste is
used.1 77 Nonetheless, Mix 14 has disadvantages worth mentioning. This recommendation is
based on the fact that pretreatment of contaminated food waste may be efficient and
177
Levis et al., "Assessment of the State of Food Waste Treatment in the United States and Canada," 1490.
99
economically viable for EBI. This assumption needs to be tested and validated. In order to
implement this choice, EBI also has to obtain a deal with the company operating the chicken
slaughterhouse to treat some of their poultry manure. As mentioned previously, the facility
annually produces about 8,000 tons and the recommended combination necessitates only 100
tons. In addition to this constraint, the large number of inputs, six, with different delivery
schedules and pretreatment requirements may contribute to complicate operations. Yet, if Mix 14
is too hard to apply in practice, variations of this combination also seem interesting and a simpler
version can reasonably be envisioned if pretreatment of food waste is successful.
Prior to further phases of the project, laboratory testing is essential to properly characterize all
the types of organic waste available to EBI. The data obtained may be used to reformulate mixes
and detect potential inhibitors. Next, additional laboratory experiments where all the
combinations are anaerobically digested are crucial to assess the behavior of the combinations in
a situation close to the real operating conditions. Particular attention should be paid to pH on the
acid end of the desired spectrum. The influence of codigestion on methane production can also
be weighted by laboratory-scale anaerobic digestion. The information obtained can serve to
perform an MCA similar to the one previously done to accurately identify the optimal mixes.
The startup of the anaerobic digester is worth covering. Treatment of the organic waste is done
by a consortium of bacteria but none are present when feedstock is initially inserted in the
digester. According to Gerardi, the startup operation has to be done gradually and may have a
duration of approximately a month for a well-designed treatment unit. Monitoring and control of
pH and alkalinity are very important; pH has to range between 6.8 and 7.2 during that period. It
is also possible, but optional, to seed bacteria in the digester to accelerate the startup. Gerardi
suggests primary wastewater sludge or cow manure that both present strong bacterial assets. This
initiating process is completed when the biogas produced contains an acceptable fraction of
methane and the conditions in the anaerobic digester are stable.178
Once the startup of the facility is finished, a close monitoring of the internal environment is still
necessary. Regular measurements of numerous parameters are useful to understand and control
efficiently the operations: temperature; pH; alkalinity; total solids; volatile solids; C/N ratio; the
evolution of COD during digestion; secondary products like volatile fatty acids, hydrogen and
178 Gerardi, The Microbiology of Anaerobic Digesters, 81-84.
100
ammonia; metals and biogas production and composition. 7 9 Indeed, analyses have a cost, but the
capacity to continuously optimize the anaerobic digester represents a great potential. To
implement such an optimization, a proper framework is needed to understand the internal
environment of the treatment unit and perform adjustments on a continuous basis.
Even if EBI presents a favorable case for energy crops, several reasons justify the
recommendation to avoid this path for the moment. First, energy crops require additional
infrastructure making them less suitable with the company's desire to do a limited investment in
the current project. Second, technological deficiencies need to be improved to ensure reduced
costs and environmental impacts as well as a positive energy balance of the system. Finally, EBI
already has large quantities of organic waste available regionally and should aim toward the
treatment of this material instead of growing new biomass. Managing organic waste is in line
with the company's mission to integrate waste management, and sound from an ethical point of
view.
The current small-scale project is a good way for EBI to verify the concept before investing in
large infrastructure. Experience gained on an anaerobic digester with a limited capacity may
benefit the company and avoid costly mistakes on a major project. Also, the ability to efficiently
perform pretreatment is vital to the project, especially in the case food waste is selected. The
potential risks with a small project are more acceptable for EBI due to the lesser investments at
stake. In this situation, when high-risk events occur, such as contaminated feedstock, presence of
inhibitors or odor emissions, and they are more costly than expected to address, at least the
company goes through a very important learning process. These risks may be mitigated more
efficiently in a larger project when practical experience is obtained from a small-scale facility.
