ALTERNATIVE ELECTRICAL ENERGY SOURCES
FOR MAINE
W.J. Jones
Appendix
M. Ruane
G
CONVERSION OF SOLID WASTES
M. Ruane
Prepared for the Central Maine Power Company.
Report No. MIT-EL 77-010
MIT Energy Laboratory
July 1977
This appendix is one of thirteen volumes; the remaining volumes are as
follows: A. Conversion of Biomass; B. Conservation; C. Geothermal
Energy Conversion; D. Ocean Thermal Energy Conversion; E. Fuel Cells;
F. Solar Energy Conversion; H. Storage of Energy; I. Wave Energy
Conversion; J. Ocean and Riverine Current Energy Conversion; K. Wind
Energy Conversion, and L. Environmental Impacts.
Preface
The Energy Laboratory of the Mass. Inst. of Tech. was retained by
the Central Maine
Power Company to evaluate several technologies
as possible alternatives
(a 600 MWe coal fired
to the construction
generating plant
of Sears Island #1
scheduled for startup in
1986). This is an appendix to Report MIT-EL 77-010 which presents
the results of the study for one of the technologies.
The assessments were made for the Central Maine Power
the basis; that a technology should be:
1) an alternative
to a base-load
power
facility.
generation
electric
Base-load is
defined as ability to furnish up to a rated
capacity output for 6 57 0 hrs. per year.
2) not restricted to a
single
plant.
It
may be several plants within the state of
Maine.
The
combined
output, when viewed
in isolation, must be a separate, "standalone", source of power.
3) available to deliver energy
by 1 985.
Company on
APPENDIX G
CONVERSION OF SOLID WASTES
Page
1.0
2.0
INTRODUCTION
General
1.2
Municipal Solid Wastes (MSW)
1.3
Industrial Solid Wastes
1.4
Agricultural Wastes
1.5
Forestry Wastes
BIOMASS PLANTATIONS - ENVIRONMENTAL IMPACTS
5.0
6.0
G-3
G-3
G-5
G- 5
Physical Characteristics
G-5
2.2
Chemical Characteristics
G-7
2.2.1
Heat Content
G-8
2.2.2
Ultimate Analysis
G-1O
Preprocessing
G-ll
G-14
CONVERSION TECHNOLOGY
Biological Conversion
G-16
3.2
Thermochemical Conversion
G-16
3.3
Direct Burning
G-18
3.4
Comparison of Processes
G-20
3.1
4.0
G-3
2.1
2.3
3.0
G-1
1.1
SUPPLY OF SOLID WASTE IN MAINE
G-21
4.1
Production Rates
G-21
4.2
Population Patterns
G-22
4.3
Energy Potential of MSW
G-25
G-26
ENVIRONMENTAL IMPACTS
5.1
Collection and Transport
G-26
5.2
Conversion Facility
G-28
5.2.1
Incineration
G-28
5.2.2
Refuse-Derived Fuels (RDF)
G-29
G-32
ECONOMICS
6.1
Collection and Transport
G-33
6.2
Conversion Facility
G-35
6.3
6.2.1
Incineration Systems
G-35
6.2.2
RDF Systems
G-36
6.2.3
Dumping Charges
G-37
Discussion
G-37
7.0
CONCLUSIONS
G-39
8.0
REFERENCES
G-41
LIST
OF
TABLES
Page
Table 1.1
Field Crops in Maine
G-4
Table 1.2
Livestock in Maine
G-5
Table 2.1
Composition of MSW (% by weight -as disposed)
G-6
Table 2.2
Projected Composition of MSW (% by weight as disposed)
Table 2.3
G-7
Seasonal Variation of Refuse Composition
Franklin, Ohio
G-7
Table 2.4
Selected Heat Contents for MSW Components
G-8
Table 2.5
Heat Contents of MSW
G-8
Table 2.6
Ultimate Analysis of Typical MSW
G-10
Table 2.7
Analysis of MSW Residue after Incineration
G-ll
Table 3.1
Comparison of Typical Properties of No. 6
Fuel Oil and Pyrolytic Oil
Table 3.2
Comparison of Fluff RDF and Coal
Table 3.3
Comparison of Energy Recovery Efficiencies for
Various Solid Waste Energy Recovery Processes
Table 3.4
G-18
G-19
G-20
Comparison of Energy Recovery Processes
1975 Dollars
G-21
Table 4.1
Sliding Scale of Municipal Waste Generation Rates
G-22
Table 4.2
Population Changes in Maine
G-22
Table 4.3
Estimated 1986 Population and MSW Generation in
Maine
G-23
Table 4.4
Approximate MW Capacity Supportable by MSW
G-25
Table 4.5
Comparison of MSW Transport Modes
G-26
Table 5.1
Emission Factors for Diesel and Gasoline Engines
G-27
Table 5,2
Comparison with Ambient Air Quality Standards for
N.E. Massachusetts Incinerator
Table 5.3
Heavy Metals Present in Leachings from MSW
Residues and Processing
Table 5.4
G-28
Emission Levels During RDF Firing at St. Louis
ii
G-29
G-30
LIST
OF
TABLES
Page
Table 6.1
Transport Cost in Dollars Per Ton Per Mile
G-33
Table 6.2
Incineration Systems Estimated Capital Costs
G-36
Table 6.3
RDF Systems Estimated Capital Costs
G-36
Table 6.4
Hypothetical Utility-Operated Waste-to-Electricity
System Costs Collection System
Table 6.5
Hypothetical Utility-Operated Waste-to-Electricity
System Costs Incineration System
Table 6.6
G-38
Hypothetical Utility Operated Waste-to-Electricity
System Costs RDF System
Table 6.7
G-38
G-39
Hypothetical Utility Operated Waste-to-Electricity
System Costs
G-39
iii
LIST
OF
FIGURES
Page
Figure 1.1
Energy Savings of Recycled Materials - MBtu/ton
G-2
Figure 2.2
Combustion Characteristics of MSW
G-9
Figure 2.3
Typical Pre-Processing Arrangement
G-12
Figure 2.4
Shredding Cost
G-13
Figure 2.5
Shredding Energy
G-14
Figure 3.1
Alternative Energy Conversion Technologies for MSW
G-15
Figure 4.1
Suggested Centroids for MSW Collection
G-24
Figure 5.1
Effect of Volumetric Gas Flow Rate on Particulate
Emissions
Figure 5.2
G-30
Boiler Residue Accumulation Rate for Coal and
Coal-RDF
G-31
Figure 6.1
Transfer Station Investment Versus Capacity
G-34
Figure 6.2
Transfer Station Operating Costs
G-34
Figure 6.3
Transportation Cost for Solid Municipal Waste
G-35
iv
1.0
INTRODUCTION
1.1
General
The United States produces staggering amounts of waste materials,on the order of 160 million
tons peryear by 1980.
The concept of utilizing these wastes is not new, but only in recent years
have the technologies for resource recovery from wastes received wide attention.
This change in
attitude has occurred for three reasons:
·
Traditional disposal methods (landfill, incineration, open dumps, sea dumping, etc.)
have become inadequate for handling the increasing volume of solid wastes in an economical, environmentally acceptable manner.
·
The depletion of inexpensive natural resources has made wastes an
economically at-
tractive source of raw materials.
Solid waste utilization can help maintain adequate energy supplies, both through
energy conservation by the recycling of energy-intensive materials (e.g., glass,
aluminum, iron), and through direct production of fuels and electricity from wastes.
This appendix will not address directly the challenging waste disposal problems facing communities in Maine [see (Colonna and McLaren, 1974) or (EC, 1977)].
Nor will it address directly
the problems and potential of raw material recovery from solid wastes [see (Colonna and McLaren,
1974) or (Blum, 1976, p. 669)].
Instead this appendix will concentrate on the potential
contribution of solid wastes to the electrical energy supply in Maine.
What form might this contribution take?
duction are possible.
Either electricity conservation or electricity pro-
With respect to conservation, it has been estimated thatas much as 200 million Btu/ton
can be saved (Figure 1.1) by recycling aluminum, 12 million Btu/ton for iron and about 2.6 million
Btu/ton for glass [(Kohlhepp, 1975, p. 353) and (Blum, 1976, p. 670)],
materials comprise, respectively,
industrial wastes (see Table 21).
about
On a national basis, these
1%, 9%, and 8% of the total disposed tonnage of non-
However, the potential savings in Maine of nearly 3.5 trillion Btu/yr.
(assuming 3000tons of waste per day by 1986) would not accrue to Maine's electrical energy sector.
This is true for two reasons. Less than 50% of the conserved energy is electrical; coal, oil, and gas
are all utilized, along with electricity, in processing these materials.
Also, the industries which
process aluminum ore, iron ore, and glass are located beyond Maine's borders.
Any electrical savings
would occur in those states as the processing industries used recycled feedstock.
This does not imply that recycling of these materials deserves no further consideration.
The consumers in Maine pay for the energy content of their purchases, and could possibly benefit
their own energy situation by helping relieve unnecessary demands in other parts of the country.
Whether or not a concerted recycling program of energy-intensive materials should be attempted
requires further analysis.
This will not be attempted here since the electrical energy savings
in Maine due to such a recycling effort would be negligible.
This appendix will therefore consider only the production of electricity from wastes.
By
focusing on wastes as a source of energy for electricity production, this appendix takes an unconventional perspective. Research, development, and demonstration efforts reported in the published literature have generally considered the disposal of wastes as the problem of interest.
Energy recovery has been included in disposal system designs because it has offered a means for
reducing the per ton cost of disposal through revenues from the sale of energy.
Hence, the pri-
mary objective of such designs has been the economic disposal of wastes, rather than the economic
production of electricity.
G-1
Figure 1.1
FINISHED
PRODUCT
INGIOT
ORE
-4,BY RECYCLING
Energy Savings of Recycled Materials - MBtu/ton
(Kohlhepp, 1975, p. 353)
Steel
Aluminum
Glass
(Blum, 1976, p. 670)
8.8
12.0
185.0
200.0
2.6
1.2
G-2
Wastes are most easily considered according to their sources:
cultural and forestry.
municipal, industrial, agri-
Nationally the greatest interest has been in the management of municipal
solid wastes (MSW).
1.2
Municipal Solid Wastes (MSW)
Included in the category of municipal solid waste (MSW) are those wastes generated in residences, by commercial activities, and at institutions.
Sewage sludge, abandoned vehicles, demo-
lition and construction debris, and street sweepings are not consideredin MSW. This class of
wastes will be the principal focus of the appendix and will be described in detail in Section 2.0.
1.3
Industrial Solid Wastes
Manufacturing and industrial operations produce wastes which can be considered as either
process or non-process wastes.
Non-process wastes are similar to MSW (e.g., shipping, office,
and cafeteria wastes) and can be found in most industries.
