Market Opportunities for STAR

Biogas Recovery Systems 

at U.S. Livestock Facilities

December 2010

Contents

i

Substantial Environmental Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Economic Benefits of Biogas Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Identifying Profitable Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Energy Production Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Top Ten States for Energy Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Biogas from Poultry Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Appendix A: Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

Appendix B: Profiles of Top Ten Swine and Dairy States with

Biogas Energy Recovery Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1
1

Biogas is a valuable by-product of 

decomposing animal waste in livestock 

operations. It is produced when the 

organic fraction of manure decomposes 

anaerobically (i.e., in the absence of 

oxygen). Biogas typically contains 60 

to 70 percent methane, the primary 

constituent of natural gas. Biogas 

recovery systems at livestock operations 

can be a cost-effective source of clean, 

renewable energy that reduces greenhouse gas emissions. 

The greatest potential for implementing a successful biogas capture and use project is when 

manure is collected as a liquid, slurry, or semi-solid and stored in open pits, ponds, or lagoons. 

Because the vast majority of large dairy and swine operations in the United States use liquid or 

slurry manure management systems, biogas production potential at these operations is high, as 

are the potential greenhouse gas reductions if biogas recovery systems are implemented. Other 

animal sectors, including poultry farms and beef lots, manage manure primarily in solid form, and 

efforts to more effectively produce renewable energy from these management systems are also 

being developed. 

Biogas can be collected from manure and burned to supply on-farm energy needs for electricity, 

heating, cooling, or other energy needs. Surplus electricity or biogas can also be sold to neighboring operations or the utility grid. As of November 2010, AgSTAR estimated that 160 manure 

anaerobic digester biogas recovery systems were in operation at commercial livestock facilities in 

the United States. The full potential to provide renewable energy is much greater, however, with an 

estimated 8,200 U.S. dairy and swine operations (Table 1) that could support biogas recovery systems. Additionally, biogas recovery systems may be feasible at some poultry and beef lot operations as new and improved technologies for these manual types enter the market. 

Substantial Environmental Benefits

One of the biggest challenges facing livestock producers is managing the large amount of animal 

waste (e.g., manure, process water) produced by their operations. Biogas recovery systems offer a 

number of air and water quality benefits for managing these wastes, including:

Odor control: Odors from anaerobically digested manures are significantly reduced as compared 

to odors from conventional storage and land application systems. The primary sources of odor 

from stored livestock manure are volatile organic acids and hydrogen sulfide (i.e., “rotten egg” 

odor). In an anaerobic digester, volatile organic compounds are reduced to methane and carbon 

dioxide, which are odorless gases. The volatized fraction of hydrogen sulfide is captured with the 

collected biogas and is destroyed during combustion. 

Table 1. Potential for Biogas Recovery Systems at Swine and 

Dairy Operations

Animal 

Sector 

Candidate 

Farms

Energy Generating Potential

MW MWh/year Thousands of 

MMBtu/year

Swine 5,596 804 6,341,527 68,710

Dairy 2,645 863 6,802,914 73,709

Total 8,241 1,667 13,144,441 142,419
2

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 biological oxygen demand 

(BOD). BOD 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 BOD protect the 

health of aquatic ecosystems.

Greenhouse gas reduction: Digesters 

reduce emissions that contribute to global 

climate change. Methane currently contributes one-third of all man-made climate 

forcing and is a potent greenhouse gas 

with a global warming potential approximately 21 times that of carbon dioxide. 

In 2007, EPA estimated that livestock and 

poultry manure emitted almost 8 percent of annual U.S. methane emissions; the majority of those 

manure emissions came from swine and dairy operations. Biogas recovery systems capture and 

combust methane, reducing virtually all of the methane that otherwise would be emitted. As 

shown in Figure 1, installing digesters at dairy and swine operations where it is feasible would 

reduce methane emissions by another 1.8 million tons per year (representing approximately an 87 

percent reduction from these operations). 

Biogas can be used as a renewable source of energy. The use of biogas to generate energy 

can provide the added environmental benefit of offsetting fossil fuel use, which in turn lowers 

emissions of carbon dioxide (CO2), another critical greenhouse gas.

Economic Benefits of Biogas Recovery

Biogas recovery systems offer substantial economic benefits, all of which improve the feasibility of 

a potential project. 

Energy use and sale: The principal economic benefit of biogas recovery is for energy use, which 

can take several different forms. One option is to use biogas as a direct fuel source for heating, 

boilers, chillers, or drying; or upgraded to a cleaner gas and put into natural gas pipelines for sale. 

Alternatively, biogas can be combusted in an engine-generator to produce electricity, which can 

then be used to power on-farm operations or sold to the electric grid. Additionally, waste heat from 

the engine-generator set can be captured in cogeneration power systems and used for heating the 

digester, or for water and space heating. All of these options offer financial benefits in the form of 

reducing energy purchases and, in some cases, direct revenue from the sale of refined biogas or 

electric power to third parties.

0 500 1,000 1,500 2,000 2,500

Swine

Dairy

Total

Methane Emissions1

(tons/year, in thousands)

Potential Methane

Emission Reductions2

(tons/year, in thousands)

Figure 1. 2007 Methane Emissions and Potential 

Reductions with Anaerobic Digesters at Feasible Swine 

and Dairy Operations

1Emissions based on 2007 values from EPA’s Inventory of U.S. 

Greenhouse Gas Emissions and Sinks: 1990-2008.

2Estimates based on installing biogas recovery systems at all 

feasible operations, as defined in Table 2.
3

Valuable by-products: Another benefit of anaerobic digestion is the variety of by-products that 

can be created from the digestate (digester effluent) solids. Examples include fertilizer, livestock 

bedding, and compost that can be used at the farm or sold. For instance, the nitrogen in manure is 

converted to a more readily available form for plants after anaerobic digestion. In comparison, manure that is treated or stored under aerobic systems (systems that expose the manure to oxygen) 

has a higher nitrogen loss as a result of conversion to ammonia and subsequent volatilization.

Renewable energy credits and greenhouse gas markets: Using biogas for energy reduces 

methane emissions (a greenhouse gas), and reduces demand for fossil fuels for heating or electricity purposes. In more than 30 states, electricity produced from biogas may qualify operations with 

a digester to receive renewable energy credits or a premium price for their green power. Another 

emerging source of income is the sale of “carbon credits” in global greenhouse gas markets. Several operations have begun receiving payments for the reduced methane emissions as a result of 

biogas recovery systems.

