ENERGY AND POLLUTION PREVENTION
nr
Market Opportunities for
Biogas Recovery Systems
A Guide to Identifying Candidates
for On-Farm and Centralized Systems
-------
How to Use This Guide
AgSTAR developed this guide to characterize the market opportunities for biogas energy for
greenhouse gas reduction projects at swine and dairy farms in the United States. The guide
identifies the states with the greatest opportunity to cost effectively install and operate biogas
recovery systems using dairy and swine manure. This report is intended for anyone interested or
involved in the development of renewable sources of energy; distributed generation; or the
development, design, and financing of biogas systems at animal feeding operations. The guide
is organized as follows:
• The section on Biogas Recovery Systems explains the types of systems in use today.
• The benefits of biogas recovery systems for odor control, water quality protection, and
greenhouse gas emission reductions are explained in Substantial Environmental
Benefits.
• Identifying Profitable Systems describes the type and size of animal operations where
biogas recovery systems are estimated to be technically feasible.
• Energy Production Potential summarizes the market potential for methane production
and electricity generation nationally. The state profiles at the end of the guide
characterize dairy and swine operations in the states with the greatest potential for
biogas recovery. The profiles show the sizes and types of operations, the estimated
number of feasible operations, methane production potential, associated electricity
generating potential, and potential methane emission reductions.
• The Appendix explains the methodology used to estimate market potential.
EPA-430-8-06-004
www.epa.gov/agstar
-------
Contents
Introduction 1
Biogas Recovery Systems 1
Substantial Environmental Benefits 2
Identifying Profitable Systems 3
Energy Production Potential 4
Top 10 states for Electricity Production from Dairy and Swine Manure 5
About AgStar 6
State Profiles 7
North Carolina: Swine 8
Iowa: Swine 9
Minnesota: Swine 10
Oklahoma: Swine 11
Illinois: Swine 12
Missouri: Swine 13
Indiana: Swine 14
Nebraska: Swine 15
Kansas: Swine 16
Texas: Swine 17
California: Dairy 18
Idaho: Dairy 19
New Mexico: Dairy 20
Texas: Dairy 21
Wisconsin: Dairy 22
New York: Dairy 23
Arizona: Dairy 24
Washington: Dairy 25
Michigan: Dairy 26
Minnesota: Dairy 27
Appendix: Methodology 29
State Animal Populations and Farm Profiles 30
Manure Management Practices 30
Methane Emissions Equation 31
Biogas Production and Electricity Generating Potential 31
References 32
Example Calculations: Impacts of a Biogas Recovery System Replacing a Manure Storage
Facility and a Conventional Anaerobic Lagoon 33
Methane Conversion Factors by State for 2003 (percent) 34
-------
-------
Market Opportunities for
Biogas Recovery Systems
A Guide to Identifying Candidates for
On-Farm and Centralized Systems
Biogas recovery systems at livestock and poultry
operations can be a cost-effective source of clean,
renewable energy that reduces greenhouse gas
emissions. Because of its high energy content, biogas can
be collected and burned to supply on-farm energy needs
for electricity or heating. In 2005, about 100 systems
were operational or under construction in the United
States, and another 80 in the planning stages. However,
biogas recovery systems are estimated to be technically
feasible at about 7,000 dairy and swine operations in the
U.S. These facilities offer a substantial business oppor-
tunity to increase farm income. Biogas recovery systems
at these facilities have the potential to collectively
generate up to 6 million megawatt-hours (MWh) per
year, and displace about 700 MW of fossil fuel-fired
generation on the electrical grid (Figure 1).
Biogas is produced when the organic matter in manure
decomposes anaerobically (i.e., in the absence of oxygen).
Biogas typically contains 60 to 70 percent methane, the
primary constituent of natural gas, and is a clean-burning
fuel. The potential for generating methane is greatest
when manure is collected and stored as a liquid, slurry,
Figure 1 . Market Opportunities for Biogas
Recovery Systems at Animal Feeding Operations
Animal Sector
Swine
Dairy
Total
Candidate
Farms
4,300
2,600
6,900
Electricity Generating Potential
MW
363
359
722
MWh/year
3,184,000
3,148,000
6,332,000
or semi-solid. Because the vast majority of large dairy
and swine operations in the U.S. use liquid or slurry
manure management systems, the biogas production
potential is greatest at these operations; and the
greenhouse gas reductions are the most significant. Other
animal sectors manage manure primarily in solid form,
making energy conversion costly and offering little
opportunity for greenhouse gas reductions.
Biogas Recovery Systems
A biogas recovery system has four components:
• Manure collection system. Existing liquid/slurry
manure management systems can readily be adapted to
deliver manure to the anaerobic digester.
• Anaerobic digester. An anaerobic digester is designed
to stabilize manure and optimize the production of
methane. A facility for digester effluent storage is also
required.
• Biogas collection system. Biogas is collect-ed and piped
to a combustion device.
Gas use device. Biogas can be used as a
boiler fuel for space or water heating, but
more commonly is used to power
reciprocating engines to generate
electricity for on-farm use, with excess
electricity sold to the local public utility.
Flares always are installed to combust the
biogas during periods when a gas use
device is not available.
While other biogas recovery systems are
available, the three most prominent designs
currently used at U.S. farms (Figure 2) are
described below. Typically, covered anaerobic
-------
lagoons are less costly than complete mix or plug-flow
systems, but cannot be used for energy applications
above the 40th parallel due to low average ambient
temperatures (more methane is produced at higher
temperatures).