Process wastes are industry-specific
and depend upon the products being manufactured.
On a national basis, industries producing the largest quantities of wastes requiring disposal
are (1) lumber and wood products; (2) printing and publishing; (3) food processing; (4) paper
and allied products; and (5) fabricated metals (Rofe, et al., 1975, p. 41).
industrial process waste producer
In Maine, the largest
is the pulp and paper industry, which also consumes about 75%
of the total energy used in the industrial sector (Page, et al.
industry wastes are generally in the form of bark and sawdust,
1976, p
1-11).
Pulp and paper
The wood products industry is also
a producer of large quantities of waste in the form of shavings, wood scraps, and mill ends.
In Maine,
these wastes have been estimated at 350,000 tons/year (Page, et al., 1976, p. 28) or roughly 3.5 x 1012
Btu/yr (assuming 5,000 Btu/lb).
The industries already use more than 50% of this total resource
for process heat and electricity production [a total of 2.2 x 1012 Btu/yr in 1974 (Page, et al.,
1976, p. 1-12)].
If the remaining wastes were to be used solely for electricity production, they
could provide roughly 19 MW of capacity at 70% load factor.
1.4
Agricultural Wastes
Wastes from field crops and animal husbandry are the two categories of agricultural wastes.
The obstacles to their use as an energy source in Maine are their small total volume and their
dispersed production.
In addition, there are competitive uses for these wastes such as silage
and fertilizer.
Because of the dispersed nature of agricultural wastes, it has been estimated that only about
6% can be considered available for processing to energy (Rofe, et al., 1975, p, 50).
The land
under cultivation in Maine has been decreasing (Table 1.1) but if we assume an average production
of 1 ton of crops per cultivated acre for the 1969 acreage, there would be a total crop production
of about 460,000 tons.
to energy.
We further assume that half of this is wastes and that 6% can be processed
With an average heat content of 5,000 Btu/lb and an efficiency of conversion to elec-
tricity of 25%, there is roughly enough energy for a 1 MW plant.
Of course, this approximation does
not consider the energy, economic, and environmental penalties involved in collecting the wastes.
G-3
Table 1.1
Field Crops in Maine
Item
No. of Farms
Cropland
Corn-silage,
Fodder, Hogged
or Grazed
No. of Farms
Sorghum-Si lage
Fodder, Hogged
or Grazed
No. of Farms
Units
1959
.1964
1969
-
17260
12875
7971
Acres
698188
594434
457935
Acres
8818
-
10048
-
19763
10
1
469
30
Acres
-
-
Hay, excluding
Sorghum
No. of Farms
Acres
451067
-
367476
-
208162
4041
Potatoes
No. of Farms
Acres
-
133349
-
130707
-
152070
2210
Vegetables
No. of Farms
Acres
-
14701
1392
17491
932
13188
644
Berries
No. of Farms
Acres
25212
-
22242
1446
17151
652
Orchards
No. of Farms
*from (USDA,1972, p. 5)
Acres
-
11050
1635
8693
885
7365
383
The dispersed pattern of livestock ownership (Table 1.2) presents problems for the use of
manure as an energy source since
free-roaming livestock.
If we consider 25%
a sizeable fraction of the manure is deposited in pastures by
Poultry appear to be the one exception since most are kept in buildings.
of the total tonnage of dry solids produced to be collectible and assume 6,500
Btu/dry lb and 25% conversion efficiency to electricity, there is potentially enough energy for
roughly a
7 MW plant,
This does not consider the energy, economic, and environmental penalties
involved in collecting and transporting the manures.
G-4
Table 1.2
Livestock in Maine*
Organic Solids (Moisture and Ash Free)**
.
1964
1969
186216
10500
157594
7014
127018
3389
Hogs & Pigs
No. of Farms
24646
4134
13117
1662
7350
609
0.166
1200
Sheep & Lambs
No. of Farms
40615
1627
23381
1008
14332
504
0.084
1200
1.50**
7400
0.0086
175700
Cattle & Calves
No. of Farms
Horses & Ponies
No. of Farms
Chickens older
than 3 months
1.50
4930
1379
7730
3853
4480993
5773
Tons/animal yr
For All Livestock
1959
Stock
4795565
2534
190500
7373553
13057223
459
Broilers less
than 3 months
I
rrr.
I cr .n
IUI#AL
J/OUUU
*from (USDA, 1972, p. 5)
**from (Rofe, 1975, p. 47)
***Estimated by MIT
1.5
Forestry Wastes
In this category are those components of the commercial forest which have no commercial value.
These include the unused tops, branches, stumps, and roots of merchantable trees, trees of noncommercial species, damaged and rotten trees, and brush.
Detailed surveys of the extent of these
wastes are not available and estimates of annual waste production vary by an order of magnitude.
Even so, the most conservative estimates show that forestry wastes could have supplied one-eighth
or more of the total energy needs of Maine in 1975.
Collection logistics are the greatest problem
associated with utilizing forest wastes.
Because of the potentially great energy supply available from forestry wastes, a separate
appendix has been prepared on this energy source (biomass).
The interested reader is referred to
Appendix A (Conversion of Biomass) for more details.
The remainder of this appendix will consider the potential contribution of municipal solid
waste to the production of electricity in Maine.
2.0
MUNICIPAL SOLID WASTE (MSW) AS FUEL
2.1
Physical Characteristics
MSW is the mixed refuse and garbage collected from residences, commercial sources, industrial
non-process sources, and institutions.
The gross composition of MSW is highly variable, changing
from one community to the next, from one truckload to the next, by season and over longer periods
of time (as consumer products change).
The only universal description is that MSW is wet, bulky,
and has an unpleasant odor.
Numerous estimates of the average composition of MSW are available (Table 2.1).
variation seen in Table 2.1
The
reflects some of the difficulties involved in characterizing MSW.
G-5
Of particular importance is the treatment of the moisture content of the wastes, which has been seen
in one study to vary from 3% to 63% around an average of roughly 27% (Klumb, 1976, p. 86).
Mois-
ture content varies primarily as a function of weather and collection practices (e.g., separate
collection of paper and food wastes).
Table 2.1
Composition of MSW (% by weight - as disposed)*
Paper
a
1975-Illinois
I
33.0
Glass
Ferrous Metals
Non-Ferrous Metals
Component
1971-USAb
37.8
38.9
8.0
10.0
n.3
7.6
9.0
-
1.1
Plastics
Leather & Rubber
6.4
Textiles
Wood
Food Wastes
}
15.6
Yard Wastes
Misc. (Ash, Dirt )
1.8
Total Dry Wt.
73.0
Moisture
27.0
TOTAL
100.0
1975-Mlass.d
38.7
0
1
5.9
1.3
3.8
4.1
2.7
2.7
1.6
1.6
3.7
3.6
4.1
14.2
13.3
3.8
14.6
14.1
4.4
1.5
1.5
2.1
included
included
-
-
-
1972-USAe
1972-Kittery,Me
53.0
55.5
9.0
16.1
7.0
}12.9
f
2.7
}2.6
8.0
)12.2
24.0
3.0
73.7
100.0
5.0
Avg. Gen. Rate
lb/person/day
1973-USAC
100.0
3.52
3.32
26.3
included
included
100.0
100.0
100.0
5.5
7.0
4.4
*Moisture migrates from wet to dry wastes during collection; generation rates before collection will
differ slightly from these numbers.
a(Black, 1976, p.63)
b(Lowe, 1974, p. 6)
C(Levy and Rigo, 1976, p. 15)
d(ADL, 1976, p. 12)
e(CEQ, 1975, p. 10-3)
f(Dearborn, et al., 1974, p. 54)
Projected
future comlposition of MSW requires data (or assumptions) on growth rates for each
category of waste (Table 2.2).
Any such projections are conjectural and depend on lifestyle
changes, population growth, and desire for recovery (as a function of economics, technology, and
legislation).
Because the heating value of MSW depends on the relative proportions of combustible
and non-combustible wastes, these changing rates of growth have economic significance for processes
attempting energy recovery from MSW.
The most reliable method for estimating MSW composition in a
region is a survey of existing disposals, preferably over a period of several months (to eliminate
seasonal effects such as those shown in Table 2.3).
G-6
Table 2.2
Projected Composition of MSW
(% by weight - as disposed)
1970
1980
1990
Paper
37.4
40.1
43.4
Glass
9.0
10.2
9.5
Metal
8.9
3.0
8.6
Plastics
8.4
1.4
Leather & Rubber
1.2
1.2
3.9
1.2
Textiles
2.2
2.3
2.7
Component
3.1
2.4
2.0
Food Wastes
20.0
16.1
14.0
Yard Waste
13,9
12.9
12.3
Wood
2.7
3,4
Miscellaneous
2.4
from (ADL, 1976, p. 27)
Table 2.3
Seasonal Variation of Refuse Composition
Franklin, Ohio
Values in Percent
SORT DATES
CATEGORY
4/10-4/18/74
9/17-9/23/74
Paper
33,8
37.34
Inert
2.5
5,18
Glass
9.7
7.94
Metals
10,7
11.88
Non-fiber organics
44.2
37.39
12/16-12/-- /74
49,4
2.4
8.0
10,7
Average
40.1
3.4
8.5
11.1
37.0
29.5
Adapted from (Wittman, et al., 1975, p, 39)
2.2
Chemical Characteristics
Three aspects of the chemical characteristics of MSW are of interest.
The first is heat con-
tent, which will determine the amounts of wastes which must be processed for a given energy output.
The second is the potential for producing objectionable air and water pollution, which will determine the extent of pollution controls needed.
The third is the form of the noncombustible compo-
nents, which will determine the preprocessing and residue disposal required.
G-7
2.2.1
Heat Content
The heat content of MSW is due to the 50-60% of refuse which is combustible (Table 2.4).
Paper products are the largest component of the combustible refuse.
Paper recycling,which can
sometimes be more attractive than disposal, can preclude the use of the remaining MSW as fuel
by removing as much as 70% of the total heat content (CEQ, 1975, p. 10-3).
Moisture can be a significant factor in determining heat content and conversion process efficiency.
Heat content of MSW (HV) is related linearly to moisture content:
HV = Q(1 - M)
(2.1)
HV = heating value (Btu/lb)
Q = dry heating value due to chemical composition
M = moisture content (fraction by weight)
Q varies with composition of the dry MSW, and has been calculated to range between
Btu/lb (Table 2.5).
6000 and 8000
Although Q itself varies due to the changing proportions of combustible and
noncombustible components in MSW, moisture content is more often responsible for changes in total
heat content.