2.8.2
On a Global Perspective
The potential to scale the selected mix is an important element to evaluate. Table 43 compares
the recommended quantity of each feedstock in Mix 14 with the quantity received by EBI in
2013 and potential additional quantities before calculating a scalability factor. This factor is
obtained by dividing the quantity available of a given feedstock by the quantity recommended in
Mix 14. At first sight, the limiting ingredient appears to be liquid yeast with a scalability factor
179 Wellinger, Murphy, and Baxter, The Biogas Handbook, 2013, 231.
101
of 2; this type of feedstock may be added to fulfill micronutrient requirements and Gerardi
recommends a minimum of 1.5 kg/m 3 which is far below the recommended 50 tons per year in a
mix of 1,500 annual tons.180 If the density of water of 1 ton per cubic meter is used to convert the
tons of feedstock to volume, the annual volume is 1,500
M3
which is a conservative assumption
because it overestimates the volume of substrate. Therefore, the minimum quantity stated by
Gerardi for the recommended combination is 2.25 tons of yeast per year which theoretically
brings the scalability factor of liquid yeast to over 44. Dewatered septic systems sludge is the
other feedstock with a low potential for scalability. A lower ratio of this feedstock, or none as in
Mix 9, still appears to be acceptable and might not have a major impact on the treatment. The
same principle applies to grease trap waste and wasted activated sludge which are
complementary; a reduced fraction may be viable. The main limiting type of waste is food waste
with a scalability factor of 12.5. This is the core ingredient in the mix which limits scalability
potential. The quantity of food waste received in 2013 found in Table 45 is on a pure basis which
is estimated to be 90% of the total mass collected.' 8'
Table 43: Evaluation of the Scalability of the Types of Waste in Mix 14
Recommended
Type of Waste
Quantity
(MT/year)
Food Waste
Dewatered Septic
Systems Sludge
Poultry Manure
Quantity
Received in
2013 (MT)
Potential
Quantity
(MT)
Scalability
(QTY Available
/Recommended
QTY)
1,000
11,700
800
12.5
200
1,100
-
5.5
100
100
1,200
Grease Trap Waste
50
500
Liquid Yeast
50
100
Wasted Activated
8,000
-
80.0
12.0
-
10.0
Sludge
2.0
Mix 14 with the maximum quantities available to EBI as of 2013 is shown in Table 44 with the
main parameters of the mix. The different fractions of liquid yeast, dewatered septic systems
sludge and grease trap waste do not seem to affect the global performance of the combination.
The other concerns related to scalability are the large-scale pretreatment of food waste,
Gerardi, The Microbiology of Anaerobic Digesters,
96.
181 Levis et al., "Assessment of the State of Food Waste Treatment in the United States and Canada," 1490.
180
102
homogeneity of the substrate throughout the treatment, and the storage of dewatered septic
systems sludge, grease trap waste and liquid yeast. Nonetheless, the recommended mix appears
to be scalable by a factor of 12.5 if the practical elements raised are addressed.
Table 44: Parameters Calculated for the Scaled Mix 14
Mix
Food Waste
Poultry Manure
Wasted Activated
Sludge
Dewatered Septic
Systems Sludge
Quantity
(TVI/year)
C/N
Ratio
(/N)
Methane Production
3
Dry
DH
Matter
(%)
(X10
(in 3
CHIMi)
M
Fee
3
CH 4 /year)
($/year)
12,500
1,250
18
74
7.5
5.5
10
19
29.4-47.8
53.7
367.5-597.2
67.1
,200
9
7.0
5
15.0
18.0
61,200
1,100
14
7.0
38
127.6
140.4
16,500
Grease Trap Waste
500
10-39
5.0
15
63.2-77.9
Liquid Yeast
100
4
5.7
18
97.2-145.8
31.6-39.0
9.7-14.6
37,500
5,600
16,650
21-22
6.2
12
38.1-52.6
634.3-876.2
995,800
Total Scaled Mix 14
750,000
125,000
To reduce the risks associated with availability, EBI may obtain long-term waste treatment
agreements when possible. Clients from the public sector are bound to public tenders which
typically last for less than five years. Most of the food waste and wasted activated sludge
originates from such entities. Nonetheless, it is possible to sign contracts with private companies
to guarantee reception of feedstock over a longer period of time. It may be particularly
convenient for EBI to bond with the owner of the poultry slaughterhouse. Additionally, the client
providing the liquid yeast has two years left to its contract, so this feedstock needs to be secured.
Grease trap waste and septic systems sludge are both coming from aggregates of numerous
companies and individuals which complicates the situation. The septic systems collection
company owned by EBI, L6veill6 Fosses Septiques, delivers the major fraction of these two
types of waste; this is a recognized company in the regional market and it can rely on a certain
loyalty from its clients. The rest of the grease trap waste and septic systems sludge is delivered
by independent brokers.
