Anaerobic Digestion of Solid Waste
Dorothee Spuhler, seecon gmbh
Anaerobic Digestion of Solid Waste
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Anaerobic Digestion of Solid Waste
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Contents
1. Concept
2. How can Digestion of Green Waste optimise SSWM
3. Design Principals
4. Examples of Applications
5. Applicability
6. Pros’ and Con’s
7. References
Anaerobic Digestion of Solid Waste
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1. Concept
Background
Anaerobic digestion is a natural process which occurs when organic
material is kept in the absence of air. Thereby, the organic material is
transformed into biogas, a renewable and green energy.
In developed countries, this process has been evolved over the past
twenty years, resulting in more and more complex large-scale biogas
plants including heating and multiple stage processes.
So far, several million conventional biogas plants, using predominantly
animal manure as feedstock, have been successfully installed in rural
areas of developing countries. (VOEGELI & ZURBRUEGG 2008)
Anaerobic digestion, as a controlled and voluntary process for the
reduction and reuse of green wastes has a large potential to give
answer to the soaring crisis of increasing municipal solid wastes for
instance in urban and peri-urban areas of the developing world. (VOEGELI &
ZURBRUEGG 2008)
Anaerobic Digestion of Solid Waste
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1. Concept
Anaerobic Digestion of Green Waste (1/2)
Anaerobic Digestion takes place in airtight reactors.
The organic fraction of the wastes is transformed into a mixture of CH4, CO2
and some trace gases (biogas).
The produced biogas can be used either directly for cooking, heating
or lightening
.
It can also be transformed into combined heat and power
cogeneration plants
.
Biogas can also be compressed and sold as fuel
like natural gas.
(CHP) in
(e.g. for vehicles), much
With time the reactors fill up and digested sludge (sludge which organic
fraction was already converted to biogas) accumulates in the bottom.
Nutrients remain in the sludge is a well-balanced fertiliser and can be used in
agriculture
as a rich soil amendment.
Anaerobic Digestion of Solid Waste
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1. Concept
Anaerobic Digestion of Green Waste
Coocking
Green Waste
Biogas
Lightning
Heating
Electricity
Agriculture
Anaerobic Digestion of Solid Waste
Fertiliser
Fuel
D. SPUHLER (2010), Pictures from: www.kristianstad.se/; http://www.newseedadvisors.com/2009/09/10/invest/;
http://www.hydroharrys.com/hydroharrys_about_fertilizer.php; http://www.mytinyplot.co.uk/advice/the-art-of-composting/
www.clker.com [Accessed: 02.06.2010]
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1. Concept
Anaerobic Digestion of Green Waste: Small-scale
Food
Biogas
Energy
Soil amendement
D. SPUHLER (2010). Pictures from: //gardening.ygoy.com/wp-content/uploads/2009/10/how-to-plant-a-decorative-vegetablegarden0.jpg; http://www.gardenplansireland.com/forum/about436.html; http://www.clker.com/ [Accessed: 06.06.2010]
Anaerobic Digestion of Solid Waste
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1. Concept
Anaerobic Digestion of Green Waste: Large-scale
Source: HOLLIGER (2008)
Anaerobic Digestion of Solid Waste
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1. Concept
The example of Kristianstad (Sweden)
Food
production
at farms
Re-use of nutrients
Green waste from
households and
industries
Co-digestion of
waste and
manure
Re-use of energy
Anaerobic Digestion of Solid Waste
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1. Concept
What is Green Waste?
Green waste is any kind refused
material which is biodegradable
and has a high fraction of
organic matter, which can be
transformed into biogas.