If the moisture fraction, M, exceeds 50%, it is no longer possible to maintain comDepending on the relative proportions of combustible
bustion of MSW without supplementary fuel.
and noncombustible materials in MSW, even moisture contents below 50% will require supplementary
fuels (Figure 2.2)
Table 2.4
Selected Heat Contents for MSW Components*
Component
Btu/lb
Paper
7572
Wood
8613
Grass
7693
Leaves
7096
8850
Leather
Rubber
11330
Plastics
14368
Oils, Paints
13400
8484
Food Wastes
16700
Fats
Metal
124
Glass
65
Ashes
4172
*from (Corey, 1969)
Table 2.5
Heat Contents of MSW
HV (Btu/lb)
M(%)
Q (Btu/lb)
Source
-
6200
20.7
7820
(Corey, 1969)
5200
20
6500
(CEQ, 1975, p. 10-3)
4500
20
6160
(Forrestell, 1976, p. 3), (Lowe,
1974, p. II-9)
4630
28
6430
(Schnelle, 1976, p. 186)
G-8
Figure 2.2
COMBUSTION CHARACTERISTICS OF MSW
10
20
30
40
50
60
70
80
90
% Combustible
Refuse will burn without auxiliary fuel when average composition falls into shaded area.
from (Wheelabrator-Frye, 1976, p. 4)
G-9
Table 2.6
Ultimate Analysis of Typical MSW
Component
% by Weight
% by Weight
as Received
Dry Bases
Moisture
25.1
Carbon
25.2
4.3
3.2
Hydrogen
25.2
18.8
'
Oxygen
33.5
0.4
0.5
0.3
0.4
Sulfur
0.1
0.1
Metal
8.7
11.6
12.2
16.3
6.0
8.1
Nitrogen
Chlorine (organic 40%)
(inorganic 60%)
Glass, Ceramics
Ash
100.0
100.0
Total
from (Rofe, 1975, p. 34)
2.2.2
Ultimate Analysis
Table 2.6 lists the components of typical MSW.
As indicated, MSW has on the order of 0.1%
sulfur, making it an attractive fuel in comparison with coal which ranges from 1% to 4% or more.
Other chemical components tend to remain in the residue or ash produced by energy conversion.
Nitrogen oxide production from bound nitrogen is not a problem,
The moisture component of MSW can
lead to water pollution problems if it is not contained properly.
The residue remaining after the combustible portion of MSW is converted to energy consists
mostly of metals and glass (Table 2.7),
The form of the residue (ash, slag, etc.) depends on the
preprocessing and energy conversion technology employed.
This residue can be used as landfill,
since it is inert, or processed further to recover some of the materials it contains (Blum, 1976,
pp. 671l673).
It is possible that MSW from a particular location may contain substances which when burned
can produce noxious and toxic effluents.
Any operation should include sample monitoring to insure
that such objectionable wastes are not included in the combustion process.
G-10
Table 2.7
Analysis of MSW Residue after Incineration
Component
Analysis (as received percent
by weight)
Iron*
30.5
Nonferrous
2.8
Glass
49.6
Ash
17.1
TOTAL
100.0
*Analysis of magnetic portion picked up and
in iron
Average Weight (%)
02
Carbon
Sulfur
.03
Manganese
.01
Phosphorus
.03
Tin
.17
Copper
.44
Chromium
.09
Nickel
.10
Molybdenum
.02
Lead
.10
TOTAL
1.01
from (Blum, 1976, p. 672).
2.3
Preprocessing
Municipal solid waste contains too great a variety of materials to be used directly for most
energy conversion processes.
Preprocessing of MSW reduces its volume, proces a more uniform size
(which simplifies handling) and removes noncombustible
volume and can cause fouling of equipment).
of recoverable materials.
materials
which increase the residue
Non-combustibles often have value as economic sources
Their recovery is frequently easier before processing for fuel occurs. Pre-
processing usually involves some combination of three operations:
metals recovery, waste classifi-
cation, and waste shredding (Figure 2.3).
Metals recovery operations separate ferrous and non-ferrous metals from the MSW stream.
Bulky
items, e.g., large appliances can be separated manually or by the crane operator as the wastes are
moved in the recovery plant.
The remaining wastes are shredded before further metals recovery since
small, uniform pieces respond better to existing separation processes.
as the waste stream passes an electromagnet.
Ferrous metals are removed
Nonferrous metals are separated on the basis of density
differences (using floatation cells with controlled specific gravity to selectively "float"
off the
metals), eddy currents (induced currents in the metals produce a magnetic field force which results
in the removal of the metals from a conveyor) or electrostatic separation (charged plates hold the
nonmetallic wastes on a rotating drum while metals lose their charge and fall).
Waste classification separates wastes on the basis of size, density, or weight.
Since these
characteristics are roughly correlated to the combustibility of the wastes, classification effectively
separates combustibles and noncombustibles,
A variety of screens or trommels (rotating, cylindrical
screens) separate wastes according to size.
Floatation methods can separate different nonmetallic
G-ll11
Figure 2.3
PRIMARY
SHREDDER
AIR
CLASSIFIER
: SECONDARY
SHREDDER
WASTE
HEAVIES
TROMMEL
TO
LANDFILL
TO
TO ENERGY CONVERSION
MIXED COLOR GLASS
RES
,,
.
_ _.,,
~
TO GLASS COMPANY
Typical Pre-Processing Arrangement
adapted from (Levy and Rigo, 1976, p. 53).
G-12
components in the same manner as the ferrous-nonferrous metals separation was performed.
different specific gravity fluids from before are needed.
For this,
Weight separation relies on air classifiers,
in which the upward flow of air in a cylinder is regulated to force-blow lighter fractions of waste
out the top while heavy pieces fall to the bottom.
Often shredding is performed at several stages.
Initial shredding is used to produce a roughly
uniform size for ease of metal separation and waste classification.
Later shredding depends on
the energy recovery process being used.
Hammermill shredders, in which whirling hammers crush the
wastes, are usually utilized and reduce
MSW to a uniform size which can vary from 8 inches to
0.015 inches in different conversion processes.
The preprocessing of MSW results in an improved input stream to the energy recovery technology
in comparison with the original waste stream.
The combustible fraction nears unity, the heat content
is higher, volume is reduced and handling is simplified.
simplified.
The recovery of reuseable materials is also
This improvement is achieved at the cost of increased investment and energy loss (Figures
2.4 and 2.5).
Preprocessing systems and materials recovery systems are discussed in greater detail
in (Levy and Rigo, 1976, p. 62), (Wilson, 1976), and (Nollet, 1976).
Figure 2.4.
Z
0
FI'
0
U
0U
W
) mm
PRODUCT MEAN $IZ17
Shredding Cost
from (Wilson, 1976)
G-13
Figure 2.5
25
C
0
.C
3
"- 15
IL
CY
UJ: 10
Z
uJ
VI
)
PRODUCT MEAN SIZE
from (Wilson, 1976)
3.0
Shredding Energy
CONVERSION TECHNOLOGIES
Municipal solid waste (MSW) can be converted into a variety of solid, liquid, and gaseous fuels,
Figure 3.1.
Not all of these fuels are suitable for electricity production because of high cost, in-
efficiencies, low heating value, combustion problems, or corrosion problems.
ment of the several conversion methods varies greatly.
The status of develop-
Refuse-to-energy technologies can be
characterized as biological, thermochemical, or direct burning methods (Levy and Rigo, 1976),
(Parkhurst, 1976).
G-14
-
u.C
-
-
FERROIJS
NON-FFERROUS
GLASS
SECONDARY
AvV
(NON-COMB.)
MATERIALS
ETC.
MASS
BURNING
j-
WASTE
SEPARATION
1
V-TJP-'
"'
STREAM" FACILITY
I r.RCA
GENERATE ENERGY
4I1-TANGENTIAL
BURNING
B
MW.
FUEL
LIGHT FRACTION
(COMBUSTIBLE)
ADDITIONAL
HEATING TO
INCREASE BTU.
i.e. ECO-FUEL
-
SECONDARY
PROCESSING
~
-
r~~~~~~~~~~~~~~~
--
-
|
1, -
HYDRO- I CHEMICAL I HYDROI ENATION I REDUCTION] PULPING
tFUL
FUEL
-
UEL
FUEL
PYROLYSIS
FUEL
FUEL
UIL
l
4
BIOLOGICALI OXIDATION
REDUCTION (WET AIR)
FU EL
FUEL
FUE Lt
FUEL
-
.
Figure 3.1
Alternative Energy Conversion Technologies for MSW
from (Schnelle, 1976, p
-
179)
G-15
3.1
Biological Conversion
Biological conversion of MSW produces fuels which have premium uses (e.g., pipeline gas, chemical feedstocks) other than electricity production, although the latter is technically possible (Levy
and Rigo, 1976, p. 56), (Bargman and Betz, 1976).
Commercial operation is considered to be eight
to ten years into the future (Schnelle, 1976, p. 169).
Anaerobic digestion has been in commercial operation for many years as a waste treatment
method in landfills, domestic septic tanks, and municipal sewage treatment.
The process is not
completely understood.
Two classes of bacteria are involved.
molecules into organic acids.
Acidogenic (acid-forming) bacteria break complex organic
These bacteria are hardy and resistant to changes in their environment.
Methanogenic (methane-forming) bacteria feed on the organic acids
dioxide, and water.
to release methane, carbon
These bacteria are easily upset and are slow-growing.
It is not known, for
instance, what effect pesticides and disinfectants in the waste stream would have on these bacteria.
Two methods of obtaining methane by anaerobic digestion are under consideration.
volves drilling into existing landfills and tapping the methane that is produced.
being tested in Los Angeles, California (Mandeville, 1976).
MSW stream in a digestor tank (Klass, 1976).
The second method
The first in-
Prototypes are
uses a preprocessed
Pilot plants are being tested with capacities of 1
to 50 TPD (tons per day).
Enzymatic hydrolysis utilizes a strain of mutant fungus to convert the cellulosic components
of MSW to glucose.
Further processing and fermentation can yield ethyl alcohol (Spans,
process is still in a laboratory stage of development (Andren
3.2
1976).
This
and Nystrom, 1976).
Thermochemical Conversion
Hydrogenation involves breaking the complex organic molecules in MSW and introducing hydrogen
molecules, from steam, into the process.
High temperatures and pressures are needed, and the re-
sulting fuel resembles a heavy fuel oil.
A similar process, hydrogasification, is being considered
for production of methane-rich gas.
Both processes are in the pilot plant stage (Klass, 1976, p. 49)
and are not, at present, serious contenders for electricity production.
Pyrolysis is the most advanced thermochemical system and involves the destructive distillation
of the organic portions of solid waste.
oxygen-poor atmosphere.
Pyrolysis occurs when organic compounds are heated in an
Since it is an endothermic (heat-absorbing) reaction, part of the energy
fuel output must be used to provide the heat for pyrolysis.