Identifying Profitable Systems

Candidate farms for installing biogas recovery systems were identified using the characteristics 

described in Table 2. These characteristics were selected based on AgSTAR evaluations of the technical and economic performance of successful digester systems operating on commercial scale 

swine and dairy farms. AgSTAR did not conduct a site specific cost analysis; specific sites conditions, such as energy contracts, environmental permitting requirements, and other variables will 

impact the economic feasibility of projects.

The methodology for identifying candidate farms and estimating the energy production potential is 

described in Appendix A. Although there are five operating digesters projects on poultry farms as 

of November 2010, this report did not assess candidates in this livestock sector. For further discussion of biogas production from poultry manure, please see page 7.

As shown in Table 1, biogas recovery systems are potentially profitable for more than 8,200 dairy 

and swine facilities in the United States. These facilities are large operations that use liquid or 

slurry manure handling systems, and collect manure frequently from animal confinement areas as 

described in Table 2.

Table 2. Typical Characteristics Where Biogas Recovery Systems May Be Profitability

Animal Type Dairy Swine

Manure Management 

Method1

Flushed or scraped freestall 

barns and open lots

Houses with flush, pit 

recharge, or pull-plug 

pit systems2

Size of Operation ≥ 500 head ≥ 2,000 head

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 before a biogas capture and 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.
4 2

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, operation, and maintenance 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 at least 500 cows and at swine operations with at least 2,000 total head of confinement capacity. Again, feasibility and profitability at individual operations depends on a number of 

factors, including but not limited to operation size. 

Manure management method: Current digester systems are designed for manure that is 

handled in a liquid, slurry, or semi-solid state (Figure 2). Collection frequency also influences the 

feasibility of biogas recovery systems. Manure that is collected at least weekly minimizes the loss 

of the biodegradable organic matter that is converted into biogas during storage prior to digestion. 

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 is typically 

collected no more than three to four times per year as a result of using dry manure management 

systems. 

Energy costs: The value of biogas 

depends on the price of the energy it 

replaces (e.g., electricity, fuel oil, liquefied petroleum gas (LPG)). Typically, 

biogas is used to generate electricity 

for on-site use, and any excess electricity is sold to the local electric utility. 

This strategy provides three 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 

usually depends heavily on the 

value of electricity, relatively modest changes in rates can result in a significant change in the 

size of the operation where biogas capture and utilization will be profitable.

■ Sale of excess electricity to the local 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 LPG purchases.

Figure 2. Manure Handling Practices Affect the Feasibility 

and Choice of Digester Systems

Figure 2. Manure Handling Practices Affect the Feasiblity

and Choice of Biogas Digester Systems

Water Added Manure 

Classification 

Handling Options 

Biogas Production 

Digester Type 

Bedding Added 

As Excreted 

Liquid Slurry Semi-Solid Solid 

Pump Scrape Scrape and Stack 

Recommended Not Recommended 

0 5 10 15 20 25 30 

Covered 

Lagoon or 

Attached Media 

Complete 

Mix 

Plug 

Flow 

Total Solids (%)

AgSTAR’s fact sheet Anaerobic Digestion Capital Costs 

for Dairy Farms, available at 

www.epa.gov/agstar, provides preliminary guidance 

on estimating capital costs.
5 2

Energy Production Potential

Nationally, swine and dairy operations could generate more than 13 million MWh of electricity 

each year — equivalent to more than 1,670 MW of electrical grid capacity or more than 44 million 

MMBtus1 of displaced fossil fuel use. According to the U.S. Department of Energy, the average 

price of electricity was about 10 cents per kilowatt-hour (kWh) in 2009. Using this rate, swine and 

dairy operations could potentially generate $1.3 billion annually in avoided electricity purchases.

Top 10 States for Energy Potential

The number of dairy and swine farms with the potential to recover methane varies significantly 

from state to state. Figures 3 and 4 depict the number of candidate swine and dairy farms in each 

state, respectively. 

Table 3 identifies the 10 states with the greatest electricity 

generation potential from swine and dairy operations. For 

swine, the top 10 states account for approximately 86 percent of the total electricity generation potential. Iowa and 

North Carolina, the largest pork producing states, account 

for 29 percent and 18 percent of the total, respectively. For 

dairies, the top 10 states represent 82 percent of the total 

potential, with California accounting for 35 percent.

Figure 3: Candidate Swine Farms Figure 4: Candidate Dairy Farms

0-15 16-35 36-80 81-250 251-900

Swine Candidate Farms Dairy Candidate Farms

0-15 16-35 36-80 81-250 251-900

State profiles in Appendix B 

characterize the market 

potential in the top ten 

swine and dairy states with 

the greatest potential for 

biogas recovery.

1MMBtu = 1,000,000 Btu
6 2

State

Number of

Candidate 

Farms 

Methane 

Emissions 

Reductions

(Thousand 

Tons)

Methane 

Production 

Potential

(billion ft3/

year)

Energy 

Generation 

Potential

(Thousand 

MMBtu/

year)

Electricity 

Generation 

Potential 

(Thousand 

MWh/year)

Swine Farms

Iowa 1,997 301 21.5 6,243 1,829 

North Carolina 939 203 13.2 3,826 1,121 

Minnesota 707 63 7.3 2,119 621 

Illinois 350 39 4.3 1,240 363 

Missouri 154 34 3.5 1,028 301 

Indiana 296 31 3.5 1,011 296 

Oklahoma 56 51 3.4 997 292 

Nebraska 177 27 3.2 927 272 

Kansas 80 22 2.3 681 199 

Texas 10 25 1.6 477 140 

Remaining 40 

States

 830 109 10.6 3,096 907 

Sub Total 5,596 905 74.4 21,645 6,341 

Dairy Farms

California 889 341 27.9 8,104 2,375 

Idaho 203 99 8.9 2,601 762 

New Mexico 110 64 5.3 1,553 455 

Texas 155 66 5.0 1,463 429 

Wisconsin 251 41 4.5 1,316 386 

Washington 125 35 3.4 1,003 294 

Arizona 54 44 3.1 898 263 

Michigan 107 26 2.9 838 246 

New York 111 18 2.1 603 177 

Colorado 54 22 2.0 595 174 

Remaining 40 

States

588 152 14.6 4,244 1,243 

Sub Total 2,647 908 79.7 23,218 6,804

U.S. Total 8,243 1,813 154.1 44,863 13,145

Table 3. Top 10 States for Electricity Generation from Swine and Dairy Manure

Note: The procedure for estimating the energy generation potential is explained in Appendix A.
7