Covered anaerobic lagoon1: An anaerobic lagoon is
among the simplest and most common manure storage
and stabilization systems currently in use. A flexible
cover is installed over the lagoon, and the methane is
recovered and piped to the combustion device.
Plug-flow digester1: A plug-flow digester has a long,
narrow tank with a rigid or flexible cover. The tank is
heated and often built partially underground to reduce
heat loss. Use of plug-flow digesters is limited to dairy
manure collected by scraping.
Complete mix digester1: A complete mix digester is an
enclosed heated tank with a mechanical, hydraulic, or
gas mixing system. Complete mix digesters work best
when there is some dilution of the excreted manure with
process water (e.g., milking center wastewater).
Centralized biogas systems. In general, on-farm biogas
recovery is most feasible at larger operations. However,
centralized systems make it possible to develop an econom-
ically successful venture by combining the manure from
several farms within a region. A centralized system may be
designed and operated by a corporation, a cooperative, or a
third party such as an energy company. Two centralized
systems are in operation today. The potential advantages of
centralized biogas production include:
• Economy of scale—Experience demonstrates
significant economic benefits as biogas production
capacity increases.
• Marketing leverage—The ability to provide a significant
supply of energy may be an advantage in negotiating
contracts for the sale of electricity to the local utility.
• Financing—Due to the scale of the project, additional
sources of venture capital may be available as well as
assistance from grants, tax credits, or renewable energy
programs.
• Third party management—Livestock producers can
realize the environmental and economic benefits of
biogas production without the responsibility for day-
to-day operation of the system.
Figure 2. Biogas Recovery Systems in the U.S.'
i
2 Stage Mix
13
Ambient
Temperature
Covered Lagoon
Attached
Media
Includes digesters in start-up and construction stage.
Substantial Environmental
Benefits
One of the biggest challenges facing livestock producers
is managing manure and process water in a way that
reduces odor and protects environmental quality at a
reasonable cost. Biogas recovery systems will reduce
odors, protect water quality, and reduce greenhouse gas
emissions.
Odor control. Odors from anaerobically digested
manures are significantly less than odors from
conventional management systems. The primary sources
of odor from stored livestock manure are volatile organic
acids and hydrogen sulfide ( a "rotten egg" odor). In an
anaerobic digester, volatile organic compounds are
reduced to methane and carbon dioxide, which are
odorless gases. Hydrogen sulfide is captured with the
collected biogas and is destroyed during combustion.
Water quality protection. Anaerobic digestion provides
several water quality benefits. Digesters, particularly
heated digesters, can destroy more than 90 percent of
disease-causing bacteria that might otherwise enter
surface waters and pose a risk to human and animal
health. Digesters also reduce chemical oxygen demand
(COD). COD is one measure of the potential for
organic wastes to reduce dissolved oxygen in natural
waters. Because fish and other aquatic organisms need
minimum levels of dissolved oxygen for survival, farm
practices that reduce COD protect the health of aquatic
ecosystems.
The Natural Resources Conservation Service of the U.S. Department of Agriculture has established practice standards for ambient temperature anaerobic
digesters (Code 365) and controlled temperature anaerobic digesters (Code 366).
-------
Greenhouse gas reductions. Digesters also
reduce emissions that contribute to global
climate change. Methane is a potent
greenhouse gas with a heat trapping capacity
of approximately 21 times that of carbon
dioxide. Livestock and poultry manure emit 7
percent of annual U.S. methane emissions,
and most of that 7 percent comes from swine
and dairy operations. Biogas recovery systems
capture and combust methane, thus reducing
virtually all of the methane that otherwise
would be emitted. As shown in Figure 3,
installing digesters at dairy and swine
operations where it is economically feasible
would reduce methane emissions by 1.3
million tons per year (about 66 percent reduction from
these operations). Biogas also is a renewable form of
energy. The use of biogas to generate electricity provides
the added environmental benefit of reducing fossil fuel use
on the electric power grid, which in turn lowers emissions
of carbon dioxide, another critical greenhouse gas.
Identifying Profitable Systems
Biogas recovery systems are potentially profitable for
about 6,000 large dairy and swine facilities in the U.S.
Figure 3. Significant Methane
Emission Reductions
Animal Sector
Swine
Dairy
Total
2002 Methane
Emissions
(000 tons/year)
1,097
918
2,015
Potential Methane
Emission Reduction'
(000 tons/year)
772 (70%)
573 (62%)
1,345 (66%)
Estimates are based on installing biogas recovery systems at all feasible
operations, as defined in Figure 4.
Figure 4. Characteristics of Dairy and Swine Farms
Where Biogas Recovery Systems May be Profitable
Animal Type
Manure
Management
Method'
Size of
Operation
Dairy
Flushed or scraped
freestall barns and
dry lots
>500 head
Swine
Houses with flush,
pit recharge, or pull-
plug pit systems2
>2,000 head
These facilities are the larger operations that use liquid or
slurry manure handling systems and collect manure from
animal confinement areas frequently (Figure 4).
Profitability depends on the ability to recover the capital
and operating costs at a reasonable rate of return, and
generate a long-term income stream. Experience has
shown that the profitability of biogas systems depends on
the size of the operation, the method of manure
management, and local energy costs.