As large-scale anaerobic digestion of organic waste is relatively new in Quebec, there may be a
regional first mover advantage for EBI. This waste treatment has a smaller environmental
footprint than landfill and may attract companies concerned by their impact on environment and
their image. However, as mentioned previously, many projects are expected in the near future
103
meaning this competitive advantage might only exist for a few years. Note that only about 20%
of the 4.4 million tons of organic waste generated in the province in 2010 were valorized which
is a market with a tremendous potential for expansion where a large number of treatment
facilities may coexist.1 82 Being a well-known member in the waste management industry in
Quebec, EBI has to lead in innovating practices such as anaerobic digestion and ensure a
strategic position while competition is low.
It is clear that an anaerobic digestion project managed by EBI can have a positive impact on the
regional and provincial waste management landscape especially with the new regulations coming
in Quebec in 2020 prohibiting landfilling of putrescible organic waste.'
83
However, this project
has to be set in a broader perspective; EBI is a corporate citizen of the world, with its rights and
duties like any other entity. The company thrived with a continuous growth over the past decades
and wishes to sustain a responsible development. Such a desire may be fulfilled with an
awareness and leadership in the context of climate change. The planet faces countless global
environmental problems, caused by humans, like global warming, sea level rise,' 4 ocean
acidification' 8 5 and so on. These long-term consequences are mostly caused by massive
combustion of fossil fuels.' 86 Indeed, energy is a necessity for the high consumption lifestyle
adopted in developed countries. As tiny as it may appear, EBI can have a positive impact on a
global scale by establishing more responsible waste management practices regionally. This
anaerobic digestion project is a potential innovation that may set the standards for the future and
contribute to preserving the Earth for generations to come.
182 Recyc-Qu6bec, Bilan 2010-2011 de la gestion des matibres r6siduelles au Qu6bec, 8.
183 Direction des mati&es r6siduelles et des lieux contamin6s, Service des matibres r6siduelles, Banissement des
matibres organiques de 1'elimination au Qu6bec: dtat des lieux et prospectives, VII.
184 Tester, Sustainable Energy, 204.
185 Stephens, "Ocean Acidification,"
1065.
186 Cheng, Biomass to Renewable
Energy Processes., 2.
104
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187
Organic Content
44.2
460
9.6
80
12
4
Carbohydrates,
proteins, lipids
Stomach/intestine
content, pig
150-350
200-500
300-550
250-500
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90
90
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20-25
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35
Wellinger, Murphy, and Baxter, The Biogas Handbook, 2013, 21-22.
(Continuedon next page)
Plant wastes and by-products