Biogas from Poultry Operations

Poultry operations are classified as either producers of table eggs or birds for meat consumption, 

the latter including broiler, turkey, duck, and geese production. Most poultry operations reduce 

manure moisture content by evaporation or the addition of bedding material, or both. Dry manure 

management systems have lower potential for anaerobic digestion because the microorganisms 

that degrade the organics require moisture and the manure needs to be in a slurry state. Hence, 

poultry manure management systems often are not readily adaptable to the use of anaerobic 

digesters. However, as of November 2010, there are five operational poultry anaerobic digestion 

systems in the United States, indicating that developers can design systems to overcome the 

challenges.

The following describes typical poultry management systems:

Broilers and turkeys: The most common type of housing for meat birds is enclosed housing 

where birds are raised on litter (e.g., wood shavings, rice hulls, chopped straw, peanut hulls). 

Typically, the top layer of litter and dried manure (termed “cake”) that accumulates is removed 

between flocks (6 to 7 flocks per year are cycled through) with total removal occurring every one to 

three years. This infrequent removal cycle results in loss of a substantial amount of organic matter 

that is the source of biogas production under anaerobic conditions. In addition, the litter material 

that is mixed with the manure has little biogas production potential.

Laying hens: Although many egg producers use systems to reduce manure moisture content 

in-place, anaerobic digestion can be incorporated into some manure management systems. Typically, layers are raised in cages that are suspended above the floor to separate the layers from the 

manure.

■ High-rise manure management systems utilize two-story houses that provide long-term manure 

storage under cages located in the upper story of the house. The ventilation system is designed 

to dry the manure as it accumulates under the caged birds. Therefore, the typical high-rise cage 

system is not suitable for anaerobic digestion because the manure is too dry and the system 

is designed for long-term dry storage of manure. In most operations, liquid would have to be 

added to create a slurry form of manure.

■ Scrape, flush, or belt systems are amenable to the inclusion of anaerobic digestion. In the first 

two systems, cages are suspended over a shallow pit without litter and manure is removed 

mechanically or hydraulically by flushing. In a belt system, manure is deposited on a continuous 

belt that is positioned under the cages and moves the manure to the end of the house, where 

it is placed into a manure spreader for immediate disposal or a storage structure. Because the 

manure is removed regularly, has a relatively high moisture content, and can be handled as a 

slurry, these systems are adaptable for anaerobic digester systems.

Dry systems, especially those that incorporate high-rate ventilation, promote volatilization of nitrogen into ammonia, causing a loss of nutrient value. Wet (liquid) manure management systems will 

retain the nitrogen in the manure until it is applied to the soil, assuming appropriate land application systems are used.

As of November 2010, there were five poultry anaerobic digesters in the United States. However, 

if current manure management practices are altered, the potential for biogas generation in the industry is high because of the methane generation potential of poultry manure and the large size of 

typical farms in the industry. Table 4 provides more information about U.S. poultry operations and 

identifies the states with the largest populations.
8 2

State Population (million head) Total Number of Farms (number)

Layers

Iowa 53.8 2,966

Ohio 27.1 5,255

Indiana 24.2 3,583

Pennsylvania 22.0 7,604

California 21.1 5,098

Georgia 19.3 2,870

Texas 19.1 14,562

Arkansas 14.0 3,047

North Carolina 12.7 3,736

Florida 11.8 3,361

Remaining 40 States 124.7 93,533

Total Layers 349.8 145,615

Broilers

Georgia 235.4 2,170

Arkansas 202.4 2,408

Alabama 178.3 2,263

Mississippi 150.6 1,478

North Carolina 149.9 1,879

Texas 118.6 1,872

Maryland 65.5 783

Delaware 51.1 778

Kentucky 49.8 909

Missouri 46.7 978

Remaining 40 States 354.3 17,150

Total Broilers 1,602.6 32,668

Turkeys

Minnesota 18.3 601

North Carolina 17.9 846

Arkansas 9.4 530

Missouri 8.6 868

California 6.7 469

Virginia 6.3 572

Indiana 6.0 498

South Carolina 5.5 337

Iowa 4.0 417

Wisconsin 3.7 780

Remaining 40 States 20.8 11,308

Total Turkeys 107.2 17,226

Table 4. The Top 10 States with the Largest Number of Layer, Broiler, and Turkey Populations
9
A-1 2

Appendix A

Methodology

This section describes the methodology used to estimate the maximum potential for U.S. swine 

and dairy operations to generate electricity from biogas systems. The general approach was as 

follows:

1. Characterize swine and dairy animal populations and profiles of farm sizes by state: These data 

were obtained from U.S. Department of Agriculture (USDA) published reports.

2. Estimate manure management practices: These data were obtained from EPA greenhouse gas 

inventory reports, which in turn were developed with data from the USDA, expert input, and 

observations by EPA.

3. Determine the animal populations on farms where biogas systems are feasible: The criteria described in the “Identifying Profitable Systems” section were used to identify candidate farms.

4. Estimate methane emissions and emission reductions from candidate farms: Methane emissions were estimated using EPA’s greenhouse gas inventory methodology. It was assumed that 

when farms convert to a biogas recovery system, the methane emission reduction is essentially 100 percent.

5. Estimate the methane production and electricity generation potential: These estimates were 

based on literature references and AgSTAR investigations.

6. Estimate the uncertainty associated with the analysis: An uncertainty analysis was performed 

to determine the uncertainty associated with the data presented in this report.

A more detailed discussion of these steps, including data sources and calculation methodologies, 

is presented below.

1. Characterizing State Animal Populations and Farm Profiles

The potential of individual states to reduce methane emissions from dairy and swine manures was 

based, respectively, on estimates of the number of milk cows that have calved, and the number of 

hogs and pigs in each state as reported in USDA’s 2007 Census of Agriculture.1

Census data was used to determine the number of operations in each state with 500 or more cows 

and the aggregate number of cows on these farms throughout the state. Census data was also 

used to determine the number of swine operations in each state with a confinement capacity of 

2,000 or more head, and the total number of hogs and pigs confined on these operations.