Size of operation. Available data indicate
that the unit costs for construction and
operation decrease significantly as biogas
system size increases. The potential for a
positive financial return appears to be most
likely at dairy operations with milking herds
of more than 500 cows and swine operations
with more than 2,000 head of confinement
capacity. While these farm sizes provide a
general guideline, the feasibility at individual
operations depends on a number of local
factors, including construction costs, energy
prices, and farm management practices.
1 Total solids content < 15% and at least weekly manure collection.
2 Biogas systems are not currently used at swine confinement houses with
deep pits. Deep pits under slatted floors are commonly used in cool
regions such as the upper Midwest. Deep pit systems would need to be
modified to remove manure more frequently (weekly or more often)
before a biogas utilization system could be installed.The feasibility of
conversion depends on the value of the biogas produced relative to the
capital investment required. Estimates in this report assume that deep pit
operations with more than 5,000 head could use biogas systems by
converting to at least weekly manure removal.
Manure Management Method. Current
digester systems are designed for manure that
is handled in a liquid, slurry, or semi-solid
state (Figure 5). Collection frequency also
influences the feasibility of biogas recovery
systems. Manure that is collected frequently
(i.e., at least weekly) minimizes the loss of the
-------
Figure 5. Manure Handling Practices
Affect the Feasibility and Choice of Biogas
Digester Systems
Total Solids (%)
10 15 20 25
30
„ Water Added Bedding Added
Manure ' ' ' —
Biogas Production | Recommended | Not Recommended
Digester Type Cwered Complele
_agoon or Mix
biodegradable organic matter that will be converted into
biogas. Confined swine and dairy operations typically
remove manure as frequently as every few hours to every
few days. In other animal sectors (e.g., poultry and beef
operations), manure typically may be collected no more
than 3 to 4 times per year.
Energy costs. The value of methane depends on the
energy costs avoided (e.g., electricity, fuel oil, propane).
Typically, biogas is used to generate electricity for on-site
use with any excess sold to the local electric utility. This
methane use strategy provides four possible sources of
income:
Avoided cost of electricity. The cost savings from
electricity not purchased depends on local electricity
rates. Because the total revenue derived from biogas
use depends heavily on the value of electricity,
relatively modest changes in rates can result in
significant changes in the size of operation that will be
profitable.
Sale of excess electricity to the local public utility.
There is significant variation from state to state in the
prices that utilities will pay small power producers.
Rates can be very attractive in states with net metering,
green power markets, or green pricing programs.
Waste heat recovery. Waste heat from engine-generator
sets can be recovered and used for space and water
heating, thus reducing fuel oil or propane costs.
• Greenhouse gas markets. An emerging
source of income is the sale of "carbon
credits" through brokerage houses to global
greenhouse gas markets. Several dairies have
begun receiving payments for combusting
methane from biogas recovery systems, and
more dairies are beginning to enroll in
carbon credit programs.
Candidate farms for installing biogas recovery
systems were identified using the
characteristics described in Figure 4. These
characteristics were selected based on AgSTAR
evaluations of the technical and economic
performance of successful biogas recovery
systems operating at commercial scale swine
and dairy farms. These criteria were not based
on a cost analysis. The methodology for
identifying candidate farms and estimating the
energy production potential is explained in the
appendix.
Energy Production Potential
Nationally, swine and dairy operations could generate 6.3
million MWh of electricity each year - equivalent to 722
MW of electrical grid
capacity. According to
the U.S. Department
of Energy, the average
price of electricity was
about 8 cents per
kilowatt-hour in 2004.
Using this rate, swine
and dairy operations collectively could potentially
generate electricity worth more than $500 million
annually.
State profiles at the end of
this guide characterize the
market potential in the top
ten swine and dairy states
with the greatest potential for
biogas recovery.
The number of dairy and swine farms with the potential
to recover methane for a profit varies significantly from
state to state. Figure 6 identifies the 10 states with the
greatest electrical generating potential from swine and
dairy operations. For swine, the top 10 states hold 85
percent of the electric generating potential. North
Carolina and Iowa, the largest pork producing states,
each account for more than 20 percent of the total. For
dairies, the top 10 states hold 80 percent of the potential,
with California alone accounting for almost 40 percent.
-------
Figure 6. Top 10 States for Electricity Production from
Dairy and Swine Manure
State
SWINE FARMS
NORTH CAROLINA
IOWA
MINNESOTA
OKLAHOMA
ILLINOIS
MISSOURI
INDIANA
NEBRASKA
KANSAS
TEXAS
Remaining 40 States
Subtotal
DAIRY FARMS
CALIFORNIA
IDAHO
NEW MEXICO
TEXAS
WISCONSIN
NEW YORK
ARIZONA
WASHINGTON
MICHIGAN
MINNESOTA
Remaining 40 States
Subtotal
U.S. Total
Number of
Candidate
Farms
1,179
1,022
429
52
267
200
234
148
91
13
646
4,281
963
185
123
149
175
157
73
122
72
60
544
2,623
6,904
Methane
Emissions
Reduction
(000 Tons)
247
126
40
54
36
53
28
25
29
21
113
773
263
61
62
32
8
6
35
22
6
3
75
573
1,346
Methane
Production
Potential
(billion
ftVyear)
11.5
10.2
3.5
2.9
2.8
2.7
2.2
2.0
1.6
I.I
7.3
48
18.1
4.0
3.9
2.3
2.1
2.0
1.9
1.9
1.9
0.7
9.4
48
96
Electricity
Generation
Potential
(000 MWh/year)
766
677
234
196
184
177
145
134
109
75
487
3,184
1203
267
259
154
138
132
126
126
73
46
624
3,148
6,332
Note: The procedure for estimating the energy generation potential is explained in the appendix.