Pyrolysis can produce gaseous, liquid,
or solid fuels from MSW, depending on preprocessing, reaction time, temperature, and pressure conditions, catalysts and auxiliary fuels,
Because gas is more versatile than other pyrolysis products,
its production is usually maximized.
At present, four systems are classified as "developmental," i.e., they have been tested in
small pilot plants and currently are being used in full-size plants of 200 tons per day (TPD) which
are in operation or being built.
Several other systems can be considered "experimental" (Levy and
Rigo, 1976, p. 42).
The Monsanto Landgard System pyrolyzes a shredded refuse stream to produce a very low-Btu
3
gas (120 Btu/ft ).
In a 1000-TPD prototype facility in Baltimore, Md., this gas is immediately
burned to produce steam for district heating.
Alternative configurations, such as feeding the hot,
low-Btu gas directly into a utility boiler for electricity production, are possible.
Since the low
heat content of the gas precludes economic shipment over a distance of more than a few hundred yards,
the utility boiler and waste processing facility would have to be right next to each other (Levy
and Rigo, 1976, p. 43).
The Baltimore plant, which was built with an EPA subsidy, has been plagued
with numerous problems since construction was completed in February 1975.
G-16
New air pollution controls
are being installed since the original design failed to meet Federal standards.
The most recent
plant shutdown began in late March 1977 when a conveyor removing slag from the pyrolysis kiln failed.
A 25-day trial run has been the longest period of continuous operation.
The Andco Torrax System does not require preprocessing of MSW and produces a low-Btu gas
similar to that of the Landgard system. This gas also cannot be economically transported, so it
is now burned on-site for process heat and to produce steam. A 75 TPD plant in Erie County, NY
operated intermittently from 1971 to 1974, and a 200 TPD system was to be tested in Luxemburg
beginning in 1976.
No large-scale plants are in commercial operation in the U.S. (Levy and Rigo,
1976, p. 47).
The Union Carbide Purox system (Donegan, 1976) utilizes shredded MSW to produce a medium-Btu
gas (300 Btu/ft3). Unlike the previous processes, which use air, Purox utilizes oxygen to maintain higher temperatures in the pyrolysis reactor.
The higher heat content makes it feasible to
ship the gas several miles, depending on the volume of gas produced and pipeline costs (Schultz,
et al., 1975, p. 79). If this is so, the gas could be sold to utilities or to other gas customers
(Fisher, et al., 1976, p. 459).
A 5 TPD pilot plant was tested in 1970 and a 200 TPD system is in
operation in S. Charlestown, W. Va. The 200-TPD plant is being operated as a research demonstration facility in order to gain design experience for commercial modules in a 200- to 250-TPD
capacity range.
The Occidental Flash Pyrolysis process (formerly the Garrett process) requires extensive preprocessing of MSW and produces an oil-like liquid fuel by condensing a portion of the pyrolysis gases
as they leave the reactor. The remaining gases and residues are used for process heat. The pyrolitic "oil" contains 35% less heat energy (10,500 Btu/lb) than that available in residual No. 6
oil (18,200 Btu/lb), has a higher moisture content, is more acidic and has a higher viscosity (Table
3.1). It also has very low S02 emissions when burned (Blum, 1976, p. 674). A 4 TPD test facility
was operated starting in 1971.
A 200 TPD prototype has been built in San Diego, County, Ca.,
and will produce pyrolitic oil for testing at San Diego Gas and Electric Company power stations.
The cost of construction and a one-year test period has risen from initial estimates of $4 million
to $14.5 million.
The test is subsidized by both EPA and San Diego County. Because of the high
costs,when the test period is completed in May 1978 the county may not be able to keep the plant in
operation (EW, 1977, p. 28).
G-17
Table 3.1
Comparison of Typical Properties of No. 6 Fuel Oil
and Pyrolytic Oil
No. 6
Carbon, weight percent
85.7
Hydrogen
Sulfur
Pyrolytic Oil
57,5
10.5
7.6
0,7 - 3,5
0.1 - 0.3
Chlorine
-
Ash
0.05
Nitrogen
0.3
0.2 - 0.4
0.9
Oxygen
2.0
Btu/pound
33.4
18,200
T0,500
Specific Gravity
0.98
1.30
Lb/gallon
8.18
10,85
148,840
113,900
Btu/gallon
Pour point
F
Flash point
F
Viscosity SSU @ 190F
Pumping temperature
F
Atomization temperature
F
65 - 85
90
150
133
340
1,150
115
160
220
240
from (Mallan and Titlow, 1976, p. 242)
3.3
Direct Burning
This class of conversion technologies includes incineration for steam production and burning MSW
as a supplementary fuel.
Refuse derived fuel (RDF), which can be used for direct burning or as a
feedstock to pyrolysis, is discussed under supplementary fuels.
Waterwall incineration burns either preprocessed or unprocessed MSW in a furnace whose walls
are lined with closely spaced water-filled tubes,
generated heat.
These tubes
remove a major portion of the
Heat recovery boilers in the exhaust gas stream remove additional heat and so re-
duce gas volume before the exhaust enters the plant pollution control equipment.
Such furnaces
have been used widely in Europe for over 20 years, where landfill opportunities, fuel costs, and
institutional factors have long combined to make steam recovery attractive.
European systems are
typically low-temperature, low-pressure systems while most U.S. utilities operate high-temperature
and pressure units.
As a result, corrosion is not a serious problem in Europe (Lawrence, 1976, p. 349).
In this country, a number of systems using unprocessed MSW have been operating for several
years.
The U.S. Naval Station, Norfolk, Va. has operated a 360 TPD plant since 1967, supplying
the base's heating and cooling needs.
Chicago, Ill, (1600 TPD), Saugus, Mass.(Forestell, 1976),
(1200 TPD), and Harrisburg, Pa., (720 TPD) have facilities which have operated successfully for
several years, although steam sales have not been consistent due to a lack of customers.
1976, Table II).
(Parkhurst,
An installation in Nashville, Tenn., (720 TPD), has operated since 1975 supplying
heating and cooling to downtown buildings.
Many of these facilities have had air pollution problems from particulates.
Recent installations
have generally operated reliably and economically, especially when the steam customers were identified beforehand.
Electric utilities could use the steam for electricity but backup systems to
G-18
ensure a constant supply would be required (Levy and Rigo, 1976, p. 28).
There has been less operating experience here and abroad with waterwall incineration of processed
wastes.
Plants are announced or under study in Akron, Ohio, (1000 TPD), Niagara Falls, NY, Hempstead,.
NY, (200 TPD), and Dade County, Fla (3000 TPD).
A fluidized bed incinerator of MSW which uses a gas turbine in order to generate electricity,
has been tested in Menlo Park, Calif., in a 100-TPD pilot plant.
This system has not yet performed
well enough to warrant building a prototype plant (Black, 1976, p. 30), (Huffman, 1976, p. 402).
Supplementary firing of refuse involves preprocessing of MSW to remove metals and other noncombustibles.
MSW would foul
Further processing produces a homogeneous refuse-derived fuel, (RDF).
Unprocessed
and corrode conventional boilers if used as a supplementary fuel.
RDF is pneumatically fed into a conventional boiler where it burns in suspension with normal
fossil fuels.
The degree of shredding (or further processing) depends on the design of the fossil-
fired boiler, since it is more practical to produce an RDF which is compatible with the present fuel
system than it is to modify significantly the combustion systems.
RDF are being offered:
As a result, several types of
fluff RDF, densified RDF, and dust RDF.
Fluff RDF can be produced by both dry and wet processing systems.
In the dry systems, the
combustible waste stream from the preprocessing facility is shredded to a size which will burn
readily in suspension (Table 3.2).
Such a system-was successfully tested by the EPA
and Union Electric (on a pilot plant scale) in St. Louis, Mo.,
from 1972 to 1975.
MSW was collected
from St. Louis at a central processing plant and the RDF was then shipped to the utility boilers
where it was burned with coal (Lowe, 1973).
RDF constituted up to 28% of the heat input.
Subsequent attempts to establish a permanent full-scale system in St. Louis have failed due to
public opposition to transfer stations for the MSW.
Electric Light and Power, 1977, p. 2).
fluff RDF plants are in operation or planned for Ames, Ia.,
Other
(200 TPD) (ELP, 1976), (Funk and
Sheahan, 1976), Bridgeport, Conn., (1550 TPD) (Mallon and Titlow, 1976, p. 248), Milwaukee, Wis.,
(Lawler, 1976), and Chicago, Ill. (200 TPD) (Suloway, 1976, p. 437).
Table 3.2
COMPARISON OF FLUFF RDF AND COAL
.
Per Pound
Fluff RDF
Coal
Property
5,000 - 6,500
HeatingValue (Btu/lb)
Bulk Density (Lb/Ft3)
Moisture
AverageSize (In.)
5-9
20 - 30%
106
11,500- 14,300
106
42
3-12%
31 - 60 Lb
Lb
Lb
3-11
29- 38
43- 56
2-10
2- 10 Lb
1/4-2
19.
28.
6.9
0.6
45.
0.2
Ash
Carbon
Hydrogen
Nitrogen
Oxygen
Sulfur
.
Per MillionBtu
Fluff RDF
Coal
6.2 - 81
4.3- 6.0
1.0- 1.7
4.8 - 17.4
0.6 - 4.3
11 -14
.9 - 1.2
64 - 90
2.5 - .35
43 - 70
3 -5
.7 -1.5
15
.4-3.7
.
.
.
from (Levy and Rigo, 1976, p. 35)
G-19
.
Wet process fluff RDF uses hydropulper technology (from the paper industry) to separate the
waste stream into combustible and noncombustible components and to reduce the combustibles to an
aqueous slurry. This fraction can then be dewatered to any desired moisture content.
Wet proces-
sing is advantageous when sewage sludge must be treated, but the dewatering process can be prohibitively expensive.
A demonstration plant by Black-Clawson in Franklin,
. (150 TPD capacity -
45 TPD operation) has operated since 1971 (Whittman, 1975), but no commercial installations are planned.
Densified RDF is produced by pelletizing, briquetting, or extruding fluff RDF, or by binding
dust RDF into briquettes.
Small quantities have been produced and burned successfully, but the
process is not yet near commercial status (Levy and Rigo, 1976, p. 40).
Dust RDF can be fired along with coal or may even be slurried with oil.
Coarse, shredded
MSW is embrittled and shattered to form particles of dust RDF of about 0.006 inches.
developed by Combustion Equipment Associates under the name Eco-Fuel II
This process,
(ADL, 1976), was used for
21 months in a 4 TPD pilot facility . A 480 TPD facility in East Bridgewater, Mass., will produce
dust RDF for use in industrial process steam boilers,
is also planned (Rofe, et al., 1975, p. 72).