Carbohydrates, lipids
Straw
Carbohydrates, lipids
Garden wastes
Carbohydrates, lipids
Grass
Carbohydrates, lipids
Fruit wastes
38.4
400
9.6
80
12
4
Carbohydrates,
proteins, lipids
Stomach/intestine
content, cattle
48.0
300
16.0
80
20
Carbohydrates,
proteins, lipids
12.6
300
4.0
80
5
Poultry manure,
solid
7
Carbohydrates,
proteins, lipids
Poultry droppings
32.0
200
16.0
80
20
Carbohydrates,
proteins, lipids
12.8
200
6.4
80
8
Cattle manure,
solid
13
Carbohydrates,
proteins, lipids
48.0
300
16.0
80
20
Cattle slurry
12.0
Methane
Production
3
3
(M CH 4/m )
300
Methane Yield
3
CH4 /MT VS)
(
4.0
Volatile
Solids
(%)
80
Volatile Solids
(% of Dry
Matter)
5
(%)
Dry
Matter
Carbohydrates,
proteins, lipids
7
C/N
Ratio
Pig manure, solid
Animal Wastes and by-products
Carbohydrates,
Pig slurry
proteins, lipids
Type of
Feedstock
187
APPENDIX A: CHARACTERISTICS OF SOME BIOGAS FEEDSTOCK
Carbohydrates
90
30-50% lipids
90% vegetable oil
40% alcohol
*Fish oil
*Soya oil/margarine
*Alcohol
20
Brewers spent grains
Energy crops
*indicates methane booster
Food remains
10
10
Concentrated
wastewater sludge
5
Wastewater sludge
Sewage sludge
Fodder beet silage
Maize silage
Grass silage
15-40
24
Olive pulp
*Glycerine
98
40
*Bleach clay
17
8.5
95
91
12.6
Thin silage (grain)
80
75
75
90
90
96
40
95
90
90
86
90
1-5
80
90
90
Volatile
Solids (% of
Dry Matter)
Fermentation slop
Whole silage (grain)
7
65-70% lactose,
30-35% lipids
Flotation sludge
5
10
75-80% lactose,
20-25% protein
(%)
Dry
Matter
Concentrated whey
C/
Ratio
5
Organic
Content
Organic wastes from industries
Whey
75-80% lactose,
20-25% protein
Type of Feedstock
(Continuedfrom previous page)
7.5
3.75
18.0
23.0
39.2
38.0
85.5
81.0
7.3
11.5
4.0
9.0
4.5
(%)
Volatile
Solids
500-600
400
400
<450
330
180
800
400
800
800
500
470
350-780
540
540
330
(m
Methane Yield
(ml CH4/MT VS)
30.0
15.0
59.4
41.4
313.6
152.0
684.0
648.0
36.5
53.9
21.6
31.5
15.0
Methane
Production
3
CH 4/m 3)
APPENDIX B: ORGANIC WASTE MANAGED BY EBI IN 2013
Quantities
(Mtyer
Client
Location
Sources
Types
Multiple
Multiple
Septic Systems
Kraft
Montreal
Industrial
Multiple
Multiple
Residential
Metro Beaulieu
Ste-Julienne
Berthierville
Grocery Store
Dewatered
Septic Systems
Sludge
Food Processing
Organic Waste
Food waste
Food waste
Joliette
Sorel-Tracy
Cafeteria
St-Charles-Borromee
Joliette
Joliette
Restaurant
St-Charles-Borromee
Joliette
Restaurant
Berthierville
St-Esprit
Restaurant
St-Felix
Ste-Julienne
Ste-Julienne
Restaurant
St-Jacques
St-Esprit
Cafeteria
St-Hubert
Firestone
St-Hubert
Jardin D'Aphrodite
Annexe
i Rolland
Brulerie du Roy
Rotisserie Benny
Holcim
Rotisserie Benny
Rotisserie Benny
Rotisserie Benny
Camp N-D des Petits
Lemire Fruits et LUgumes
College Esther-Blondin
CPE Bout en Train+OMH
Multiple
Restaurant
Restaurant
Cafeteria
Restaurant
Cafeteria
Restaurant
Cafeteria
Grocery Store
Cafeteria
Multiple
Joliette
Berthierville
(MT/year)
Food waste
Food waste
Food waste
Food waste
Food waste
Food waste
3.3
Food waste
Food waste
Grease trap
1.6
Cafeteria
Grease trap
Ville de Repentigny
Repentigny
City
Centre Nouveau Regard