-------
The pattern of regional concentration has been driven by
three main factors:
• Business practices. Vertical integration, especially in
the swine industry, has led to significant geographic
concentration. At the same time, economies of scale
have led to increasingly larger but fewer operations
over time.
• State policies. In some states, policies have encouraged
the growth of animal agriculture either for rural
economic development or to replace the loss of other
agricultural sectors.
• Climate. Favorable climate, which reduces the cost of
feed, housing, and energy, has led to some migration
to warm climates. Mild climates also lead to more
methane generation in anaerobic lagoons.
The U.S. Department of Agriculture confirms the trend
toward fewer but larger dairy and swine operations.
Larger operations emit more methane because they tend
to use more liquid manure handling systems and more
anaerobic lagoons. As a result of this trend, methane
emissions and energy generation potential are increasing
at a faster rate than the growth in animal population.
About AgSTAR
AgSTAR is an outreach and educational program that
promotes the recovery and use of methane from animal
manure. AgSTAR is one of the many voluntary initiatives
developed under the United Nations Framework
Convention on Climate Change to reduce greenhouse
gases. The program provides technical support, compiles
and distributes information, and maintains the AgSTAR
hotline to facilitate the development of commercial
systems. AgSTAR has supported development of
standards for anaerobic digestion systems and created
project development tools such as the AgSTAR
Handbook and FarmWare (a software tool for pre-
feasibility assessment of aerobic digestion).
ENERGY AND POLLUTION PREVENTION
For more information about methane
recovery technologies, contact an
AgSTAR representative at:
1-800-95AgSTAR (1-800-952-4782)
(Hours of Operation: 9:00am to
5:00pm EST)
www.epa.gov/agstar
-------
State Profiles
-------
North Carolina
Swine
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Swine Operations
Total number of mature swine (000 head)
Number of feasible swine operations'
Number of mature swine at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
2,542
9,900
1,179
9,358
247
11.5
766
1 Anaerobic digestion was considered feasible at all existing operations
with flush, pit recharge, or pull-plug pit systems with more than 2,000
swine; and at deep pit systems with more than 5,000 swine.
Farm Size
2000-4999
head
21%
Percentage of Swine Population
Swine Population (number of head)
Manure Management System
Light < 2000 J Medium 2000 - 5000 || Dark > 5000
Percentage of Manure Managed
-------
Iowa
Swine
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Swine Operations
Total number of mature swine (000 head)
Number of feasible swine operations'
Number of mature swine at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production
Electricity generation
potential (billion ftVyear)
potential (000 MWh/year)
10,205
15,450
1,022
7,900
126
10.2
677
1 Anaerobic digestion was considered feasible at all existing operations
with flush, pit recharge, or pull-plug pit systems with more than 2,000
swine; and at deep pit systems with more than 5,000 swine.
Farm Size
Percentage of Swine Population
Swine Population (number of head)
Manure Management System
| Light < 2000 J Medium 2000 - 5000 || Dark > 5000
Percentage of Manure Managed
Pasture
1%
-------
Minnesota
Swine
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Swine Operations
Total number of mature swine (000 head)
Number of feasible swine operations'
Number of mature swine at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
5,628
6,050
429
3,083
40
3.5
234
1 Anaerobic digestion was considered feasible at all existing operations
with flush, pit recharge, or pull-plug pit systems with more than 2,000
swine; and at deep pit systems with more than 5,000 swine.
Farm Size
Percentage of Swine Population
Swine Population (number of head)
Manure Management System
Pasture
0%
Percentage of Manure Managed
| Light < 2000 J Medium 2000 - 5000 || Dark > 5000
10
-------
Oklahoma
Swine
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Swine Operations
Total number of mature swine (000 head)
Number of feasible swine operations'
Number of mature swine at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
2,49 1
2,368
52
2,099
54
2.9
196
1 Anaerobic digestion was considered feasible at all existing operations
with flush, pit recharge, or pull-plug pit systems with more than 2,000
swine; and at deep pit systems with more than 5,000 swine.
Swine Population (number of head)
I Light < 2000 n Medium 2000 - 5000 Q Dark > 5000
Farm Size
Percentage of Swine Population
Manure Management System
Pasture
1%
Percentage of Manure Managed
11
-------
Illinois
Swine
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Swine Operations
Total number of mature swine (000 head)
Number of feasible swine operations'
Number of mature swine at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
3,929
4,225
267
2,076
36
2.8
184
1 Anaerobic digestion was considered feasible at all existing operations
with flush, pit recharge, or pull-plug pit systems with more than 2,000
swine; and at deep pit systems with more than 5,000 swine.
Farm Size
Percentage of Swine Population
Swine Population (number of head)
Manure Management System
Percentage of Manure Managed
| Light < 2000 _] Medium 2000 - 5000 || Dark > 5000
12
-------
Missouri
Swine
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Swine Operations
Total number of mature swine (000 head)
Number of feasible swine operations'
Number of mature swine at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
3,449
2,938
200
2,189
53
2.7
177
1 Anaerobic digestion was considered feasible at all existing operations
with flush, pit recharge, or pull-plug pit systems with more than 2,000
swine; and at deep pit systems with more than 5,000 swine.