Some
examples…
http://www.bawbawshire.vic.gov.au/Page/i
mages/green-waste-grass.jpg [Accessed:
04.06.2010]
Garden refuses
http://www.ducorwaste.org/images/Rally_Time_
Stockpike.jpg [Accessed: 04.06.2010]
http://planetgreen.discovery.com/hom
e-garden/images/2009-04/organicwaste.jpg [Accessed: 04.06.2010]
Waste from
agriculture
Market waste
http://www.agroresources.com/uploads/images
/chocolate%20waste.jpg
[Accessed: 04.06.2010]
Refuses from
the food
industry
http://www.mytinyplot.co.uk/advice/the-art-ofcomposting/ [Accessed: 04.06.2010]
http://www.ceroi.net/reports/dushanbe/eng/waste.htm
[Accessed: 04.06.2010]
Organic fraction of municipal waste
Anaerobic Digestion of Solid Waste
http://www.titech.com/assets/x/50186
?width=82 [Accessed: 04.06.2010]
Some industrial wastes
Kitchen refuses
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1. Concept
What is Biogas ?
Biogas is a mixture of methane and carbon dioxide.
The properties of biogas are similar to the ones of natural gas.
Biogas is the common name for the mixture of gases released from
anaerobic digestion.
Typically biogas is composed of:
Methane (CH4)
Carbon Dioxide (CO2)
Hydrogen (H)
Nitrogen (N2)
Hydrogen sulphide (H2S)
50 to 75 %
25 to 50 %
5 to 10 %
1 to 2 %
Traces
Sources: YADAV & HESSE (1981); FAO (1996); PIPOLI (2005); GTZ (2009
Source: MUENCH (2008)
Methane is the valuable part of the biogas. Biogas that contains about
60 to 70 % of CH4 has a calorific value of about 6 kWh/m3 what
corresponds to about half an L of diesel oil. (ISAT/GTZ 1999, Vol. I)
Anaerobic Digestion of Solid Waste
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1. Concept
What is Anaerobic Digeastion ? (1/2)
Degradation of organic material by bacteria. In the absence of air
(anaerobic). Four stages:
•Hydrolisis
◦ Cleavage of a chemical compound through the reaction with water.
◦ Insoluble complex molecules are bracken down to short sugars, fatty
acids and amino acids.
•Fermentation (Acidogenesis)
◦ Products from hydrolysis are transformed into organic acids, alcohols,
carbon dioxide (CO2), hydrogen (H) and ammonia (NH3).
•Acetogenesis
◦ Organic acids and alcohols are converted into hydrogen (H2), carbon
dioxide (CO2) and acetic acid (CH3COOH). Therefore, oxygen is
consumed and anaerobic conditions are created
•Methanogenesis
◦ Methanogenic bacteria (methanogenesis), transform the acetic acid,
carbon dioxide and hydrogen into biogas.
Anaerobic Digestion of Solid Waste
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1. Concept
What is Anaerobic Digestion ? (2/2)
D. SPUHLER (2010)
Anaerobic Digestion of Solid Waste
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1. Concept
What is a anaerobic digester ?
Source: HOLLIGER
(2008)
1. Airtight chamber, filled with green waste
2. Anaerobic digestion takes place
3. Sludge settles on the bottom
4. Gas bubbles to the top where it is collected
Reaction temperature is > 35 to 55 °C: mesophilic or thermophilic range
Either continuous or in batch mode:
• Batch: filled and left for digestion; After the hydraulic retention time
(HRT) emptied and filled again for a new cycle
• Continuously-stirred tank reactor (CSTR): continuous in/out flow and
mixing
• Plug-flow reactor: the sludge moves through the reactor much like a train
to a tunnel, with a velocity corresponding to the minimal HRT
The liquid phase can be re-circulated to maintain optimal moisture conditions
Anaerobic Digestion of Solid Waste
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1. Concept
Examples: Small-scale digesters
http://www.open2.net/blo
gs/media/blogs/Biogas_pla
nt_Kerala.jpg
Household
floating-drum
digesters
Source: F.