Notre-Dame-de-Lourdes
Notre-Dame-des-Prairies
Cafeteria
Joliette
Berthierville
Grocery Store
Berthierville
Berthierville
Industrial
Grease
Grease
Grease
Grease
Grease
Grease
Centre Jeunesse
Joliette
Youth Center
COOP Profid'Or
Joliette
Rawdon
Lavaltrie
L'Assomption
Agriculture
IGA
Fromagerie Domaine Feodal
Olymel
Harvey's
CPE Rawdon
Club de Golf Lavaltrie
Ville de L'Assomption
Grocery Store
Cheese
Restaurant
(Continued on next page)
111
14.2
14.2
10.6
4.1
3.3
1.7
1.7
1.6
299.1
64.4
40.8
10.3
18.4
trap
trap
trap
trap
trap
trap
9.3
9.0
Grease trap
Grease trap
Grease trap
4.5
Restaurant
Grease trap
Grease trap
City
Grease trap
Kindergarten
35.4
7.1
Comission Scolaire
IGA
53.1
49.5
42.5
Food waste
Food waste
Food waste
Restaurant
Chez Henri
Restaurant
12,744.7
17.7
St-Charles-Borromee
Rawdon
Club de Golf Berthier
Bakery
251.2
Food waste
Food waste
Food waste
Food waste
Grease trap
Grease trap
Grease trap
Signature & Passion
1,096.0
7.3
7.2
7.1
6.0
4.1
3.6
3.3
2.8
1.5
(Continuedfrom previous page)
Client
Location
Source of
Waste
Multiple
Multiple
Residential
Lawn Clippings
8,398.7
Multiple
Multiple
Residential
Leaves
4,265.9
Fleischmann
Montreal
Industrial
Liquid Yeast
Multiple
Multiple
Sewage
Kraft
Montreal
Industrial
Wasted
Activated Sludge
Whey Permeate
TOTAL
Type of Waste
(Mtyr)
M/er
100.0
1,181.5
2,500.0
31,298.1
112
TOTAL
11,281.0
100
Unknown
Agricultural
Multiple
No
Multiple Farmers
2,500.0
Industrial
Montreal
No
Kraft
100
Poultry Manure
Rinsing Water from
Food Processing
Industry
Straw
Industrial
Berthierville
No
Olymel
2,500.0
Food waste
Grocery Store
St-Michel-des-Saints
Yes
Provigo
39.4
Food waste
Food waste
Food waste
Grocery Store
Restaurant
Grocery Store
Rawdon
Yamachiche
Louiseville
Yes
Yes
Yes
IGA
Porte de la Mauricie
IGA
8,000.0
57.5
56.7
54.6
65
65
65
88.4
87.3
84.0
65
61.1
65
94.0
Restaurant
Yes
100
122.9
73.3
65
65
189.1
112.8
Food waste
Food waste
Food waste
Grocery Store
Grocery Store
Yes
Yes
IGA Crevier
Metro Vercheres
Henri
60.6
130.8
65
201.2
Food waste
Grocery Store
Notre-Dame-desPrairies
Repentigny
Verch&es
St-Charles Borromee
Yes
IGA
8000.0
184.7
65
284.1
Food waste
Grocery Store
Sorel-Tracy
Waste
Quantity
of Organic
Waste
(MT/year)
Estimated
Organic
Fraction
(%)
Initial
Quantity
Q ani
(MT/year)
Yes
Location
Type of Waste
aste
IGA
Managed
by EBI
C: OTHER POTENTIAL ORGANIC WASTE
Client
APPENDIX
Element
(mg/kg)
6.5
25
-
Sludge' 8 8
Wasted
Activated
-
-
350
-
-
-
-
-
waste 9 0
Grease
Geae
trap
114,500
< 0.01
4,770
4,500
-
Wate
Food waste' 8 9
879,450
< 3.3
31,307
7,974
922
4,674
Manure
Poultry
191
Type of Waste
1,573
< 15
22,500
0.2
482
6,930
58
-
Systems
Sludge 9
Dewatered
Septic
Se
s
499,000
5
0.2
22,000
4,000
2,960
-
Organic
Waste 9
Food
Processing
Prgc
PARTIAL CHEMICAL COMPOSITION OF SOME TYPES OF ORGANIC WASTE
Carbon
Cobalt
Iron
Nickel
Nitrogen
Phosphorus
Potassium
Sulfur
D:
188 Perron and H6bert, "Caracterisation des boues d'6puration municipales Partie II : EI6ments traces mdtalliques," 44.
189 Zhao and Ruan, "Biogas Performance from Co-Digestion of Taihu Algae and Kitchen Wastes," 22.; Alkanok, Demirel, and Onay, "Determination of Biogas