An 1800 TPD facility in New Britain, Conn.,
Dust RDF has superior combustion and handling pro-
perties when compared to fluff RDF,
3.4
Comparison of Processes
The choice of the best conversion process for electricity production is a complex decision.
It
must include consideration of the entire waste collection and treatment process, not just energy
recovery.
The choice is necessarily site-specific, and considering that most processes lack exten-
sive commercial experience, somewhat risky.
unavailable for most processes.
Conversion efficiencies of MSW to electricity were
However, comparative efficiencies to steam production were found
(Table 3.3).
Table 3.3
Comparison of Energy Recovery Efficiencies
for Various Solid Waste Energy Recovery Processes
Process
Net Fuel Produced
Total Amount Available
as Steam
(Expressed as percent of heat value of incoming
solid waste)
Water Wall Combustion
Total Available as
Electricity
- %
(35% turbine
efficiency)
(MIT)
59
.21
Fluff RDF
70
49
17
Dust RDF
80
63
22
Wet RDF
76
48
17
Purox Gasifier
64
58
20
Monsanto Gasifier
78
42
15
Torrax Gasifier
84
58
20
Oxy Pyrolysis (Garrett)
26
23
08
29
42
15
14
05
Biological Gasification*
With use of residue
Without
16
se of residue
Brayton Cycle/Combined Cycle
19 plus
19
Waste Ffred Gas Turbine
12 directly
as electricity
12
*Tn~llrl
p
nrnr
frm11.
1 UC(L euvv IICl
. d
frnm
rnrnrmA
y
Ruguy,.
from (Levy and Rigo,
l
cpwanp
Inv
cIllnP
I
1976, p. 23).
G-20
The last column of Table 3.3 illustrates total efficiencies of electricity production assuming
bine efficiencies of 35%.
tur-
Actual turbine efficiencies are process-dependent and might produce
slightly different numbers.
The rapidly changing status of many of these technologies makes comparisons of future performance and costs hazardous.
One comparison for large systems, as of 1975, is given in Table 3.4.
Table 3.4
Comparison of Energy Recovery Processes
1975 Dollars
:E:
mrn
I D
m--I
-m
i-- ;
30
1n1 0I
I C)
OW
C) c
o
D r0':
O
I C
-H
C)
0
1
co
0
-< rl
- O
-
wra
HO
= C)
rr'I --A
--I-n
4IV
-oc
Z
m.z
--
00
XZ
;O
;; --I
0
0 2
)
-10
0
;C
-I
V)
-
CDA
00
C)
-< --
-ow
C)
0
Investment
($/Daily Ton)
31,000
OC
;c
Qo
m
A
·I
C)
.C
c no
C)
o
O
3Z
11,100
18,000
13,500
22,5000
C)
C)
P1
'-4rm ;:
:ZC
P1
o
COw
.o
Costs
m
x-
D
C)-o
P1C
I
C)
D
c
2 0
* m
20,000
21,000
22,000
15,000
18,200
Total Operating
Cost ($/Ton)
11.71
6.76
8.88
8.12
9.21
10.55
11.75
10.07
9.10
14.31
Capital Costs
10.3
3.68
5.98
4.49
7.48
6.55
6.98
7.31
4.99
6.05
12.00
6.80
9.00
5.16
5.50
9.60
7.00
13.50
6.30
7.14
1.68
1.67
1.68
3.50
3.65
2.05
3.69
2.05
0.60
1.68
Credits
Energy Credits
Materials
Credits
Sewage Sludge
Disposal
1.88
Net Amortized
Operating Cost
8.33
1.97
4.18
3.95
7.54
5.55
8.04
1.83
7.19
9.66
Energy Recovery
Efficiency
67%
66%
62%
57%
36%
42%
36%
65%
32%
25%
from (Schultz, et al., 1975, p. 10)
4.0
SUPPLY OF SOLID WASTE IN MAINE
4.1
Production Rates
Table 2.1 compiled several recent estimates of waste generation rates.
to 7.00 lb/person/day.
These ranged from 3.32
Two local surveys of waste production arrived at a 1976 rate
of 4.25
lb/person/day in the Waterville area and a 1975 rate of 3.78 lb/person/day in the Auburn area
(Beaulieu, 1976), (ADL, 1975, p. 1-2), (Stephens, 1976, p. 387).
A sliding scale has also been used
to reflect the decreased waste generation rates found in rural areas (Table 4.1).
A state average
of roughly 4.2 lb/person/day was estimated (Dearborn, et al., 1974, p. 54) using a 1974 population
of 1.047 million (U.S. Bureau of Census, 1975).
G-21
Table 4.1
Sliding Scale of Municipal Waste Generation Rates
Population Municipality
Lb/person/day
< 1,000
2.2
> 1,000
2.5
> 5,000
3.5
> 10,000
4.5
from (Dearborn, et al., 1974, p. 20)
Determination of future generation rates in Maine is a matter of conjecture.
For example, the
trend of increased packaging of consumer goods could be offset by state or federal legislation.
One study suggested that per capita rates wouldactually decrease (from 3.78 to 3.48 lb/person/day)
(ADL, 1975, p. I-2).
Since we are concerned with assessing the ultimate energy potential of munici-
pal solid waste (MSW), let us assume that 1976 urban and rural generation rates averaged 4.0 lb/
person/day and are growing at 2% per year. In 1986, the generation rate will be 4.9 lb/person/day.
4.2
Population Patterns
Maine's population grew 5.3% from the 1970 census to 1974 (Table 4.2).
annual rate of growth of 1.3% (U.S. Bureau of the Census, 1975).
This represents an
Assuming that this rate continues,
the 1986 population of Maine will be 1.225 million.
Table 4.2
Population Changes in Maine
Population
April 1, 1970
993,663
July 1, 1974
1,047,000
1970
Births
71,000
to
Deaths
46,000
Migration
28,000
1974
from (U.S. Bureau of the Census, 1975).
Two qualitative aspects of population patterns affect MSW production.
industry.
The first is the tourist
Maine's summer population is bolstered by an influx of visitors, with a resulting increase
in business activity and MSW production.
This increase, which is a function of weather, the
state of the economy and location in Maine is superimposed on the normal seasonal variation of MSW
generation due to yard wastes, etc.
MSW production in Maine.
more rural lifestyles.
No survey data were found on this seasonal component of
The second aspect of interest in Maine's population is a trend towards
Although census data are not yet available to quantify this trend, it
appears that new household formation is occurring more often in smaller towns than in urbanized
areas in Maine.
If this is so, it could have implications for the rates of MSW production since
in the past rural lifestyles have generated less collectible MSW than urban living.
There will cer-
tainly be cost and energy penalties in the collection of MSW from a dispersed population.
We will have to ignore the quantitative impacts of these trends until data become available,
but their potential effects would need investigation before any specific plans for energy from MSW
were implemented.
G-22
Population in Maine tends to concentrate in the southern third of the state.
have been suggested as centroids for MSW collection (Figure 4.1).
80% of Maine's population.
Fourteen regions
These 14 regions contain roughly
The first five regions alone contain roughly 40% of the total (Table 4.3).
Figure 4.1
SUGGESTED CENTROIDS FOR MSW COLLECTION
G-23
Table 4.3
Centroid
Estimated 1986 Population and MSW Generation in Maine
Estimated
Estimated
Population 1986**
Name
Population 1976*
MSW, TPD 1986
-
-
1
Portland
204,000
232,000
569
2
Bangor
102,000
116,000
323
3
Augusta-Winslow
98,000
112,000
312
4
Lewiston
95,000
108,000
301
5
Sanford-N. Berwick
67,000
76,000
212
6
Brunswick
55,000
63,000
176
7
Rockport-Warren
40,000
46,000
128
8
Ellsworth City
30,000
34,000
95
9
Norway
24,000
27,000
75
72
10
Belfast City
23,000
26,000
11
Rumford
22,000
25,000
70
12
Newport
21,000
24,000
67
64
45
13
Farmington
20,000
23,000
14
Dover-Foxcraft
14,000
16,000
* derived from (Bagley, 1977)
** assumes population growth at 1.3%/yr.
G-24
4.3
Energy Potential of MSW
In Table 3.3 we saw that efficiencies for converting MSW to electricity ranged from 8% to 22%.
The most thoroughly proven technology for direct use of MSW was waterwall incineration with an efficiency of 21%.
Dust RDF, which would be burned as a supplementary fuel in existing boilers, could
In Section 2.2 we saw that the heat content of
produce electricity with roughly 22% efficiency.
raw MSW varies from 4!500to 6200 Btu/lb, .
If we optimistically assume a heat content of 6200 Btu/lb, with waterwall incineration, and
with 24-hour/day firing of refuse fuel, the MSW of the entire state of Maine in 1986 could produce
the energy equivalent of a 95 MW generating plant (100% load factor).
In practice, many problems
would tend to reduce the actual energy available.
Because the wastes are so dispersed, a single waterwall incineration facility would be impractical.
The alternatives are to construct several incinerators close to the MSW sources or to con-
struct RDF conversion plants and ship the fuel to one or more boiler facilities.
Logistical and
institutional problems with the collection of raw MSW from the public make it likely that at least
one incinerator, RDF conversion plant, or waste transfer station would be required in each of the
centroids of Figure 4.1.
The energy potential of each centroid, expressed in MW capacity for 24-hour/day
firing of raw MSW or RDF, is given in Table 4.4.
Table 4.4
Approximate MW Capacity Supportable by MSW
Centroid
MW
1.
Portland
18
8.
Ellsworth City
3
2.
Bangor
10
9.
Norway
2
3.
Augusta-Winslow
10
10.
Belfast City
2
4.
Lewiston
10
11.
Rumford
2
5.
Sanford-N. Berwick
7
12.
Newport
2
6.
Brunswick
6
13.
Farmington
2
7.
Rockport-Warren
4
14.
Dover-Foxcraft
1
TOTAL:
Centroid
MW
79 MW
It must be recognized that there are considerable, perhaps insurmountable, obstacles to
realizing this small potential.
Among the most serious are:
Institutional and public resistance to regional collection and
processing of waste on such an unprecedented scale in Maine.
Logistical problems in truck transportation of MSW or RDF (other
modes
are not practical in Maine because of the low population
density and amounts of waste [Table 4.5]).
Availability of suitable boilers for burning RDF.
The use of technologies other than waterwall incineration or RDF conversion may be practical
for small-scale applications in specific locations, but do not appear promising as means for producing
bulk supplies of electricity for the public in Maine.
The low- and medium-Btu gas produced by pyrolysis
or biological processes must be used relatively near the production site, requiring large collection
distances to produce significant amounts of energy.
Processes producing supplementary liquid fuels
have lower efficiencies and face the same logistical problems as RDF systems.