To develop the maps used in Appendix B: State Profiles, county-level population data were obtained from the USDA’s 2007 Census of Agriculture. USDA does not publicly disclose all of the 

data acquired by the census; some county-level population data were non-disclosed and therefore 

unavailable. To estimate the number of animals in the non-disclosed counties EPA first determined how many non-disclosed counties existed in each state, then subtracted the total number 

of animals in disclosed counties by the total number of animals in the state, and finally assumed 

an even distribution of these animals across non-disclosed counties. The resulting estimate of the 

number of animals in each undisclosed county was then input into the state-level maps.

1 USDA. 2009. 2007 Census of Agriculture. National Agriculture Statistics Service, Washington, DC.
A-2

2. Estimating Manure Management Practices

This analysis primarily relied upon the manure management system data discussed in EPA’s Inventory for U.S. Greenhouse Gas Emissions and Sinks: 1990-2008,2 for which the key data sources 

were USDA’s 2007 Census of Agriculture, EPA’s Office of Water, and other expert sources. More 

detailed information about the data sources and the development of the manure management 

system data for dairy and swine populations can be found in the EPA report.

3. Identifying Candidate Farms for Anaerobic Digestion

Candidate farms for feasible anaerobic digestion were assumed to be:

• Dairy farms with anaerobic lagoons or liquid slurry manure management systems and more 

than 500 cows.

• Swine farms with anaerobic lagoons or liquid slurry manure management systems and more 

than 2,000 animals, and swine farms with deep pit manure management systems and more 

than 5,000 animals. 

4. Estimating Methane Emissions by State and Animal Group

Methane emissions were estimated based on the methodologies used for EPA’s Inventory of U.S. 

Greenhouse Gas Emissions and Sinks: 1990-2008.3 These methodologies were developed by the 

International Panel on Climate Change (IPCC) and presented in the 2006 IPCC Guidelines for National Greenhouse Gas Inventories.4

Methane emission estimates were developed for each state and animal group using the following 

equation:

 Methane = Population x VS x TAM x MCF x B0 x 0.041 x 365

where

Methane = Total methane emissions from different animal types in different states and manure management systems, pounds (lb) per year

Population = Animal population

VS = Total volatile solids excretion rate, lb VS per 1,000 lb animal mass per day 

TAM = Typical animal mass, lb 

MCF = Methane conversion factor, decimal

B0 = Maximum methane producing capacity of manure, cubic feet (ft3) methane per 

lb volatile solids

0.041 = Density of methane at 25° Celsius, lb per ft3

365 = Days in a year

2 U.S. EPA. 2010. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008. Report No. EPA 430-R-10-006. Office of 

Atmospheric Programs, Washington, DC.

3 Ibid.

4 IPCC. 2006. 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Prepared by the National Greenhouse Gas 

Inventories Programme, H.S. Eggleston, L. Buendia, K. Miwa, T Ngara, and K. Tanabe (eds.). Japan.

5 USDA. 1996. Agricultural Waste Management Field Handbook. Natural Resources Conservation Service, Washington, DC.

Appendix A
A-3

Example data for two types of manure management systems are shown in Table A-1. For swine, total volatile solids (VS) was calculated using a national average VS excretion rate from the Agricultural Waste Management Field Handbook,5 which was multiplied by the typical animal mass (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.6 The maximum methane producing potential 

of manure (B0) varies by animal type and is based on values from the literature. The B0 for dairy 

cows is 3.84 ft3 of methane per pound of VS and the B0 for swine is 7.69 ft3 of methane per pound 

of VS.7,8

Methane conversion factors (MCFs) were determined for each type of manure management system and are shown in Table A-2. For dry systems, default IPCC factors were used. MCFs for liquid/

slurry storage tanks and ponds, anaerobic lagoons, and deep pit systems were calculated based on 

the forecast performance of biological systems relative to temperature changes as predicted by the 

van’t Hoff-Arrhenius equation. The MCF calculations model the average monthly ambient temperature, a minimum digester system temperature, the carryover of VS in the system from month to 

month, and a factor to account for management and design practices that result in the loss of VS 

from lagoon systems.

Example calculations: Page A-4 presents example methane emission reduction calculations 

from a biogas recovery system. Table A-1 shows the calculation of direct methane emission reductions from a biogas recovery system that replaces a manure storage tank or pond and an 

anaerobic lagoon on a farm with 500 dairy cows in California. The methane emission reduction 

from a biogas recovery system is equivalent to the methane emissions from the baseline manure 

management system that it replaces—not the amount of methane produced by the anaerobic 

digester. The amount of methane that would be collected and combusted by an anaerobic digester 

is greater than the amount of methane produced by the baseline manure management systems 

because digesters are designed to optimize methane production.

6 Pape, D. and K. Moffroid. 2008. 1990-2007 Volatile Solids and Nitrogen Excretion Rates. Dataset to EPA from ICF 

International, Washington DC.

7 Hashimoto, A.G. 1984. “Methane from Swine Manure: Effect of Temperature and Influent Substrate Composition on Kinetic 

Parameter (k).” Agricultural Wastes, 9:299-308. Elsevier B.V., Amsterdam, Kingdom of the Netherlands.

8 Morris, G.R. 1976. Anaerobic Fermentation of Animal Wastes: A Kinetic and Empirical Design Fermentation. M.S. Thesis. 

Cornell University, Ithaca, NY.
A-4

Appendix A

lb VS added

ft3CH4 3.413Btu

1000 year

The use of biogas to generate electricity also reduces CO2 emissions from conventional power 

generation sources because fewer fossil fuels are combusted by electric power plants. The following shows an example calculation for estimating reduced CO2 emissions: 

Equation Values

VS added, lb VS/yr 2,453,065

VS = Number of cows x VSE x TAM x 365 days

CH4 production, ft3 CH4/yr 10,302,875

 CH4 production = VS x 4.2ft3 CH4

Electricity generation potential, kWh/yr 877,676

 Electricity Generation potential = CH4 production x 923 Btu x kWh x 0.35 x 0.9

(0.35 is the engine efficiency and 0.9 is the on-line efficiency)

Reduction in utility carbon dioxide emissions,a ton/yr 584

 Emissions Reduction = Electricity Generation Potential x 1330 lb x 1 MWh x 1 ton

aBased on 1330 lb of carbon dioxide emitted per MWh generated, which is the national average output emission rate for 

2005 from EPA’s Emissions & Generation Resource Integrated Database (eGRID). CO2 emission rates vary across the U.S. 

depending on local electricity generation sources.