HEEB
Portable
reactors form
the Indian
NGO BIOTECH
http://colli239.fts.educ.msu.edu/wpcontent/uploads/2009/05/biotech2007cc.jpg [Accessed: 04.06.2010]
Anaerobic Digestion of Solid Waste
http://images01.olx.in/ui/4/96/20
/67509620_1-Install-biotechportable-biogas-plants-andconvert-food-waste-to-biogasVazhuthacaud.jpg [Accessed:
04.06.2010]
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1. Concept
Examples: Large-scale digesters
Source: BRUYN (2006)
http://www.klima-sucht-schutz.de/mitmachen/klimaquiz/lexikon.html []Accessed: 04.06.2010
Source: BRUYN (2006)
Anaerobic Digestion of Solid Waste
Source: BRUYN (2006)
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1. Concept
Examples: Biogas Appliances
M. WAFLER
Biogas
cooking
stove
Biogas
boiler
Chang Mai
Biogas lamp
Anaerobic Digestion of Solid Waste
Large
combined
heat and
power
(CHP)
Cogeneratio
n plant
Mini biogas generator
http://www.power.alstom.com/home/new_plants/steam/products/steam_turbines/refe
rences/_files/file_40796_97389.jpg
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2. How the Digestion of Green Waste optimises SSWM
Anaerobic digestion is a
promising answer to the
soaring crises of municipal
waste explosion and thus
prevent the pollution of
water sources and the
evnvironment
Biogas is an renewable energy
and has the potential to
replace other fuel sources.
Biogas contributes to prevent
and lower greenhouse gas
emission.
Coocking
Green Waste
Biogas
Lightning
Heating
Electricity
Agriculture
Fertiliser
Digested sludge can substitute
chemical fertiliser and enhance
food production
Anaerobic Digestion of Solid Waste
Fuel
Sustainable development:
• Improved health
• Improved economy
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3. Design Principals
Basics: Process Parameters
The biogas yield depends on the process and the substrate.
Substrate:
•High COD (Chemical Oxygen Demand) = High potential of biogas generation
Process:
Anaerobic digestion = Biological system of bacteria
Optimal conditions required that bacteria feel wealthy…
•Temperature
◦ Performance
◦ Retention time
•pH
◦ Wide range, but methanogenesis requires neutrality (6.5-7.5)
◦ Multistage process for better pH and temperature control
•Total solid (TS) and moisture
◦ Wet digestion (TS < 20 %): easier to maintain, good fluidity
◦ Dry digestion (TS > 20 %): sophisticated but safes space
Anaerobic Digestion of Solid Waste
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4. Examples of Applications
The ARTI compact biogas plant
Developed in 2003
ARTI = Appropriate Rural Technology Institute
2000 plants currently used in Maharashtra, India (WRAPAI 2009)
Some have been constructed in Tanzania (VOEGELI & LOHRI 2009)
Floating-drum design:
•2 conventional polyethylene tanks (0.75 and 1 m3). (MUELLER
Source: HEEB (2009)
2007)
•Standard plumber piping.
•The smaller tank is the gasholder and the larger holds the
mixture of decomposing feedstock and water
•Inlet and an overflow
•Overflow liquid is mixed with the feedstock and back
recycled into the plant to maintain optimal moisture
condition. (MUELLER 2007)
•A pipe takes the biogas to a collection balloon or directly to
the kitchen.
Anaerobic Digestion of Solid Waste
Source: VOEGELI & LOHRI (2009)
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4. Examples of Applications
The BIOTECH Plant (1/2)
BIOTECH is a nodal agency of the Ministry of Non-Conventional Energy Sources
in Kerala, South India. (MUELLER 2007)
Domestic plants: 1 m3 for a 3 to 5 member-family meets about 50 % of cooking
needs. (MUELLER 2007)
Decentralised treatment of market waste, municipal solid waste or
slaughterhouse waste: Biogas used for public street lightning and distributed
into households
Source: HEEB (2009)
Anaerobic Digestion of Solid Waste
Source: HEEB (2009)
Source: HEEB (2009)
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4. Examples of Applications
The BIOTECH Plant (2/2)
•
•
•
Conventional floating-drum reactor
Liquids are mixed with incoming feedstock and re-circulated
A baffle in the middle increases solids retention
Source: HEEB (2009)
Schematic plan of a BIOTECH market level plant. a) Inlet tank for feedstock. b) Digester tank. c)
Effluent tank. d) Effluent storage tank. e) Effluent pump. f) Gasholder drum. The drum is stabilized
by a guide pole in the middle and is floating in a water jacket outside the digester. g) Biogas pipe. h)
Gas Scrubber. i) Biogas generator j) Drainage connection for excess effluent. (HEEB 2009)
Anaerobic Digestion of Solid Waste
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4. Examples of Applications
The KOMPOGAS Plant
Thermophilic dry digestion
process developed in Switzerland
Organic wastes come from
municipalities with source
separation or from food industry
Horizontal plug-flow reactors
Propellers move the sludge trough
the reactor and keep particles in
suspension. (OSTREM 2004)
Retention time is 20 days. (MES et al. 2003)
Biogas is transformed in a CHP unit providing 100 % of the facility needs as well
as additional electricity for sale. In some cases, the biogas is upgraded to
natural gas standards for use in vehicles or input to the natural gas network.