G-25
Table 4.5
Comparison of MSW Transport Modes
MODE
CONDITIONS CONDUCTIVE TO THE MODE
LIMITING CONDITIONS
TRUCK
A.
Packer drives to Utility
Co-locate Processing Plant
Congestion of Packers at Drop-off;
Noise; Esthetics
along route
B.
Transport Van
60 or 75 cu. yd.
Congestion of collection vehicles; maneuverability; weight
limits; low speed;
central land avail-
ability
BARGE
Limited Road Access
Waterway Access
High Volume of Waste
Unloading Facilities
Waterway with deep
ports
High Capital Cost
RAIL
HAUL
High Population Density;
Remote Power Plant (at least 40
miles); High Volumes of Waste
(1000 TPD); Rail Spur to Power
Plant (Single use train service)
Availability of cars;
Loading/Unloading
Facilities; Scattered
Population
PIPELINE
Very high population density;
Large volumes; Limited truck
access; Short distance from
processing to utility (one mile
or less)
Cost
Construction difficulties
from (Ganotis, 1974, p. 47)
5.0
ENVIRONMENTAL IMPACTS
Any scheme to produce electricity from MSW will produce two sets of environmental impacts.
first set of impacts results from the collection of refuse and its transport to the
sion facility.
The
energy conver-
The second set of impacts results from the construction and operation of the con-
version facility.
It is not possible to quantify impacts for each centroid of collection mentioned
in Section 4 with presently available data.
5.1
Collection and Transport
A transfer station network is the most economical and environmentally sound option for collecting
solid waste in a large region and transporting it to a single processing site.
In such a system,
collection would be performed on a local basis, much as it is today, using trucks or private vehicles.
Instead of being taken to a landfill, the MSW would be carried to a transfer station.
Some prepro-
cessing, such as the removal of bulky noncombustibles, can be performed at the transfer station, but
the major advantage lies in the use of larger capacity trucks for moving MSW from the transfer station
to the energy conversion plant,
Environmental impacts arise from the effects of collection and transfer truck traffic from
the construction and operation of the transter stations.
The most significant impacts occur as
increased air pollution (from truck exhaust), noise (trucks and transfer station), and land use (transfer stations and roads).
actual
To determine the magnitude of these impacts requires the planning of the
transfer station system for the region.
G-26
Designing a transfer system can be a complex optimization problem.
Data (or assumptions) are
needed on MSW generation patterns, collection and transfer truck capacities and costs, possible transfer station sizes and sites and the location, allowable speeds and capacities of roads.
Depending
on these data, the design can be obvious, or can require increasingly sophisticated processing until
only computerizedoptimization
models can find a solution (Ganotis, 1974, p. 39).
acceptable transfer station system can be designed.
not economically viable.
For some data, no
For other data, a design may be feasible, but
Case studies of the design of transfer station systems are given in (Ganotis,
1974) and (Cousins, 1976, p. 303).
(Berman, 1976) discusses the use of a computerized planning
model on eastern Massachusetts.
The transfer station system design will determine the number, capacity and approximate location
of transfer stations, and the number of collection and transfer truck trips required.
These data
can be combined with truck mileage efficiencies and emissions data (Table 5.1) to yield truck emissions and new traffic patterns in the region.
Table 5.1
EMISSION FACTORS FOR DIESEL AND GASOLINE ENGINES
Pollutant
Diesel
Emission Rate*
(lbs/lOO gallons of diesel)
Gasoline.
Emission Rate**
(lbs/1000 vehicle miles)
Aldehydes
10
0.3
CO
60
165.0
Hydrocarbons
180
12.5
NO 2
222
8.5
SO 2
40
0.6
Organic Acids
31
0.3
110
0.8
Particulates
from (Cousins, 1976, p. 333)
Collection and transport problems are generally the same for incineration and RDF systems.
RDF systems would have increased transport impacts as the RDF was shipped from the processing plant
to the sites where it would be burned.
G-27
5.2
Conversion Facility
Environmental impacts vary significantly from one conversion process to another.
Processes which
produce a refuse-derived fuel (RDF) generate some of their impacts at the site where the RDF is burned.
5.2.1
Incineration
The most significant air pollutant from incineration of MSW is particulate matter.
Uncontrolled
particulate emissions are usually high enough to violate Federal standards, but existing large MSW
incinerators have been successful in meeting particulate standards by using electrostatic precipitators
(Stabenow, 1972, p. 2).
These devices remove 95-98% of the particulates in the flue gas.
Other air pollutants include sulfur dioxide (S02),
nitrogen oxides (NOx), and hydrocarbons.
hydrogen chloride (HC1), carbon monoxide (CO),
Sulfur dioxide emissions, because of the low sulfur content
of MSW (0.1%), are lower than those produced by burning distillate fuel oil.
is needed.
No SO 2 control equipment
Hydrogen chloride is produced primarily by the combustion of plastics and should not re-
quire control equipment.
Carbon monoxide and nitrogen oxide production can be regulated by controlling
furnace operating conditions.
Emissions of these pollutants should be within acceptable ranges.
Hydro-
carbons are controlled through a high rate of combustion and are released in only small amounts.
Quantification of these pollutant emissions requires knowledge of the particular incinerator design being used, the characteristics of the MSW being fired, and the operating conditions of the
combustion region.
Evaluation of their ambient impact would further require meteorological and
topographical data for the proposed site,
In general, a well designed incinerator should be able to
meet all applicable ambient standards (Table 5.2).
Table 5.2
Comparison with Ambient Air Quality Standards for N.E, Massachusetts Incinerator
Pollutant
Particulates
Max Increment
from ProposedFacility**
3
(jg/m
)
3
Ambient Standard*(g/m
)
Annualgeometric
mean
Annual average
Max 24-hour
60
0.44
150
0.46
3.6
50°2o~ll 5)Annual
(@ .1% S)
average
Max 24-hour
Max 3-hour
80
365
1,300
0.8
6.3
5.2
NOy
Annual average
100
1.5
10,000
40,000
14.1
20.1
(@150 ppm)
CO
Max 8-hour
Max 1-hour
HC1
(@ 400 ppm)
Annual average
Max 24-hour
Max 8-hour
(@150 ppm)
3.3
25.7
49.9
none
none
none***
Maximum concentrations
may be exceededonce per year. The more stringentstandardsare presented.
For 5,000 Btu/lbrefuse; annual averagesbased on 2,570tons/day,maxima on 3,450 tons/day. Maximaoccur
at A stabilityand wind speed 3.0 m/sec. Note: for HaverhillMonitoringSite locationmultiplyannual
values by 0.2, maxima by 0.8.
Occupational8-hour exposurelimit is 7,000 g/m
from (Cousins, 1976, p. 323)
G-28
.
Noise would result from the incineration plant operation and from transfer vans arriving and
unloading MSW.
Good facility design should keep noise levels within acceptable ranges.
The largest water use is in the cooling towers required for electricity production.
In the
N.E. Massachusetts incineration proposal, 2.3 million gallons per day will be required for a 3000 TPD
facility.
Cooling tower losses represent 93% of the total (Cousins, 1976, p. 353).
Since incinera-
tion is less efficient (21%) than conventional fossil fuel generation (35-39%), as much as 30% more
cooling water will be required.
The overall system can be designed to avoid any disposal of waste
water into local water bodies, thus preventing direct water pollution problems.
Incinerator residues present several possible impacts.
First the residues must be discarded.
Compared to raw MSW, the residues are more compact 0/5 the volume) and can readily be used for landfill.
Some dust problems may arise during storage and shipment of the residues.
is the potential for leaching of toxic heavy metals (Table 5,3).
The greatest concern
This must be addressed on a site-
by-site basis to prevent contamination of groundwater supplies.
Table 5.3
Heavy Metals Present in Leachings from MSW Residues and Processing
Constituent
Average
Constituent Concentration (mg/l)
Cadmium
0.04
Total Chromium
0.055
Copper
0.10
Total Iron
.
0.45
Lead
0.165
Nickel
0.19
Tin
18.5
Zinc
0.06
Limit for
Drinking Water (mg/l)
0.01
0.05
1
0.3
0.05
5
from (Cousins, 1976, p. 356)
5.2.2
Refuse-Derived Fuels (RDF)
RDF systems produce impacts at the processing plant and at the site of combustion.
Since RDF
has been used only as a supplementary fuel, a conventional fossil fired boiler is needed, with all
of its associated impacts.
These conventional impacts will not be discussed here.
The most extensive environmental testing of a fluff RDF processing plant was performed by the
EPA at St. Louis.
The areas of environmental impact tested were air emissions, water runoff, and
noise.
Air emissions occurred from both the air classifier and the hammermill shredders in the St.
Louis plant.
These were particulate emissions since no combustion occurs in the RDF processing,
The air classifier released an average of 1.25 lb of particulates per ton of processed MWS.
data ranged from 0.50 lb/ton to 1.70 lb/ton,
control measures (Shannon, 1975, p. 56).
lb/ton (Shannon, 1975, p. 62).
Test
This is a significant quantity and would require
The hammermill shredders generated between 0,005 and 0.03
Further emissions occur from dust and blowoff from conveyors,
but these have not been quantified.
Water runoff was due to plant dust control measures, and did not include water runoff from the
MSW, which had to be separately controlled and treated,
because of the small volumes of water used (2000
Water runoff was found to be insignificant
4000 gal/week).
Noise was caused principally by the hammermill, the metals separator, the air classification
system exhaust, trucks and transfer vans and the front-end loader used to move the waste within the
plant.
Within the St. Louis plant, two locations registered as high as 110 dBA.
One was below
the metals separator as magnetic materials dropped into a collection chute and the second was next
to the collection trucks while they unloaded.
Because all high noise levels were either of brief
duration or in remote locations, the Federal OSHA noise level standards were not violated.
G-29
Maximum
noise levels observed outside the plant but within the plant grounds ranged from 76 to 95 dBA
(SHannon, 1975, p. 69).
The fluff RDF was fired as a supplementary fuel in Union Electric's Meramec Plant under boiler
loads of 75 and 140 MW.
The RDF contributed from 9 to 27% of the total heat input.
No significant
changes in SO 2 , NOx , or CO pollutant emission levels were observed during RDF firing (Shannon, 1974,
p. 40) (Table 5.4).
Moderate average C'
emissions were noted.
Table 5,4
Emission
Levels During RDF Firing at St. Louis
Coal (a)
Component
6.8
943
9
298
335
H 0, Percent
S82. ppm
No, ppm
C1, mg/m
Coal RDF (b)
8.6
1067(c)
8
285
402
(a) Average for 3 coal tests
(b) Ayerage for 10 coal-refuse
(C) 13%increase in SO2 emissions during coal-RDF
tests resulted from a 24% increase in coal
sulfur content.
from (Kilgroe, 1976, p. 423)
It was observed that particulate emissions increased with RDF firing, but this is believed to
be due to an efficiency reduction in the plant electrostatic precipitator (ESP) due to increased
gas volumes when burning refuse (Figure 5.1).