Generation Potential as a Renewable Energy Source from Supermarket Wastes," 136-139.
90 Silvestre et al., "Biomass Adaptation over Anaerobic Co-Digestion of Sewage Sludge and Trapped Grease Waste," 6831.
191 EBI's Potential
Client
192 EBI
193 Carucci et al., "Anaerobic Digestion of Food Industry Wastes," 1038.
APPENDIX
2,800
67,750
61,200
51.00
26.0-29.2
18.0
6.3-7.8
4.9-7.3
77.2-81.1
20.0-22.5
15.0
53.7
63.2-77.9
63.2-77.9
97.2-145.8
49.8-52.3
6
5
19
15
18
7
5
38
15
18
15
5.5
1.0
32
100
20
7.4
1.0
1.3
100
20
8.1
6.3
7.0
5.5
5.0
5.7
6.1
7.0
6.9
5.0
5.7
6.1
9
9
74
10-39
4
14-15
9
14
10
4
10-12
1,300
1,200
100
50
50
1,400
1,000
400
100
50
1,550
Wasted Activated Sludge
Poultry Manure
Grease Trap Waste
Liquid Yeast
Total Mix 3
Wasted Activated Sludge
Dewatered Septic
Systems Sludge
Grease Trap Waste
Total Mix 2
56.00
52.12
4.9-7.3
97.2-145.8
18
20
Liquid Yeast
Total Mix 4
75.00
56.00
43.42
7,500
2,800
67,300
6,000
51,000
51.00
15.0
15.0
15.00
2,800
77,750
56.00
55.54
4.9-7.3
31.4-34.6
97.2-145.8
22.4-24.7
51.0
3,750
75.00
127.6
10,000
100.00
5.4
3.2-3.9
3,750
5.7
75.00
5
15
1.0
100
1,200
50
50
Wasted Activated Sludge
Grease Trap Waste
Liquid Yeast
7.0
5.0
6.1
9
1,275
Total Mix 1
9
10-39
4
66,375
61,200
52.06
51.00
26.1-28.5
18.0
3.2-3.9
61,200
2,800
2,375
51.00
56.00
20.4-22.4
15.0
63.2-77.9
4.5
23
25
Processing Industry
(Continued on next page)
Trap Waste
4. Wasted Activated
Sludge, Dewatered
Septic Systems
3. Wasted Activated
Sludge, Poultry
Manure and Grease
Trap Waste
2. Wasted Activated
Sludge and Grease
$/er
95.00
18.0
4.9-7.3
15.0
97.2-145.8
($M)
Fee
($/MT)e ($/year)
3.2
CH 4Iyear)
ethan PrO
Methane Production
(nC4M)
3
6
320
5
18
1.0
20
(%)
Matter
(X 0 7)
7.9
Sludge and Rinsing
9
4
7.0
5.7
C/NDry
pH
(/N)
Ratio
128.3
Rinsing Water from Food
1. Wasted Activated
1,200
50
Quantiy
Quany
(Tya)
15
Wasted Activated Sludge
Liquid Yeast
from Food
WaterWaterfromFood
Processing Industry
Type of Feedstock
Mix
APPENDIX E: DETAILED DESCRIPTION OF THE MIXES
18
4
23
17
1,000
50
25
1,075
1,000
100
50
50
1,200
Food Waste
Liquid Yeast
Rinsing Water from
Food Processing
Industry
Total Mix 8
Food Waste
Poultry Manure
Grease Trap Waste
Liquid Yeast
Total Mix 9
4
22-23
18
74
10-39
4
17-18
50
1,100
Liquid Yeast
Total Mix 7
(Continued on next page)
9. Food Waste,
Poultry Manure
and Grease
Trap Waste
8. Food Waste
and Rinsing
Water from
Food
Processing
Industry
7. Food Waste
and Grease
Trap Waste
4
50
10-39
40
9-11
18
10-39
9
1,100
9
25
25
1,200
1,000
50
6. Wasted
Activated
1,270
5.7
6.1
7.5
5.5
5.0
6.1
4.5
20
7.9
32
100
0.32
8.6
320
18
11
19
15
10
10
15
97.2-145.8
35.7-53.6
53.7
63.2-77.9
29.4-47.8
34.9-54.2
128.3
56.00
63.79
75.00
3.2-3.9
4.9-7.3
42.8-64.3
100.00
60.00
60.63
95.00
5.4
29.4-47.8
37.5-58.3
3.2
2,800
76,550
3,750
10,000
60,000
65,175
2,375
60,000
2,800
60.00
56.00
29.4-47.8
4.9-7.3
29.4-47.8
97.2-145.8
10
18
0.32
20
7.5
5.7
2,800
66,550
56.00
60.50
4.9-7.3
37.4-59.0
97.2-145.8
34.0-53.6
18
11
20
5.7
5.7
6.2
1,875
1,500
62,275
60,000
2,800
56,100
65,900
1,900
3,750
56.00
51.00