Farm Size
Percentage of Swine Population
Swine Population (number of head)
Manure Management System
Pasture
Deep Pit \ 0%
14%
Percentage of Manure Managed
Light < 2000 J Medium 2000 - 5000 || Dark > 5000
13
-------
Indiana
Swine
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Swine Operations
Total number of mature swine (000 head)
Number of feasible swine operations'
Number of mature swine at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
4,087
3,213
234
1,829
28
2.2
145
1 Anaerobic digestion was considered feasible at all existing operations
with flush, pit recharge, or pull-plug pit systems with more than 2,000
swine; and at deep pit systems with more than 5,000 swine.
Farm Size
Percentage of Swine Population
Swine Population (number of head)
Manure Management System
Pasture
1%
Percentage of Manure Managed
Light < 2000 J Medium 2000 - 5000 || Dark > 5000
14
-------
Nebraska
Swine
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Swine Operations
Total number of mature swine (000 head)
Number of feasible swine operations'
Number of mature swine at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
3,075
2,963
148
1,579
25
2.0
134
1 Anaerobic digestion was considered feasible at all existing operations
with flush, pit recharge, or pull-plug pit systems with more than 2,000
swine; and at deep pit systems with more than 5,000 swine.
Swine Population (number of head)
I Light < 2000 n Medium 2000 - 5000 Q Dark > 5000
Farm Size
Percentage of Swine Population
Manure Management System
Pasture
1%
Percentage of Manure Managed
15
-------
Kansas
Swine
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Swine Operations
Total number of mature swine (000 head)
Number of feasible swine operations'
Number of mature swine at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
1,648
1,565
91
1,192
29
1.6
109
1 Anaerobic digestion was considered feasible at all existing operations
with flush, pit recharge, or pull-plug pit systems with more than 2,000
swine; and at deep pit systems with more than 5,000 swine.
Farm Size
Percentage of Swine Population
Swine Population (number of head)
Light < 2000 J Medium 2000 - 5000 || Dark > 5000
Manure Management System
Pasture
3%
Percentage of Manure Managed
16
-------
Texas
Swine
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Swine Operations
Total number of mature swine (000 head)
Number of feasible swine operations'
Number of mature swine at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
4,671
958
13
845
21
I.I
75
1 Anaerobic digestion was considered feasible at all existing operations
with flush, pit recharge, or pull-plug pit systems with more than 2,000
swine; and at deep pit systems with more than 5,000 swine.
2000-4999
head
1%
Farm Size
Percentage of Swine Population
Swine Population (number of head)
Manure Management System
Pasture
2%
Percentage of Manure Managed
Light < 2000 J Medium 2000 - 5000 || Dark > 5000
17
-------
California
Dairy
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Dairy Operations
Total number of mature dairy cows (000 head)
Number of feasible dairy cow operations'
Number of mature dairy cows at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
2,793
1,624
963
1,286
263
18.1
1,203
Farm Size
Percentage of Dairy Cow Population
'Anaerobic digestion was considered feasible at all existing operations
with liquid manure systems and more than 500 dairy cows.
Dairy Cow Population (number of head) Manure Management System
Liquid/
Slurry Storage
21%
Deep Pit
0%
Percentage of Manure Managed
| Light < 500 J Medium 500 - 1000 | Dark > 1000
18
-------
Idaho
Dairy
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Dairy Operations
Total number of mature dairy cows (000 head)
Number of feasible dairy cow operations'
Number of mature dairy cows at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
982
378
185
285
61
4.0
267
200-500
head
11%
Farm Size
Percentage of Dairy Cow Population
'Anaerobic digestion was considered feasible at all existing operations
with liquid manure systems and more than 500 dairy cows.
Dairy Cow Population (number of head) Manure Management System
Deep Pit
1%
Liquid/
Slurry Storage
23%
Pasture
0%
Percentage of Manure Managed
Light < 500 J Medium 500 - 1000 J Dark > 1000
19
-------
New Mexico
Dairy
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Dairy Operations
Total number of mature dairy cows (000 head)
Number of feasible dairy cow operations'
Number of mature dairy cows at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
377
291
123
276
62
3.9
259
Farm Size
Percentage of Dairy Cow Population
'Anaerobic digestion was considered feasible at all existing operations
with liquid manure systems and more than 500 dairy cows.
Dairy Cow Population (number of head) Manure Management System
Anaerobic
Lagoon
62%
Liquid/
Slurry Storage
19%
Deep Pit
0%
Percentage of Manure Managed
| Light < 500 _| Medium 500 - 1000 | Dark > 1000
20
-------
Texas
Dairy
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Dairy Operations
Total number of mature dairy cows (000 head)
Number of feasible dairy cow operations'
Number of mature dairy cows at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
2,080
316
149
165
32
2.3
154
Farm Size
Percentage of Dairy Cow Population
'Anaerobic digestion was considered feasible at all existing operations
with liquid manure systems and more than 500 dairy cows.
Dairy Cow Population (number of head) Manure Management System
Liquid/
Slurry Storage
24%
Deep Pit
2%
Spread/ Pasture
Solid \^ 8% / 0%
Storage
13%
Percentage of Manure Managed
| Light < 500 _| Medium 500 - 1000 | Dark > 1000
21
-------
Wisconsin
Dairy
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Dairy Operations
Total number of mature dairy cows (000 head)
Number of feasible dairy cow operations'
Number of mature dairy cows at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
1 6,886
1,283
175
148
8
2.1
138
Farm Size
Percentage of Dairy Cow Population
'Anaerobic digestion was considered feasible at all existing operations
with liquid manure systems and more than 500 dairy cows.