Particulate loadings at the input to the ESP were
the same for coal only and coal + RDF operations.
It should be possible to "tune" the ESP to
various RDF conditions, in which case particulate emissions would be roughly equivalent for both
coal and coal + RDF firing (Shannon, 1974, pp. 66-68).
Figure 5.1
E
0.8
w
I-
0
0.6
Q.
U,
w
z0
0.4
C,
u,
-
0.2
-J
a.
n
150
200
'
250
300
GAS FLOW RATE AT ESP INLET, m 3 /s
EFFECT OF YOLUMETRIC GAS FLOW RATE ON PARTICULATE EMISSIONS
from (Kilgroe, 1976, p. 422)
G-30
350
Boiler residues were found to be 4 to 7 times as high for coal + RDF firing, on the order
of 4.5 tons/hour (4350 Kg/h) (Figure 5.2).
Besides coal ash, both inert MSW particles (glass,
metals, etc.) and unburned MSW particles (wood, leather, etc.) are present in the residues.
Three parameters in the ash disposal pond were found to exceed the proposed guidelines for Missouri:
biological oxygen demand (BOD), dissolved oxygen, and suspended solids (Kilgroe, et al.,
1976, p. 423).
Controls for these parameters will probably be required.
Figure 5.2
6000
5000
. ...............
O
.
15,570
.
4000
z
3000
o0.
f-
In
a
al
2000
0
i
1
1000
I
70
O
_· _O'
I
80
I
I
90
I
i
I
REGULAR
1o
GRIND
04
I
I
I
100
110
120
GENERATION RATE MEGAWATTS
I
I
130
REFUSE
I
140
BOILER RESIDUE ACCUMULATION RATE FOR COAL AND COAL-RDF
A commercial demonstration of fluff RDF, based on the Union Electric test results was to have
been implemented in St. Louis.
Public opposition to traffic and transfer station siting caused
repeated delays and the project was finally dropped (ELP, 1977).
Environmental impact data for dust RDF systems was not available.
no residue disposal and no waste water treatment will be required.
The developers claim that
Fabric filter systems will con-
trol particulates and all existing and anticipated EPA and OSHA regulations will be met (ADL, 1976,
p. 14).
G-31
6.0
ECONOMICS
A number of alternative arrangements can be made for converting MSW to electricity.
The eco-
nomics and reliability of the final electricity supply will depend upon which alternative is implemented.
All operations reported to date have concentrated on finding the lowest waste disposal costs for
a town or region.
When electricity has been a byproduct it has been priced to compete with conven-
tional generation (20-40 mills/kwh) so as to ensure a minimum reliable income to the disposal facility.
Similarly, facilities producing steam with sufficient temperatures and pressures for electricity production have assigned competitive costs to the steam to ensure revenues to the disposal operation.
It has usually been assumed in these cases that the purchaser of the steam will buy and operate the
turbine/generator equipment.
The difference between the costs of collection and the revenues from
the sale of electricity or steam (and recovered materials) has been the net disposal cost per ton to
communities.
If refuse to energy facilities are built and financed in Maine by communities interested in
economic solutions to their waste disposal problems, the resulting electricity or steam will have to
be priced to compete with the energy from conventional utility generation.
revenues for the disposal operation will not be guaranteed.
a dedicated user rather than sold to electric utilities.
provides General Electric with steam.
Otherwise, long-term
Of course, the energy may be given to
For example, the RESCO plant in Saugus, Mass.,
Costs are set on the basis of the costs for steam production
using conventional fuels (Papamarcos, 1974).
If the refuse to energy facilities are built by electric utilities for the purpose of utilizing
an indigenous renewable fuel supply, then it would be the disposal charges to communities which would
have to compete with charges for alternative disposal methods, including the construction of the
communities' own refuse to energy plants.
guaranteed.
Otherwise, a long-term reliable
fuel" supply will not be
Electricity costs would be the difference between annual costs and annual revenues
from disposal charges and materials recovery.
These alternatives are further complicated by issues such as
public vs private financing of the waste to energy facility
utility reluctance or regulatory opposition to utilities' becoming MSW
processing companies
community reluctance or inability to become responsible for providing a
reliable electricity supply
current uncertainty of cost figures due to site-specific factors, the
general lack of commercial experience with refuse to energy technologies,
and the variety of assumptions used by researchers, architect-engineers, and
regulatory groups in making estimates of costs.
Considering all of the possible variables, it is obviously difficult to assign "typical" costs
for various refuse to electricity systems (See [Levy and Rigo, 1976, p. 18]). We will nonetheless
attempt to provide some information concerning collection and transport costs and conversion costs
for incineration and refuse derived fuel systems.
As more full-size plants are in operation, the
EPA's Office of Solid Waste Management will be compiling the non-proprietary data on their costs.
G-32
6.1
Collection and Transport
It is impossible to assign accurate collection and transport costs without a specific collection
scheme in mind.
As mentioned in Section 5.1, the design of such a scheme is non-trivial and requires
a substantial preliminary data collection effort which is beyond the scope of this study.
We will
only attempt to identify the important cost components and their range of values in this section.
Refuse collection begins at the local levels and is usually done on a contracted basis by each
local government.
Collection costs will vary with the size and type of the vehicle, crew size, the
distance covered on the collection route, and the speeds at which the vehicle can travel (Table 6.1).
These costs will vary from community to community as functions of population densities, MSW generation
rates, and road conditions.
Table 6,1
Transport Cost in Dollars Per Ton Per Mile
Miles Per Hour
35
40
45
60
50
15
20
25
30
0.202
0.298
0.'394
0.151
0.223
0.295
0.121
0.179
0.236
0.101
0.1.49
0.197
0.076
0.08610.0670.061
0.128 0.112 0.099
0.169 0.148 0.131
0.355 0.237
0.535 0.357
0.715 0.477
0.178
0.267
0.357
0.142
0.214
0. 286
0.118
0.178
0.238
0.101
0.153
0.204
0.089
0.134
0.179
0.079 0.071 0.065
0. 119 0.107 0.097
0.159 0.143 0.130
0.059
0.089
0.119
0.603 0.301
0.201
0.151
0.121
0.101
0.086
0.075
0.067
0.061
0.055
0.051
0.694 0.347
0.231
0.174
0.139
0.116
0.099
0.087
0.077
0.069
0.063
0.058
0. 2Z4 0.149
0.119
0.089
0.075
0.064
0. 056
0.049
0.045
0.041
0.037
0. 326 0.163 0.109
0.081
0.065
0.054
0.047
0.041
0.036
0.033
0.029
0.027
0.265
0.066
0.053
0.044
0.038
0.033
0.029
0.026
0.024
0.022
5
10
25 Yd Re..r End
Loader
1 Man Crew
2 Man Crew
3 Man Crew
0.605 0.302
0.893 0.446
1.181 0.590
0.089
0.118
0.055 0.051
0.081 0.074
0.107 0.098
20 Yd Rear End
Loader
I Man Crew
2 Man Crew
3 Man Crew
30 Yd Front
0.710
1.070
1.430
End
Loader
I Man Crew
25 Yd Front End
Loader
1 Man Crew
40 Yd Roll-On
Roll-Off
Refuse Coll.
I Man Crew
0.448
65 Yd Transfer
Trailer
I Man Cre*
Inc. Residue
40 Yd Roll On
Roll-Off
1 Man Crew
0. 132 0.088
from (Ganotis, 1974, p. 44)
At some point, it becomes more efficient to construct a transfer station than to haul MSW
increasing distances with relatively small collection vehicles.
The transfer stations can per-
form several functions, including some preprocessing such as the removal of bulky items, non-combustibles,
and hazardous materials.
Their most important function is to compact the raw MSW and load it into
larger, more efficient transfer vehicles for transport to the nearest conversion facility.
could involve truck, rail, pipeline, or barge transport in general.
This
For Maine, truck transport is
probably most practical although one study has indicated Maine's rail system would be more economic
G-33
for distances over 75 miles (Hubbell in Dearborn, et al., 1974, p. 114).
The design choice of transfer station locations will be a complex trade-off of rising local
collection costs, transfer station investment and the costs of the various transportation options.
Since transportation costs vary with capacity (Figures 6.1 and 6.2), a larger collection area is
desirable.
Transfer costs by truck are reflected in Table 6.1. Another estimate, assuming a 75 cu. yd.,
20-ton transfer vehicle capacity yields a cost of roughly $0.10 per ton mile for a 50-mile haul
(Figure 6.3). These costs and the design of the transfer system will depend strongly on the location
of the central conversion facility and the adequacy of the intervening highway system to handle
large trucks.
Figure 6.1
10
9
8
7
6
5
-
tn
c c
_
f;
Ex
rO
c
4
3
-
-o
:
rED~
2
3
4
5 6 7 8 9 10
20
30 40
Capacity
TPD x 101
5060708090100
200
TRANSFERSTATIONINVESTMENTVERSUSCAPACITY
from (ADL, 1976, p. 30)
Figure 6.2
3..
2.5
2.0
U,
S..
'U
r_1
0
'.
I0h
8
C
.0
0
c
O
1.0
0
00
0.5
0
0
from (ADL, 1976, p. 31)
200
400
600
800
Capacity
(TPD)
1000
1200
TRANSFERSTATIONOPERATINGCOSTS
G-34
1400
1600
Figure 6.3
7.00
&6.00
5.00
S-
to
.
8
4.00
.Z
I -.
2.00
.e~~~~
~~~~~~~~~~~~~~~~~~~~··
0
0
10
20
30
40
50
60
70
80
90
100
One-WayTrip Mileage
(miles)
TRANSPORTATIONCOSTFORSOLID MUNICIPAL WASTE
from (ADL, 1976, p. 32)
6.2
Conversion Facility
The costs of construction and operating a conversion facility depend on the technoogy used,
site acquisition, and preparation, construction costs, labor, materials, and equipment.
Annual
costs are further determined by interest rates, capital structure, taxes, plant availability, and
production, wage and utility rates, disposal costs, and O&M costs.
In general, annual costs for
converison are between $10 and $25/input ton (Levy and Rigo, 1976, p. 19).
6.2.1
Incineration Systems
The estimated capital costs of incineration systems under construction or in operation range
from $11,500/input ton of capacity to $29,200/input ton (Table 6.2)
as high as $36,700/input ton (Standrod, 1977).
Recent rough estimates are
These agree with the range of $21,500 to $39,000/input
ton given in (Rofe, et al., 1975, p. 60) and the range of $10,400 to $30,800/input ton given in
tCousins, et al., 1976, p. 266).
Note that most of the plants do not produce high quality steam,
so costs for an electricity producing system would be even higher.