(OSTREM 2004)
Both liquid and solid effluents are commercialised fertilisers
Anaerobic Digestion of Solid Waste
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4. Examples of Applications
Large-scale Plant in Thailand for Municipal Waste (1/2)
In Thailand, where the development of alternative sources
is critical to energy sustainability as the government has
set 2011 as the target date for 80 % of the nation’s total
energy, representing an estimated 1,900 MW, to be
generated from renewable energy sources. (MUELLER 2007)
This has given large rise to various large-scale biogas
projects.
MUELLER (2007)
The Rayong Municipality has constructed plant for the
treatment of the organic fraction of the municipal
solid waste (MSW) with a capacity of 60 tons of waste
per day.
Two systems:
•Digesters: converts waste to biogas and fertilizer
•A biogas-fired cogeneration process (CHP)
MUELLER (2007)
Anaerobic Digestion of Solid Waste
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4. Examples of Applications
SourcE: MUELLER (2007)
Large-scale Plant in Thailand for Municipal Waste (1/2)
Process: Wet fed-batch high-solids digestion
Feedstock: Organic MSW and refuses from the food industry.
Capacity: 60 tons per day
Output: 5800 tons organic fertilizer and electricity of about 5 million kWh. (MUELLER 2007)
Anaerobic Digestion of Solid Waste
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5. Applicability
Anaerobic digestion can transform almost any biodegradable waste into biogas
(e.g. green waste).
The anaerobic treatment of organic solid waste is applicable everywhere where
there is a need for biogas and waste treatment and the technical conditions
allow the installation of a plant.
Small-scale (biogas generation for cooking and lightening) – low-cost and
relatively low-tech:
• Household-level
• Community-level
• Institutional-level
Large-scale – high-tech, requires expert design:
• Industrial plant connected to the public power and heat grid.
Low-tech (un-heated plants), however, are only adapted to areas where
temperature does not fall short of for any substantial length of time.
Anaerobic Digestion of Solid Waste
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6. Pros’ and Cons’
Advantages:
• Generation of biogas and fertilizer
(almost complete retention of the
fertiliser nutrients (N, P and K)
• Reduction of greenhouse gas
emissions through methane
recovery
• Combined treatment of different
organic waste and wastewaters
• Reduction of solids to be handled
(e.g. less excess sludge)
• Good pathogen removal depending
on temperature
• Process stability (high-loads can be
treated but anaerobic sludge can
also be preserved for prolonged
periods without any feeding)
Anaerobic Digestion of Solid Waste
Disadvantages:
• Small- and middle-scale
anaerobic technology for the
treatment of solid waste in
middle- and low-income
countries is still relatively new
• Experts are required for the
design and construction,
depending on scale may also for
operation and maintenance
• Reuse of produced energy (e.g.
transformation into, fire/light,
heat and power) needs to be
established
• High sensitivity of methanogenic
bacteria to a large number of
chemical compounds
• Sulphurous compounds can lead
to odour
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7. References
BRUYN, J. de, HOUSE, H., RODENBURG, J. (2006): Ontario Large Herd Operators European Anaerobic Digestion Tour Report. Germany, Denmark and the
Netherlands August 21 to 29, 2006. Ontario Ministry of Agriculture, Food and Rural Affairs
FAO (1996): Biogas Technology - A Training Manual for Extension. Consolidated Management Services Nepal (P) Ltd. and Food and Agriculture Organization of
the United Nations (FAO) Available at: http://www.fao.org/docrep/008/ae897e/ae897e00.HTM [Accessed: 19.04.2010]
GTZ (2009): Biogas sanitation for black water or brown water, or excreta treatment and reuse in developing countries. Draft Version.(=Technology review).