MWh 1000 kWh 2000 lbs

Table A-1. Methane Emission Reduction Impacts 

Factors

Storage Tank 

or Pond

Anaerobic 

Lagoon

Number of cows 500 500

Typical animal mass (TAM),a lb/cow 1,332 1,332

Total VS excretion rate (VSE), lb VS/1,000 lb animal mass day 10.1 10.1

B0, ft3 CH4/lb VS 3.84 3.84

MCF in California, decimal 0.346 0.741

CH4 density, lb CH4/ft3 0.041 0.041

CH4 emissions,b tons CH4/yr 67 144

CH4 emission reduction from biogas capture and utilization,c

tons CH4/yr 

67 144

Equivalent reduction in CO2 emissions,d tons CO2/yr 1,407 3,024

aThe TAM, B0, and MCF values were obtained from EPA’s Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008. 

bCH4 emissions are calculated for these examples using the equation on page A-2.

 CH4 Emissions = Number of cows x VSE x TAM x MCF x B0 x 0.041 lbs x 365 days x 1 ton

c It is assumed that biogas combustion destroys essentially 100 percent of baseline methane emissions. 

dCH4 has approximately 21 times the heat trapping capacity of CO2. 

CO2 Equivalents = CH4 Emissions x 21

ft 1000 3 year 2000 lbs
A-5

(continued on next page)

State

Dairy Swine

Tank/Pond 

Anaerobic 

Lagoon 

Tank/Pond and 

Deep Pit

Anaerobic 

Lagoon 

Alabama 0.42 0.78 0.42 0.78

Alaska 0.15 0.50 0.15 0.50

Arizona 0.62 0.80 0.39 0.76

Arkansas 0.38 0.76 0.40 0.77

California 0.35 0.74 0.32 0.73

Colorado 0.22 0.66 0.25 0.70

Connecticut 0.25 0.69 0.25 0.69

Delaware 0.32 0.74 0.33 0.74

Florida 0.54 0.79 0.53 0.79

Georgia 0.41 0.77 0.40 0.77

Hawaii 0.59 0.77 0.59 0.77

Idaho 0.25 0.69 0.24 0.68

Illinois 0.32 0.74 0.31 0.74

Indiana 0.29 0.73 0.30 0.73

Iowa 0.27 0.71 0.28 0.71

Kansas 0.33 0.75 0.33 0.75

Kentucky 0.35 0.76 0.35 0.76

Louisiana 0.47 0.79 0.48 0.79

Maine 0.20 0.62 0.20 0.62

Maryland 0.31 0.73 0.31 0.74

Massachusetts 0.24 0.67 0.25 0.68

Michigan 0.25 0.69 0.26 0.70

Minnesota 0.25 0.68 0.26 0.69

Mississippi 0.44 0.78 0.43 0.78

Missouri 0.34 0.75 0.34 0.75

Montana 0.21 0.63 0.22 0.65

Nebraska 0.29 0.72 0.29 0.72

Nevada 0.27 0.71 0.28 0.71

New Hampshire 0.21 0.64 0.22 0.65

New Jersey 0.29 0.72 0.29 0.72

New Mexico 0.30 0.73 0.29 0.72

New York 0.23 0.66 0.23 0.67

Table A-2. Methane Conversion Factors by State for 2007 (decimal)
A-6

Appendix A

State

Dairy Swine

Tank/Pond 

Anaerobic 

Lagoon 

Tank/Pond and 

Deep Pit

Anaerobic 

Lagoon 

North Carolina 0.34 0.75 0.39 0.77

North Dakota 0.23 0.66 0.23 0.66

Ohio 0.28 0.71 0.28 0.72

Oklahoma 0.39 0.77 0.36 0.76

Oregon 0.21 0.63 0.21 0.63

Pennsylvania 0.26 0.70 0.28 0.71

Rhode Island 0.26 0.70 0.26 0.70

South Carolina 0.41 0.78 0.42 0.78

South Dakota 0.26 0.70 0.27 0.70

Tennessee 0.35 0.76 0.39 0.77

Texas 0.43 0.78 0.41 0.77

Utah 0.25 0.69 0.24 0.68

Vermont 0.21 0.63 0.21 0.63

Virginia 0.30 0.73 0.33 0.74

Washington 0.21 0.63 0.22 0.65

West Virginia 0.28 0.72 0.28 0.72

Wisconsin 0.24 0.68 0.25 0.69

Wyoming 0.20 0.63 0.23 0.67

Table A-2. Methane Conversion Factors by State for 2007 (decimal) (continued)
A-7 2

5. Estimating Potential Electricity Yield from Methane Production

The estimates of the biogas production potential from dairy cow and swine manure presented in 

this report are based on the following approach:

• Methane production: Based on previously-observed values9,10,11 and expert judgment, the 

production of methane from swine manure is estimated to be 6.6 ft3 of methane per pound of 

total VS added. For dairy manure, the production of methane is assumed to be 4.2 ft3 of methane per pound of total VS added to the system.

• Heating value of methane: To calculate the energy content of methane produced in swine 

and dairy anaerobic digesters for this report, EPA used the lower heating value of methane, 923 

Btus per ft3 methane.

• Engine and on-line efficiency: Electrical output from a typical generator was estimated at 85 

kWh per 1,000 ft3 of methane. This factor is based on a thermal conversion efficiency of methane to electricity of 35 percent, and an on-line operating rate of 90 percent (to account for down 

time due to maintenance and repair).

6. Estimating Uncertainty

AgSTAR believes the largest sources of uncertainty are associated with the estimated methane 

emission calculations related to animal population data, the estimates of the number of animals 

using each type of manure management system, the VS excretion rates, the maximum methane 

production capacity data, and the methane conversion factors.