51.89
95.00
75.00
60.00
51.90
60.00
75.00
4.9-7.3
16.5
32.3-34.7
9.4
1.6-1.9
5.7-6.1
28.6-31.8
29.4-47.8
3.2-3.9
97.2-145.8
15.0
25.4-27.3
469.8
63.2-77.9
226.8-243.0
23.8-26.5
29.4-47.8
63.2-77.9
18
5
6
15
60
7
10
15
20
1.0
6.7
1.00
13-790
4.1-20
0.32
1.00
5.0
4.1-5.9
5.7-6.4
7.5
5.0
5.7
7.0
6.2
58
4-28
20
320
2,800
56.00
4.9-7.3
97.2-145.8
18
20
5.7
4
50
4.5
61,200
($/year)
51.00
($/MT)
Fee
18.0
Methane Production
CH 4[MT)
(X10 3 M 3
CH 4/year)
15.0
3
5
(x
1.0
Dry
Matter
7.0
[H+]
(x10)
9
C/N
Ratio
pH
(/N)T(%)
1,200
Quantity
(MT/year)
Grease Trap Waste
Leaves
Total Mix 6
Food Waste
Grease Trap Waste
Wasted Activated
Sludge
Liquid Yeast
Trap Waste and
Leaves
Liquid Yeast
Food Processing
Organic Waste
Total Mix 5
Wasted Activated
Sludge
Type of Feedstock
5. Wasted
Activated
Sludge and
Food
Processing
Organic Waste
Mix
(Continuedfrom previous page)
3,750
2,800
69,550
60,000
75.00
56.00
53.50
60.00
3.2-3.9
4.9-7.3
62.9-84.5
29.4-47.8
25.5
63.2-77.9
97.2-145.8
48.4-65.0
29.4-47.8
127.6
15
18
15
10
100
20
5.1
0.32
5.0
5.7
6.3
7.5
6.9
18
14
1,000
60
12
226.8-243.0
37.7-57.4
1,500
66,175
13-790
3.8-22
60.00
60.16
4.1-5.9
5.7-6.4
5.7-6.1
41.5-63.1
40-80
18-19
75.00
1.6-1.9
25
1,100
1,875
56.00
4.9-7.3
97.2-145.8
63.2-77.9
18
15
Leaves
Total Mix 13
60,000
60.00
29.4-47.8
29.4-47.8
10
0.32
20
100
7.5
5.7
5.0
18
4
10-39
1,000
50
25
Food Waste
Liquid Yeast
Grease Trap Waste
2,800
65,175
60.63
2,375
46.0-66.8
95.00
42.8-62.1
11.7
11
469.8
8.6
58
6.1
320
3,750
10,000
17-18
4.5
75.00
1,075
4
100.00
5.4
3.2-3.9
Total Mix 12
(Continued on next page)
Leaves
Waste and
13. Food Waste,
Grease Trap
Organic Waste
Processing
25
2,800
56.00
4.9-7.3
12. Food Waste
and Food
Organic Waste
60,000
60.00
29.4-47.8
29.4-47.8
97.2-145.8
10
18
0.32
20
7.5
5.7
18
4
1,000
50
Food Waste
Liquid Yeast
Food Processing
2,800
79,550
56.00
56.82
4.9-7.3
68.3-89.9
97.2-145.8
48.8-64.2
18
15
20
6.9
5.7
6.2
4
21-22
19
15
53.7
63.2-77.9
50
1,400
32
100
3,000
Liquid Yeast
Total Mix 11
5.5
5.0
15.00
Grease Trap
Waste
74
10-39
38
100
50
1.3
200
ewatered D
11. Food Waste,
Systems Sludge
Poultry Manure
Grease Trap Waste
3,000
Septic Systems
Sludge, Poultry
Manure and
15.00
Food Waste
DwtrdSpi
ewatered Septic
25.5
60,000
60.00
10-39
4
17-18
127.6
29.4-47.8
50
50
1,300
38
1.3
29.4-47.8
Grease Trap Waste
Liquid Yeast
Total Mix 10
7.5
6.9
18
14
($/year)
($/MT)
Sludge and
Grease Trap
Waste
1,000
200
pH
Ratio
(/N)
Systems Sludge
Fee
Septic Systems
10
CH 4/year)
Methane Production
(m CH 4/MT)
(X103 M
Food Waste
Dewatered Septic
0.32
(%)
Dry
Matter
[H+]
(x104)
10. Food Waste,
Dewatered
(M/ea)
C/N
Type of Feedstock
ntity
Qua
Mix
(Continuedfrom previouspage)
00
Dewatered SepticS
Systems Sludge,
Poultry Manure,
Wasted Activated
Sludge, Grease Trap
Waste and Whey
Permeate
14. Food Waste,
Dewatered Septic
Systems Sludge,
Poultry Manure,
Wasted Activated
Sludge and Grease
Trap Waste
Mix
4
17-18
50
1,500
1,000
Food Waste
Poultry Manure
Wasted Activated
Sludge
Grease Trap
Waste
Liquid Yeast
Whey Permeate
Total Mix 15
10-39
50
5.0
5.7
4.5
6.1
74
9
10-39
4
5
21-22
50
50
10
1,510
5.5
7.0