Eschborn: German Agency for Technical Cooperation GmbH (GTZ) and Sustainable Sanitation Alliance (SuSanA) Available at:
http://www.gtz.de/en/themen/umwelt-infrastruktur/wasser/9397.htm [Accessed: 11.03.2010]
HEEB, F. (2009): Decentralised anaerobic digestion of market waste. Case study in Thiruvananthapuram, India. Duebendorf: Swiss Federal Institute of Aquatic
Science and Technology (EAWAG). Available at:
http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_swm/downloads_swm/ad_market_waste.pdf [Accessed: 27.04.2010]
HOLLIGER, C. (2008): Microbiologie et Biotechnologie Environnementale. Enseignements au 2iE. Swiss Federal Institute of Technologies (EPFL)
ISAT/GTZ (1999): Biogas Basics. (=Biogas Digest, Volume I). Information and Advisory Services on Appropriate Technology (ISAT) and German Agency for
Technical Cooperation GmbH (GTZ). Available at: http://www2.gtz.de/dokumente/bib/04-5364.pdf [Accessed: 19.04.2010]
MES, T.Z.D. de, STAMS, A.J.M, REITH, J.H., ZEEMAN, G. (2003): Chapter 4. Methane production by anaerobic digestion of wastewater and solid wastes. In:
REITH, J.H., WIJFFELS, R.H., BARTEN, H.(Eds.) (2003): Biomethane and Biohydrogen. Status and perspectives of biological methane and hydrogen production.
Dutch Biological Hydrogen Foundation and the Netherlands Agency for Energy and the Environment (Novem). Available at:
http://gasunie.eldoc.ub.rug.nl/FILES/root/2003/3339875/3339875.pdf [Accessed: 25.04.2010]
MUELLER, C. (2007): Anaerobic Digestion of Biodegradable Solid Waste in Low- and Middle-Income Countries. Swiss Federal Institute of Aquatic Science
(EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC)
http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_swm/downloads_swm/Anaerobic_Digestion_high_resolution.pdf
[Accessed: 27.04.2010]
MUENCH, E. (2008): Overview of anaerobic treatment options for sustainable sanitation systems. In: BGR Symposium „Coupling Sustainable Sanitation and
Groundwater Protection“ 14 – 17 Oct 2008, Hannover, Germany. Eschborn: German Agency for Technical Cooperation (GTZ) GmbH
Available at:
http://www.gtz.de/en/dokumente/en-bgr-conference-biogas-ecosan-muench-2008.pdf [Accessed: 23.04.2010]
OSTREM, K. (2004): Greening Waste: Anaerobic Digestion for treating the organic Fraction of Municipal Solid Wastes. Master theis. Colombia: The Fu
Foundation of School of Engineering and Applied Science, Columbia University
PIPOLI, T. (2005): Feasibility of Biomass-based Fuel Cells for Manned Space Exploration. In: Proceedings of the Seventh Eurpean Space Power Conference,
Stresa, Italy. 9 to 13 May 2005. VOEGELI & LOHRI 2009)
VOEGELI, Y., ZURBRUEGG, C. (2008) Biogas in cities - A New Trend?. In: Sandec News, Vol. 9/2008. Duebendorf: Swiss Federal Institute of Aquatic Science
(EAWAG)
WRAPAI (2009): Document 8, Data Management Document, Appendix S 06 - Energy Research. Australia: Waste Refinery Australia Project Association
Incorporated (WRAPAI) Available at: http://www.members.iinet.net.au/~nwk/wrapai/wr_se8_app_s06_energy.pdf [Accessed: 03.05.2010]
YADAVA, L. S., HESSE, P. R. (1981): The Development and Use of Biogas Technology in Rural Areas of Asia (A Status Report 1981). Improving Soil Fertility
through Organic Recycling. (=Project Field Document No. 10.). Food and Agriculture Organization (FAO) and United Nations Development Programme (UNEP)
Anaerobic Digestion of Solid Waste
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