The methane emissions calculation was evaluated to determine the amount of uncertainty associated with the calculations. Using a simplified approach similar to the uncertainty analysis 

developed for EPA’s Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008, AgSTAR 

performed a Monte Carlo uncertainty analysis on the methane emission estimates calculated in 

this report. A model was developed for the uncertainty analysis and uncertainty ranges were assigned to each of the variables in the methane emission calculation. Where available, uncertainty 

ranges were obtained from the original data source (e.g., USDA publishes uncertainty data for all 

animal population data). Where not available, uncertainty ranges were estimated based on best 

professional judgment. For example, AgSTAR assigned an uncertainty range of ± 20 percent for 

the number of animals using each type of manure management system. Based on the uncertainty 

analysis, the methane emission calculations were found to have an uncertainty of approximately ± 

25 percent.

9 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.

10 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.

11 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.
A-8
B-1

Appendix B

Profiles of Top Ten Swine 

and Dairy States with Biogas 

Energy Recovery Potential
State Profile: Iowa Swine 

Swine Manure Managed in Each Waste 

Management System

Swine Farm Size

Swine Population by County

Pasture

53%

Anaerobic

Lagoon

33%

Deep Pit

4%

Solid

Storage

9%

Liquid/

Slurry

1%

54%

>5,000 head

2,000–4,999

head

30%

1–1,999

head

16%

1 Anaerobic digestion was considered feasible at all existing 

operations with flush, pit recharge, or pull-plug pit systems with at 

least 2,000 swine and at deep pit systems with at least 5,000 swine.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of swine operations 8,330

Total number of mature swine 

(000 head) 19,295

Number of feasible swine operations1 1,997

Number of mature swine at feasible 

operations (000 head) 13,824

Methane emission reduction 

potential (000 tons/year) 301

Methane production potential 

(billion ft3/year) 21.5

Electricity generation potential 

(000 MWh/yr) 1,829

< 2,000 head 2,000–5,000 head > 5,000 head

B-2
B-3 2

State Profile: North Carolina Swine 

6

Swine Manure Managed in Each Waste 

Management System

Swine Farm Size

Swine Population by County

Pasture

57%

Anaerobic

Lagoon

32%

Deep Pit

4%

Solid

Storage 7%

Liquid/

Slurry

0.2%

74%

>5,000 head

2,000–4,999

head

18%

1–1,999

head

8%

1 Anaerobic digestion was considered feasible at all existing 

operations with flush, pit recharge, or pull-plug pit systems with at 

least 2,000 swine and at deep pit systems with at least 5,000 swine.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of swine operations 2,836

Total number of mature swine 

(000 head) 10,134

Number of feasible swine operations1 939

Number of mature swine at feasible 

operations (000 head) 8,471

Methane emission reduction 

potential (000 tons/year) 203

Methane production potential 

(billion ft3/year) 13.2

Electricity generation potential 

(000 MWh/yr) 1,121

< 2,000 head 2,000–5,000 head > 5,000 head
B-4

State Profile: Minnesota Swine 

Swine Manure Managed in Each Waste 

Management System

Swine Farm Size

Swine Population by County

Pasture

18%

Anaerobic

Lagoon

50%

Deep Pit

5%

Solid Storage

26%

Liquid/

Slurry

1%

49%

>5,000 head

2,000–4,999

head

34%

1–1,999

head

17%

1 Anaerobic digestion was considered feasible at all existing 

operations with flush, pit recharge, or pull-plug pit systems with at 

least 2,000 swine and at deep pit systems with at least 5,000 swine.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of swine operations 4,382

Total number of mature swine 

(000 head) 7,652

Number of feasible swine operations1 707

Number of mature swine at feasible 

operations (000 head) 4,692

Methane emission reduction 

potential (000 tons/year) 63

Methane production potential 

(billion ft3/year) 7.3

Electricity generation potential 

(000 MWh/yr) 621

< 2,000 head 2,000–5,000 head > 5,000 head
B-5

State Profile: Illinois Swine 

Swine Manure Managed in Each Waste 

Management System

Swine Farm Size

Swine Population by County

Pasture

14%

Anaerobic

Lagoon

51%

Deep Pit

5%

Solid Storage

29%

Liquid/

Slurry

1%

55%

>5,000 head

2,000–4,999

head

27%

1–1,999

head

18%

1 Anaerobic digestion was considered feasible at all existing 

operations with flush, pit recharge, or pull-plug pit systems with at 

least 2,000 swine and at deep pit systems with at least 5,000 swine.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of swine operations 2,864

Total number of mature swine 

(000 head) 4,299

Number of feasible swine operations1 350

Number of mature swine at feasible 

operations (000 head) 2,746

Methane emission reduction 

potential (000 tons/year) 39

Methane production potential 

(billion ft3/year) 4.3

Electricity generation potential 

(000 MWh/yr) 363

< 2,000 head 2,000–5,000 head > 5,000 head
B-6

State Profile: Missouri Swine 

Swine Manure Managed in Each Waste 

Management System

Swine Farm Size

Swine Population by County

Pasture

13%

Anaerobic

Lagoon

52%

Deep Pit

5%

Solid Storage

28%

Liquid/

Slurry

2%

70%

>5,000 head

2,000–4,999

head

17%

1–1,999

head

13%

1 Anaerobic digestion was considered feasible at all existing 

operations with flush, pit recharge, or pull-plug pit systems with at 

least 2,000 swine and at deep pit systems with at least 5,000 swine.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of swine operations 2,999

Total number of mature swine 

(000 head) 3,101

Number of feasible swine operations1 154

Number of mature swine at feasible 

operations (000 head) 2,277

Methane emission reduction 

potential (000 tons/year) 34

Methane production potential 

(billion ft3/year) 3.5

Electricity generation potential 

(000 MWh/yr) 301

< 2,000 head 2,000–5,000 head > 5,000 head
B-7

State Profile: Indiana Swine 

Swine Manure Managed in Each Waste 

Management System

Swine Farm Size

Swine Population by County

Pasture

14%

Anaerobic

Lagoon

52%

Deep Pit

5%

Solid Storage

28%

Liquid/

Slurry

1%

52%

>5,000 head

2,000–4,999

head

28%

1–1,999

head

20%

1 Anaerobic digestion was considered feasible at all existing 

operations with flush, pit recharge, or pull-plug pit systems with at 

least 2,000 swine and at deep pit systems with at least 5,000 swine.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of swine operations 3,420