In addition, there would be
the investment required for the electrical plant itself.
Annual operation and maintenance costs have been observed to vary in the range of 5 to 10% of
plant investment (Rofe, et al., 1975, p. 60) (Schultz, et al., 1975, p. 10) depending on the size of
the plant and upon accounting functions.
G-35
Table 6.2
Incineration Systems Estimated Capital Costs*
Capital Cost
Design Capacity
Ton per Day
Location
Steam Conditions
1000 lb/hr-psig/°F
Capital Cost
per input ton
$106(yr)
$103
720
270
400/600
17 (1974)
23.6
Saugus, Ma.
1200
370
890/875
35 (1975)
29.2
Quebec City, P.Q.
1000
162
680/600
25 (1974)
25.0
600
212
250/590
9 (1974)
15.0
1600
440
275/414
30 (1972)
18.8
720
183
250/456
Nashville, Tenn.
East Hamilton, Ont.
Chicago, Ill.
Harrisburg, Pa.
Hempstead, NY
2000
Estimated**
4000
/I
-~~~~
_
Estimated**
_/ _
1500
8.3 (1972)
55 (1975)
115-120 (1977)
50-55
(1977)
11.5
27.5
30.0
36.7
*from (Parkhurst, 1976)
**from (Standrod, 1977)
6.2.2
Refuse Derived Fuel (RDF) Systems
The estimatedcapital costs of RDF systems under construction or in operation range from $7200/input
ton of capacity to $28,000/input ton (Table 6.3).
Other estimates have placed the costs between $4,600
and $9,500/input ton (Rofe, 1975, p. 70) and between $8,800 and $27,500/input ton (Cousins, 1976, p. 266).
These costs do not include special modifications which may be required in existing or new boilers
for the use of RDF.
Table 6.3
RDF Systems Estimated Capital Costs
Lncation
-II· · ·- · ·
Design Capacity
Ton
Der
Day
---r-- ·I
St. Louis, Mo.
315
Ames, Ia.
200
Bridgeport, Conn.
Berlin, Conn.
Milwaukee, Wis.
Baltimore, Md.
1500
800-1400
1000
Capital Cost
per input ton
$103
Fuel TDe
'·
Capital Cost
106 (yr)
-L
Fluff RDF
2.5 (1972)
7.9
5.6 (1975)
28.0
29.3 (1976)
19.5
II
I"
Dust RDF
22.0 (1975)
27.5 - 15.7
Fluff RDF
18.0 (1975)
25.0 - 8.3
10.0 (1975)
18.0
400-1200
Chicago, Ill.
2000
14.3 (1973)
7.2
Akron, O.
1000
24.0 (1975)
24.0
St. Louis, Mo.
8000
80.0 (1976)
10.0
from (Parkhurst, 1976)
G-36
Annual operating and maintenance costs for RDF systems have also been observed or projected
in a range from 5% to 10% of investment costs.
The increased O&M costs at the plant burning the
RDF are separate.
Based on the St. Louis RDF demonstration project, which involved modification of the coalfired boilers at the Meramec Plant, the combined increase in capital and operating expenses have
been estimated. These can vary according to existing ash handling and fuel feed facilities. Under
favorable conditions, the increased annual cost might be as low as $0.50 to $1.00/ton (1973
dollars).
If ash handling equipment must be installed and air pollution particulate controls added, the
costs
can be as high as $2.50 to $5.00/ton (1973 dollars) (Lowe, 1973, pp.19-20).
Other estimates for boiler modification, electrostatic precipitators, etc. result in higher
figures. The important point to be made is that retrofit of existing boilers in Maine can be
extremely expensive. Compilation of data from the literature [Giglio, in Dearborn, 1974, p. 36,
etc.] results in the following estimates in 1974 dollars.
Capital
Investment
$/ton/yr
I
I
.
Boiler
Modification
$300,000
22
Electrostatic
Precipitators
$1,250,000
91
Fixed Charges
II PriVate
221/2%
$/ton/yr
Public
12 1/2%
$/ton/yr
5
3
21
11
j
. _____________________________
_ I_
6.2.3. Dumping Charges
The price a town or refuse contractor pays to dump collected refuse is referred to as the tipping
or
dumping charge. It is affected by a variety of market conditions, the most important of which are
land availability and the stringency of environmental requirements for dealing with the dumped
refuse. The major problem in Maine today is the elimination of open dumps and the consequent need
for either landfill systems or waste processing.
Figures from various existing disposal systems
including energy recovery have ranged from roughly $4 to $13/ton (Parkhurst, 1976)(Cousins, 1976,
p. 289).
6.3 Discussion
Given the large uncertainties in available cost information,and the lack of a specific system
design, it is difficult to determine a final cost figure for electricity produced by a utility-owned
and operated wastes-to-energy system. Tables 6.4 through 6.7 providean optimistic, rough, order-ofmagnitude computation for comparison with other alternatives.
G-37
The following assumptions are used:
All costs are 1986 dollars, using a 5%/year simple inflation rate
A three-tier system of collection and processing is used to obtain processing
economies of scale (see Figure 4.1):
North:
Centroids 2, 8, 10, 12, 14 (2 has conversion plant)
Central:
South;
Centroids 3, 7, 9, 11, 13 (3 has conversion plant)
Centroids 1, 4, 5, 6:
(1 has conversion plant)
Collection in the centroids is made at the expense of the communities; MSW
is delivered to a central transfer station in each centroid where a dumping
fee of $10/ton is charged.
Centroids 1, 2, and 3 deliver MSW directly to the conversion plant.
Our optimistic estimates of final costs are seen to be in the range of 43 mills/kwh (RDF) to
63 mills/kwh (incineration).
Note that these are optimistic costs for the following reasons:
Generating equipment and boiler modification costs are completely ignored.
It is unlikely that all communities will cooperate to achieve such volumes of
collected MSW at central locations, leading to smaller economies of scale and
higher costs.
Heat contents less than the assumed 6200 Btu/lb will often occur, with proportionally higher costs (see last column
G-38
of Table 6.7) from 59 to 87 mills/kwh,
Table 6,4
Hypothetical Utility-Operated Waste-to-Electricity System Costs
Collection System
(1986 dollars1 )
Annual ICosts - $103
Centroid
North
i
2
I
Dumpinq Fee
30
157
136
(285)
10
75
35
148
124
(225)
12
67
30
129
96
(201)
45
40
105
81
(135)
A
TOTAL
(969)
95
i
14
South
5
TranspDort
4
Trans. Station
Miles3
323
8
A I . I
central
2
MSW-TPD
(89i
I
i
I
3
3IZ
7
128
35
9
75
55
11
70
13
64
1
569
4
i
(986)
187
213
(384)
l
148
178
(225)
50
i,
135
151
(210)
30
i
132
91
(192)
i
.
I
(1707)
301
40
541
(903)
5
212
30
223
306
(636)
6
176
30
150
-253
(528)
1
265
(712)
(2036)
II
l
15% per year simple inflation
2
Table 4.3
3
Figure 4.1
4
Figures 6.1 and 6.2
5
Figure 6.3
Table 6.5
Hypothetical Utility-Operated Waste-to-Electricity System Costs
Incineration System
OPERATING COSTS
CAPITAL COSTS $106
MSW-TPD
TOTAL1
ANNUAL 2
$106
3
ANNUAL TOTAL $106
North
605
38.4
6.9
3.1
10.0
Central
649
41.2
7.4
3.3
10.7
1258
79.8
14.4
6.4
20.8
South
1
Assuming $35,000/ton (1977 dollars), design capacity equal to 1.25 times average capacity, turbine
and electrical equipment not included.
218% levelized carryin
3
charge
At 8% of total capital investment
G-39
Table 6.6
Hypothetical Utility Operated Waste-to-Electricity System Costs
RDF System
OPERATING COSTS 3
CAPITAL COSTS $106
MSW-TPD
TOTAL1
605
27.4
649
29.4
5.3
1258
57.0
10.3
North
Central
South
1
i
ANNUAL
$10
49
ANNUAL TOTAL
2.2
1
$106
7.1
2.4
7.7
4.6
14.9
Assuming $20,000/ton (1977 dollars), design capacity equal to 1.25 times average capacity, boiler
modifications not included.
218% levelized carrying charge
3
At 8% of total capital investment
Table 6.7
Hypothetical Utility Operated Waste-to-Electricity System Costs
I
COSTS $106
{ ANNUAL'
MSW--TPD
North
South
A
106 KWH
COLLECTION
649
145.2
155.8
1258
301.9
(0.8)
(0.7)
(2.0)
t I
602.9
(3.5)
605
Central
!
PROCESSINGZ
10.0-7.1
41.5-29.7
i
I
1
MILLS/KWH
MILLS/KWH
63-43
64-45
62-43
10.7-7.7
20.8-14.9
87-59
88-62
85-59
i
IUI AL
i
87-594
63-434
.
1300 days/yr, 6200 Btu/lb, 22% efficiency
2
High cost:
incineration; low cost: RDF
34500 Btu/lb
4
I
See discussion in Section 6.3 for discussion of optimistic nature of these costs.
7.0
CONCLUSIONS
By 1986 Maine will be producing on the order of 3000 tons per day (TPD) of
municipal solid wastes (MSW).
This waste theoretically could have the
energy equivalent of a 95 MW generating plant.
The dispersed nature of the wastes presents serious collection problems.
If
the 14 largest concentrations of population were to cooperate in a waste-toenergy program, about 75 MW potential would exist.
The five largest would have
the potential for 35-40 MW, assuming complete cooperation.
The most promising and experienced technologies for electricity production are
incineration and refuse-derived fuel (RDF) systems.
RDF systems require the
existence or construction of a coal-fired plant to burn the fuel.
G-40
3
Environmental impacts consist of increased particulate and possibly heat
emissions, noise, and traffic.
When compared to existing waste disposal
methods, incineration and RDF systems are more desirable.
Compared to
burning conventional fuels, incineration has greater heat and particulate
discharges, but lower SO 2 impacts.
RDF increases particulate loadings.
Costs for collection, transport, and conversion vary widely and are
strongly site- and design-specific.
Utilities would receive energy from
municipal or regional conversion facilities at a price competitive with
other fuels. Costs for a utility-operated system would range upwards
from optimistic figures between 60-90 mills/kwh (1986 dollars).
Institutional, legal, and cost uncertainties, combined with the low energy
potential, make the initiation of a utility-owned waste-to-energy collection
and conversion system in Maine a highly risky venture.
It may be economically
attractive for utilities to use RDF or steam purchased from municipally
owned and financed MSW systems, but this will have to be decided on a caseand site-specific basis.
Such systems will not offer significant amounts of
energy in comparison to Maine's electrical supply requirements.
G-41
8.0
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G-45