Dairy Cow Population (number of head) Manure Management System
Deep Pit
4%
Liquid/
Slurry Storage
24%
Percentage of Manure Managed
| Light < 500 J Medium 500 - 1000 J Dark > 1000
22
-------
New York
Dairy
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Dairy Operations
Total number of mature dairy cows (000 head)
Number of feasible dairy cow operations'
Number of mature dairy cows at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
7,388
677
157
141
6
2.0
132
Farm Size
Percentage of Dairy Cow Population
'Anaerobic digestion was considered feasible at all existing operations
with liquid manure systems and more than 500 dairy cows.
Dairy Cow Population (number of head) Manure Management System
Liquid/
Slurry Storage
16%
Anaerobic
Lagoon
10%
Deep Pit
2%
Percentage of Manure Managed
Light < 500 J Medium 500 - 1000 | Dark > 1000
23
-------
Arizona
Dairy
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Dairy Operations
Total number of mature dairy cows (000 head)
Number of feasible dairy cow operations'
Number of mature dairy cows at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
274
140
73
135
35
1.9
126
Farm Size
200-500
head
2%
Percentage of Dairy Cow Population
'Anaerobic digestion was considered feasible at all existing operations
with liquid manure systems and more than 500 dairy cows.
Dairy Cow Population (number of head) Manure Management System
Liquid/
Slurry Storage
20%
Deep Pit
0%
Pasture
0%
Percentage of Manure Managed
| Light < 500 J Medium 500 - 1000 | Dark > 1000
24
-------
Washington
Dairy
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Dairy Operations
Total number of mature dairy cows (000 head)
Number of feasible dairy cow operations'
Number of mature dairy cows at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
1,208
248
122
135
22
1.9
126
Farm Size
Percentage of Dairy Cow Population
'Anaerobic digestion was considered feasible at all existing operations
with liquid manure systems and more than 500 dairy cows.
Dairy Cow Population (number of head) Manure Management System
Light < 500 J Medium 500 - 1000 J Dark > 1000
Deep Pit
1%
Liquid/
Slurry Storage
22%
Percentage of Manure Managed
25
-------
Michigan
Dairy
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Dairy Operations
Total number of mature dairy cows (000 head)
Number of feasible dairy cow operations'
Number of mature dairy cows at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
3,013
300
72
78
6
I.I
73
Farm Size
Percentage of Dairy Cow Population
'Anaerobic digestion was considered feasible at all existing operations
with liquid manure systems and more than 500 dairy cows.
Dairy Cow Population (number of head) Manure Management System
Liquid/
Slurry Storage
33%
Deep Pit
— 4%
Pasture
3%
Daily
Spread
10%
Percentage of Manure Managed
| Light < 500 J Medium 500 - 1000 | Dark > 1000
26
-------
Minnesota
Dairy
Market Opportunities to Generate
Electricity with Anaerobic Digestion (2002)
Total Number of Dairy Operations
Total number of mature dairy cows (000 head)
Number of feasible dairy cow operations'
Number of mature dairy cows at feasible
systems (000 head)
Methane emission reduction potential (000
tons/year)
Methane production potential (billion ftVyear)
Electricity generation potential (000 MWh/year)
6,474
501
60
49
3
0.7
46
Farm Size
Percentage of Dairy Cow Population
'Anaerobic digestion was considered feasible at all existing operations
with liquid manure systems and more than 500 dairy cows.
Dairy Cow Population (number of head) Manure Management System
Liquid/
Slurry Storage
24%
Deep Pit
5%
Pasture
6%
Percentage of Manure Managed
| Light < 500 J Medium 500 - 1000 | Dark > 1000
27
-------
-------
Appendix: Methodology
29
-------
General Methodology
This section describes the methodology used to estimate the maximum potential for U.S. swine and dairy operations
to generate electricity from biogas. The general approach was to:
liry animal populations and profiles of farm sizes by state. These data were taken from
published USDA reports.
• Estimate the distribution of manure management practices by state. These distributions were derived from USDA-
supplied data and observations by EPA.
• Estimate the animal populations on farms where biogas systems are feasible. The criteria described in Figure 4 was used.
• Estimate baseline methane emissions and emission reductions from the candidate farms. Methane emissions were
estimated using EPA's greenhouse gas inventory methodology. When farms convert to a biogas recovery system, the
methane emission reduction is essentially 100 percent of baseline emissions.
• Estimate the biogas production and electricity generating potential. These estimates were based on values reported in
the literature and AgSTAR evaluations.
A more detailed discussion of these steps, including data sources and calculation methodology, is presented below.
State Animal Populations and Farm Profiles
The potential to reduce methane emissions from dairy and swine manures was based on estimates of the number of
milk cows that have calved and the number of hogs and pigs in each state in 2002. The estimates were based on
inventory estimates issued by the USDA National Agricultural Statistics Service (NASS). The full methodology for
estimating dairy and swine populations can be found in the Inventory for U.S. Greenhouse Gas Emissions and Sinks:
1990- 2002 (USEPA, 2002)
In January of each year, NASS presents estimates of the number of dairy operations in each of the 29 leading dairy
states by size. These data were used in conjunction with farm size data from the 2002 Census of Agriculture (USDA,
2002) to estimate the number of operations with milking herds of specified sizes and the number of cows at these
operations. This methodology was also used to estimate the number of swine operations in each state with a
confinement capacity of 2,000 or more head and the number of hogs and pigs confined on these operations.