Total number of mature swine 

(000 head) 3,669

Number of feasible swine operations1 296

Number of mature swine at feasible 

operations (000 head) 2,238

Methane emission reduction 

potential (000 tons/year) 31

Methane production potential 

(billion ft3/year) 3.5

Electricity generation potential 

(000 MWh/yr) 296

< 2,000 head 2,000–5,000 head > 5,000 head
B-8

State Profile: Oklahoma Swine 

Swine Manure Managed in Each Waste 

Management System

Swine Farm Size

Swine Population by County

Pasture

58%

Anaerobic

Lagoon

31%

Deep Pit

4%

Solid

Storage 6%

Liquid/

Slurry

1%

94%

>5,000 head

2,000–4,999

head

3%

1–1,999

head

3%

1 Anaerobic digestion was considered feasible at all existing 

operations with flush, pit recharge, or pull-plug pit systems with at 

least 2,000 swine and at deep pit systems with at least 5,000 swine.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of swine operations 2,702

Total number of mature swine 

(000 head) 2,398

Number of feasible swine operations1 56

Number of mature swine at feasible 

operations (000 head) 2,207

Methane emission reduction 

potential (000 tons/year) 51

Methane production potential 

(billion ft3/year) 3.4

Electricity generation potential 

(000 MWh/yr) 292

< 2,000 head 2,000–5,000 head > 5,000 head
B-9

State Profile: Nebraska Swine 

Swine Manure Managed in Each Waste 

Management System

Swine Farm Size

Swine Population by County

Pasture

14%

Anaerobic

Lagoon

52%

Deep Pit

5%

Solid Storage

28%

Liquid/

Slurry

1%

58%

>5,000 head

2,000–4,999

head

19%

1–1,999

head

23%

1 Anaerobic digestion was considered feasible at all existing 

operations with flush, pit recharge, or pull-plug pit systems with at 

least 2,000 swine and at deep pit systems with at least 5,000 swine.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of swine operations 2,213

Total number of mature swine 

(000 head) 3,269

Number of feasible swine operations1 177

Number of mature swine at feasible 

operations (000 head) 2,052

Methane emission reduction 

potential (000 tons/year) 27

Methane production potential 

(billion ft3/year) 3.2

Electricity generation potential 

(000 MWh/yr) 272

< 2,000 head 2,000–5,000 head > 5,000 head
B-10

State Profile: Kansas Swine 

Swine Manure Managed in Each Waste 

Management System

Swine Farm Size

Swine Population by County

Pasture

13%

Anaerobic

Lagoon

52%

Deep Pit

5%

Solid Storage

28%

Liquid/

Slurry

2%

80%

>5,000 head

2,000–4,999

head

10%

1–1,999

head

10%

1 Anaerobic digestion was considered feasible at all existing 

operations with flush, pit recharge, or pull-plug pit systems with at 

least 2,000 swine and at deep pit systems with at least 5,000 swine.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of swine operations 1,454

Total number of mature swine 

(000 head) 1,885

Number of feasible swine operations1 80

Number of mature swine at feasible 

operations (000 head) 1,508

Methane emission reduction 

potential (000 tons/year) 22

Methane production potential 

(billion ft3/year) 2.3

Electricity generation potential 

(000 MWh/yr) 199

< 2,000 head 2,000–5,000 head > 5,000 head
B-11

State Profile: Texas Swine 

Swine Manure Managed in Each Waste 

Management System

Swine Farm Size

Swine Population by County

Pasture

57%

Anaerobic

Lagoon

30%

Deep Pit

4%

Solid

6% Storage

Liquid/

Slurry

3%

94%

>5,000 head

2,000–4,999

head

1%

1–1,999

head

5%

1 Anaerobic digestion was considered feasible at all existing 

operations with flush, pit recharge, or pull-plug pit systems with at 

least 2,000 swine and at deep pit systems with at least 5,000 swine.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of swine operations 4,471

Total number of mature swine 

(000 head) 1,156

Number of feasible swine operations1 10

Number of mature swine at feasible 

operations (000 head) 1,057

Methane emission reduction 

potential (000 tons/year) 25

Methane production potential 

(billion ft3/year) 1.6

Electricity generation potential 

(000 MWh/yr) 140

< 2,000 head 2,000–5,000 head > 5,000 head
B-12

State Profile: California Dairy

Dairy Manure Managed in Each Waste 

Management System

Dairy Farm Size

Dairy Population by County

Daily

Spread

59%

Anaerobic

Lagoon

1%

Pasture

9%

Solid

Storage

20%

Liquid/

Slurry

11%

91%

>500 head

200–499

head

8%

1–199

head

1%

1 Anaerobic digestion was considered feasible at all existing 

operations with flushed or scraped freestall barns and drylots with 

at least 500 dairy cows.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of dairy operations 2,165

Total number of mature dairy cows 

(000 head) 1,841

Number of feasible dairy cow operations1 889

Number of mature dairy cows at feasible operations (000 head) 1,352

Methane emission reduction 

potential (000 tons/year) 341

Methane production potential 

(billion ft3/year) 27.9

Electricity generation potential 

(000 MWh/yr) 2,375

< 500 head 500–1,000 head > 1,000 head
B-13 2

State Profile: Idaho Dairy

Dairy Manure Managed in Each Waste 

Management System

Dairy Farm Size

Dairy Population by County

Pasture

65%

Anaerobic

Lagoon

0.4%

Deep Pit

0.6%

Daily Spread

11%

Solid

Storage

22%

Liquid/

Slurry

0.4%

90%

>500 head

200–499

head

6%

1–199

head

4%

1 Anaerobic digestion was considered feasible at all existing 

operations with flushed or scraped freestall barns and drylots with 

at least 500 dairy cows.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of dairy operations 811

Total number of mature dairy cows 

(000 head) 536

Number of feasible dairy cow operations1 203

Number of mature dairy cows at feasible operations (000 head) 430

Methane emission reduction 

potential (000 tons/year) 99

Methane production potential 

(billion ft3/year) 8.9

Electricity generation potential 

(000 MWh/yr) 762

< 500 head 500–1,000 head > 1,000 head
B-14

State Profile: New Mexico Dairy

Dairy Manure Managed in Each Waste 

Management System

Dairy Farm Size

Dairy Population by County

Daily

Spread

62%

Anaerobic

Lagoon

9%

Solid

Storage

19%

Liquid/

Slurry

10%

99%

>500 head

200–499

head

1%

1–199

head

0%

1 Anaerobic digestion was considered feasible at all existing 

operations with flushed or scraped freestall barns and drylots with 

at least 500 dairy cows.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of dairy operations 272