7.5
5.7
6.2
100
100
18
5.5
7.0
74
9
100
100
5.0
6.9
14
200
Dewatered Septic
Systems Sludge
Poultry Manure
Wasted Activated
Sludge
Grease Trap
Waste
Liquid Yeast
Total Mix 14
pH
7.5
C/N
Ratio
18
1,000
Quantity
(MT/year)
Food Waste
Feedstock
Type of
(Continuedfrom previouspage)
[Hi]
3,750
2,800
950
85,600
56.00
95.00
56.69
4.9-7.3
0.1-0.2
70.0-91.6
97.2-145.8
14.9-24.3
46.3-60.7
18
7
14
20
320
8.6
5,100
10,000
75.00
51.00
100.00
60,000
2,800
84,650
3,750
5,100
3.2-3.9
1.5
5.4
60.00
56.00
56.43
75.00
51.00
63.2-77.9
15.0
53.7
29.4-47.8
4.9-7.3
69.8-91.4
3.2-3.9
1.5
15
5
19
29.4-47.8
97.2-145.8
46.5-60.9
18
14
10
63.2-77.9
15
15.0
100
1.0
32
0.32
20
6.6
100
5
1.0
10,000
100.00
5.4
53.7
19
32
3,000
15.00
25.5
127.6
38
60,000
($/year)
60.00
($/MT)
Fee
29.4-47.8
1.3
Methane Production
3 CH4MT)
C 4 e )
29.4-47.8
Dry
Matter
10
0.32
(X10-7)
3
3
2
12
12
2
6
14
16
3.5
14
14
2.5
10
2
2
2
4
2
4
4
8
3
3
2
6
1
3
2
6
2
1
2
2
3
6
3
6
3
6
1.5
2.5
2.5
3
1
1
2.5
2.5
2
2
6
4
12
3
9
2
6
3
9
2
6
Value
Score
Value
Score
Value
Score
Value
Score
Value
Score
Value
7. Food Waste and Grease
Trap Waste
9. Food Waste, Poultry
Manure and Grease Trap
Waste
2. Wasted Activated Sludge
and Grease Trap Waste
(Continued on next page)
3
1
4
3.5
2
1
6
1
1
1.5
1
1
2
1
1
3.5
6
1
3
2
4
6
3
2
1
6
1
6
12
16
4
2
4
3
4
12
16
2
2
3
Score
2
1
3
4
4
1
12
14. Food Waste, Dewatered
Septic Systems Sludge,
Poultry Manure, Wasted
Activated Sludge and Grease
Trap Waste
10. Food Waste, Dewatered
Septic Systems Sludge and
Grease Trap Waste
15. Food Waste, Dewatered
Septic Systems Sludge,
Poultry Manure, Wasted
Activated Sludge, Grease Trap
Waste and Whey Permeate
11. Food Waste, Dewatered
Septic Systems Sludge,
Poultry Manure and Grease
Trap Waste
Value
3
3
4
2
3
1
2
1
1
3
3
4
Inhibitors
Digestibility
Suitability
Purity
Odor
During Treatment
Availability
Criterion
Weight
Score
Fe Diversion
of waste
Before Treatment
F: SCORES AND VALUES OF THE MCA
Mix
APPENDIX
47
47.5
49
50
50.5
51.5
53
TOTAL
VALUE
2
6
1
3
2
6
2
6
1
3
1
3
2
6
1
3
2
8
1.5
6
2.5
10
1
4
6
4
8
1
2
3
6
6
2
6
2
6
2
6
6
4
8
2
4
2
4
2
2.5
2.5
1
1
2
2
6
2
6
2
6
1
3
Value
Score
Value
Score
Value
Score
Value
13. Food Waste, Grease Trap
Waste and Leaves
6. Wasted Activated Sludge,
Grease Trap Waste and
Leaves
6
3
9
2
2
8
3
3
6
2
2
6
3
2
2
2
Score
2.5
1
5. Wasted Activated Sludge
and Food Processing Organic
Waste
1. Wasted Activated Sludge
and Rinsing Water from
Food Processing Industry
6
Value
2.5
3
3
10
8
3
6
3.5
9
Value
2
1
1
2.5
4
1
3
3.5
3
Score
3. Wasted Activated Sludge,
Poultry Manure and Grease
Trap Waste
Score
2
2.5
7.5
3
12
1
2
2
6
3
6
1
1
2
6
Score
Value
12. Food Waste and Food
Processing Organic Waste
4. Wasted Activated Sludge,
Dewatered Septic Systems
Sludge and Grease Trap
Waste
3
6
12
4
6
8
1.5
6
Value
6
1
3
2
3
3
4
Inhibitors
2
2
Digestibility
2
3
Suitability
2
4
Purity
1
1.5
Odor
3
2
Availability
During Treatment
Weight
Score
Diversion
Before Treatment
Criterion
8. Food Waste and Rinsing
Water from Food Processing
Industry
Mix
(Continuedfrom previous page)
34
41
42.5
43
45.5
45.5
46.5
46.5
TOTAL
VALUE