Manure Management Practices
Manure management practices for dairy and swine operations were determined using data from USDA's 2002 Census
of Agriculture, USDA's National Animal Health Monitoring System (NAHMS), EPA's Office of Water, and expert
sources.
For dairy operations, the distribution of manure production by waste management system for farms with more than
200 head was estimated using data from the EPA Office of Water. The methods of manure management for medium
(200 to 500 head) and large (more than 500 head) farms and the percent of farms that use each type of system (by
geographic region) were used to estimate the percent of manure managed in each type of system. Manure
management estimates for small (less than 200 head) dairies were obtained from NAHMS Dairy '96 data.
Information regarding the state distribution of daily spread and outdoor confinement (pasture, range, and paddock)
operations for dairy cattle was obtained from personal communication with personnel from state Natural Resource
Conservation Service offices, state universities, NASS, and other experts.
For swine operations, the distribution of manure production by waste management system was estimated using
USDA data broken out by geographic region and farm size. Manure management information for medium (200 to
2,000 head) and large (greater than 2,000 head) farms was obtained from USDA NAHMS Swine 2000 data. It was
assumed that operations with less than 200 head were outdoor confinement operations.
30
-------
Methane Emissions
Methane emissions were estimated based on the methodologies used for the Inventory of U.S. Greenhouse Gas
Emissions and Sinks: 1990-2002 (USEPA, 2004). These methodologies were developed by the International Panel on
Climate Change (IPCC) and presented in Good Practice Guidance and Uncertainty Management in National
Greenhouse Gas Inventories (IPCC, 2000).
Methane emission estimates were developed for each state and animal group using the equation presented in Figure 7-
A sample calculation for two types of manure management systems is shown in Figure 8. For swine, total volatile
solids (VS) was calculated using a national average VS excretion rate from the Agricultural Waste Management Field
Handbook (USDA, 1992), which was multiplied by the average weight (TAM) of the animal and the State-specific
animal population. For dairy cattle, regional VS excretion rates that are related to the diet of the animal were used
(Peterson et al., 2002).
Methane conversion factors (MCFs) were determined for each type of manure management system. For dry systems,
the default IPCC factors were used. MCFs for liquid/slurry, anaerobic lagoon, and deep pit systems were calculated
based on the forecast performance of biological systems relative to temperature changes as predicted in the van't Hoff-
Arrhenius equation. The MCF calculations model the average monthly ambient temperature, a minimum system
temperature, the carryover of volatile solids in the system from month to month, and a factor to account for
management and design practices that result in the loss of volatile solids from lagoon systems. Methane conversion
factors for each state are shown in Figure 9-
Figure 7. Methane Emissions Equation
Methane Emissions = Population xTAM xVS x MCF x B0
where:
Population = 2002 state animal population
TAM = Typical animal mass, Ib
VS = Total volatile solids excretion rate, lbVS/1,000 Ib live weight-day
MCF = Methane conversion factor, percent
B0 = Maximum methane producing capacity, ft3 ChL/lb total volatile solids
For dairy cows, B0 = 3.84 (Morris, 1976)
For swine, B0 = 7.69 (Hashimoto, 1984)
Biogas Production and Electricity Generating Potential
The estimates of the biogas production potential from dairy cow and swine manures presented in this report are
based on the following approach:
• For swine manure, evaluations of the performance of a covered lagoon and a mesophilic, intermittently mixed
digester suggest that both systems provide approximately the same degree of total VS reduction, 45 percent
(Martin, 2002, 2003). In addition, the methane yield for both systems was similar and averaged 12 ft3 per Ib of VS
destroyed This value is within the reported range of values for methane production from municipal wastewater
treatment biosolids).
• For dairy manure, results from two studies indicate that mesophilic plug-flow digesters with a 20-day hydraulic
residence time (HRT) produce between 38 and 39 ft3 of methane per cow-day (Jewell et al., 1981; Martin, 2004).
For this report, a value of 38.5 ft3 methane per cow per day was used. Although actual HRTs may vary, a 20-day
HRT is the standard design value.
31
-------
• To calculate the energy content of biogas produced in swine and dairy digesters, a heating value of 1,010 BTUs per
ft3 methane was used.
• Based on performance data for engine-generator sets obtained from Caterpillar, Inc., it has been suggested that the
maximum thermal conversion efficiency of biogas to electricity is 28.5 percent (Koelsch and Walker, 1981).
However, sizing biogas fueled engine-generator sets to operate at maximum output is difficult, and these units
cannot be operated 100 percent of the time due to maintenance and repairs. Accordingly, a thermal conversion
efficiency of 25 percent and an on-line operating rate of 90 percent was used. Based on these factors, electrical
output was estimated at 66.6 kWh per 1,000 ft3 of methane.
References
Hashimoto, A.G. 1984. Methane from Swine Manure: Effect of Temperature and Influent Substrate Concentration on
Kinetic Parameter (K). Agricultural Wastes 9 (1984):299-308.
IPCC. 2000. Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories, ]. Penman,
D. Kruger, I. Galbally, T. Hiraishi, B. Nyenzi, S. Emmanul, L. Bundia, R. Hoppaus, T. Martinsen, J. Meijer, K.
Miwa, and K. Tanabe (Eds). Institute for Global Strategies, Japan.
Jewell, WJ., R.M. Kabrick, S. Dell'Orto, K.J. Fanfoni, and R.J. Cummings. 1981. Earthen-Supported Plug Flow
Reactor for Dairy Operations. In: Methane Technology for Agriculture, NRAES -13- Northeast Regional Agricultural
Engineering Service, Cornell University, Ithaca, New York. pp. 1-24.
Koelsch, R., and L.P.Walker. 1981. Matching Dairy Farm Energy Use and Biogas Production. In: Methane Technology
for Agriculture, NRAES-13- Northeast Regional Agricultural Engineering Service, Cornell University, Ithaca, New
York. pp. 114-136.
Martin, J.H., Jr. 2002. A Comparison of the Performance of Three Swine Waste Stabilization Systems. Final report
submitted to the U.S. Environmental Protection Agency AgSTAR Program by Eastern Research Group, Inc., Boston,
Massachusetts.
Martin, J.H., Jr. 2003- An Assessment of the Performance of the Colorado Pork, LLC, Anaerobic Digestion and Biogas
Utilization System. Final report submitted to the U.S. Environmental Protection Agency AgSTAR Program by Eastern
Research Group, Inc., Boston, Massachusetts.
Martin, J.H., Jr. 2004. A Comparison of Dairy Cattle Manure Management With and Without Anaerobic Digestion and
Biogas Utilization. Final report submitted to the U.S. Environmental Protection Agency AgSTAR Program by Eastern
Research Group, Inc., Boston, Massachusetts.
Morris, G. R. 197'6. Anaerobic Fermentation of Animal Wastes: A Kinetic and Empirical Design Evaluation.
Unpublished M.S. Thesis, Cornell University, Ithaca, New York.
Peterson, K., J. King, and D. Johnson. 2002. Methodology and Results from Revised Diet Characterization Analysis.
Memorandum to EPA from ICF Consulting under contract no. 68-W7-0069, task order 505-01.
US DA. 1992. AgriculturalWaste Management Field Handbook, revised July 1996. Natural Resources Conservation
Service, Washington, DC.
USDA. 2004. 2002 Census of Agriculture. National Agricultural Statistics Service, Washington, DC.
USEPA. 2004. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2002. Report No. EPA 430-R-02-003-
Office of Atmospheric Programs, Washington, DC.
32
-------
Figure S. Example Calculations: Impacts of a
Biogas Recovery System Replacing a Manure Storage
Facility and a Conventional Anaerobic Lagoon
Factors
Manure storage
tank or pond
Conventional
anaerobic lagoon
Methane emission reductions
Number of cows
Average live weight, Ib/cow
Total volatile solids (VS) excretion rate, Ib/ 1,000 Ib live weight-day
B0,ft3/lbVS
MCF1, decimal
Methane density, Ib/ft3
Methane emissions2, tons/yr
Methane emission reduction from biogas capture and utilization3, ton/yr
Equivalent reduction in carbon dioxide emissions4, tons/yr
500
1,400
8.5
3.84
0.292
0.041
50
50
1,048
500
1,400
8.5
3.84
0.707
0.041
121
121
2,538
Displaced emissions from utility electric generation
Methane production, ft3/yr @ 38.5 ft3/cow-day
Electricity generation potential5, kWh/yr
Reduction in utility carbon dioxide emissions6, tons/yr
Total greenhouse gas emission reductions as carbon dioxide, tons/yr
7,026,250
467,838
526
1,574
7,026,250
467,838
526
3,064
1 U.S. average MCF for manure storage tanks and ponds, and conventional anaerobic lagoons.
2 Methane emissions = number of cows * average live weight *VS excretion rate * I/I000 * B0 * MCF * methane density *
365 days/yr * ton/2000lb.
3 Biogas combustion destroys essentially 100 percent of baseline methane emissions.
4 Methane has approximately 21 times the heat trapping capacity of carbon dioxide.
5 Generation, kWh/yr = methane production * 1,010 Btu/ft3 of methane * kWh/3,41 3 Btu * 0.25 (methane to electricity
conversion efficiency) * 0.9 (on-line efficiency).
'Assuming 2,249 Ib of carbon dioxide emitted per MWh generated from coal (Spath et al., 1999).
33
-------
Figure 9. Methane Conversion Factors by State for 2003 (percent)
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Storage
Tank or Pond
38.5
13.8
44.8
36.1
37.7
22.2
23.9
29.7
52.2
38.3
59.7
23.2
26.9
26.0
24.7
31.9
30.4
46.1
19.5
27.6
23.2
22.0
22.8
40.1
30.4
Anaerobic
Lagoon
75.8
48.3
79.3
65.0
76.2
66.7
69.4
73.9
77.8
75.6
77.1
68.3
71.5
70.6
69.7
74.5
73.2
77.2
63.3
72.1
68.7
66.7
67.9
76.1
73.8
State
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Storage
Tank or Pond
21.1
26.7
25.7
21.0
26.4
32.6
21.7
33.7
21.7
24.8
36.5
22.8
25.2
24.6
37.8
24.2
32.6
41.6
26.2
20.2
27.9
23.4
25.3
22.4
21.3
Anaerobic
Lagoon
65.9
71.5
70.5
65.5
71.9
74.4
66.6
74.4
66.9
69.5
76.1
67.0
70.4
70.4
75.8
69.6
74.2
77.0
71.1
64.5
72.0
67.9
69.8
67.7
66.0
: From Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2003 (EPA 430-R-O5-003).
34
-------
-------
------- |