Total number of mature dairy cows 

(000 head) 326

Number of feasible dairy cow operations1 110

Number of mature dairy cows at feasible operations (000 head) 261

Methane emission reduction 

potential (000 tons/year) 64

Methane production potential 

(billion ft3/year) 5.3

Electricity generation potential 

(000 MWh/yr) 455

< 500 head 500–1,000 head > 1,000 head
B-15 2

State Profile: Texas Dairy

Dairy Manure Managed in Each Waste 

Management System

Dairy Farm Size

Dairy Population by County

58%

Anaerobic

Lagoon

1%

Deep Pit

8%

Daily Spread

11%

Solid

Storage

22%

Liquid/

Slurry

82%

>500 head

200–499

head

11%

1–199

head

7%

1 Anaerobic digestion was considered feasible at all existing 

operations with flushed or scraped freestall barns and drylots with 

at least 500 dairy cows.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of dairy operations 1,293

Total number of mature dairy cows 

(000 head) 404

Number of feasible dairy cow operations1 155

Number of mature dairy cows at feasible operations (000 head) 266

Methane emission reduction 

potential (000 tons/year) 66

Methane production potential 

(billion ft3/year) 5.0

Electricity generation potential 

(000 MWh/yr) 429

< 500 head 500–1,000 head > 1,000 head
B-16

State Profile: Wisconsin Dairy

Dairy Manure Managed in Each Waste 

Management System

Dairy Farm Size

Dairy Population by County

Pasture

16%

Anaerobic

Lagoon

3%

Deep Pit

12%

Daily Spread

35%

Solid

Storage

27%

Liquid/

Slurry

7%

21%

>500 head

200–499

head

19%

1–199

head

60%

1 Anaerobic digestion was considered feasible at all existing 

operations with flushed or scraped freestall barns and drylots with 

at least 500 dairy cows.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of dairy operations 14,158

Total number of mature dairy cows 

(000 head) 1,249

Number of feasible dairy cow operations1 251

Number of mature dairy cows at feasible operations (000 head) 238

Methane emission reduction 

potential (000 tons/year) 41

Methane production potential 

(billion ft3/year) 4.5

Electricity generation potential 

(000 MWh/yr) 386

< 500 head 500–1,000 head > 1,000 head
B-17 2

State Profile: Washington Dairy

Dairy Manure Managed in Each Waste 

Management System

Dairy Farm Size

Dairy Population by County

Pasture

51%

Anaerobic

Lagoon

1%

Deep Pit

10%

Solid

Storage

21%

Liquid/

Slurry

17%

75%

>500 head

200–499

head

16%

1–199

head

9%

1 Anaerobic digestion was considered feasible at all existing 

operations with flushed or scraped freestall barns and drylots with 

at least 500 dairy cows.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of dairy operations 817

Total number of mature dairy cows 

(000 head) 243

Number of feasible dairy cow operations1 125

Number of mature dairy cows at feasible operations (000 head) 163

Methane emission reduction 

potential (000 tons/year) 35

Methane production potential 

(billion ft3/year) 3.4

Electricity generation potential 

(000 MWh/yr) 294

< 500 head 500–1,000 head > 1,000 head
B-18

State Profile: Arizona Dairy

Dairy Manure Managed in Each Waste 

Management System

Dairy Farm Size

Dairy Population by County

Daily

Spread

62%

Anaerobic

Lagoon

9%

Solid

Storage

19%

Liquid/

Slurry

10%

98%

>500 head

200–499

head

1%

1–199

head

1%

1 Anaerobic digestion was considered feasible at all existing 

operations with flushed or scraped freestall barns and drylots with 

at least 500 dairy cows.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of dairy operations 182

Total number of mature dairy cows 

(000 head) 184

Number of feasible dairy cow operations1 54

Number of mature dairy cows at feasible operations (000 head) 146

Methane emission reduction 

potential (000 tons/year) 44

Methane production potential 

(billion ft3/year) 3.1

Electricity generation potential 

(000 MWh/yr) 263

< 500 head 500–1,000 head > 1,000 head
B-19 2

State Profile: Michigan Dairy

Dairy Manure Managed in Each Waste 

Management System

Dairy Farm Size

Dairy Population by County

Pasture

28%

Anaerobic

Lagoon

3%

Deep Pit

6%

Daily Spread

23%

Solid

Storage

37%

Liquid/

Slurry

3%

43%

>500 head

200–499

head

22%

1–199

head

35%

1 Anaerobic digestion was considered feasible at all existing 

operations with flushed or scraped freestall barns and drylots with 

at least 500 dairy cows.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of dairy operations 2,647

Total number of mature dairy cows 

(000 head) 344

Number of feasible dairy cow operations1 107

Number of mature dairy cows at feasible operations (000 head) 138

Methane emission reduction 

potential (000 tons/year) 26

Methane production potential 

(billion ft3/year) 2.9

Electricity generation potential 

(000 MWh/yr) 246

< 500 head 500–1,000 head > 1,000 head
B-20

State Profile: New York Dairy

Dairy Manure Managed in Each Waste 

Management System

Dairy Farm Size

Dairy Population by County

Pasture

12%

Anaerobic

Lagoon

2%

Deep Pit

45%

Daily Spread

17%

Solid

Storage

17%

Liquid/

Slurry

7%

91%

>500 head

200–499

head

8%

1–199

head

1%

1 Anaerobic digestion was considered feasible at all existing 

operations with flushed or scraped freestall barns and drylots with 

at least 500 dairy cows.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of dairy operations 5,683

Total number of mature dairy cows 

(000 head) 626

Number of feasible dairy cow operations1 111

Number of mature dairy cows at feasible operations (000 head) 109

Methane emission reduction 

potential (000 tons/year) 18

Methane production potential 

(billion ft3/year) 2.1

Electricity generation potential 

(000 MWh/yr) 177

< 500 head 500–1,000 head > 1,000 head
B-21 2

State Profile: Colorado Dairy

Dairy Manure Managed in Each Waste 

Management System

Dairy Farm Size

Dairy Population by County

Pasture

64%

Anaerobic

Lagoon

0.5%

Deep Pit

1%

Daily Spread

11%

Solid

Storage

23%

Liquid/

Slurry

0.7%

85%

>500 head

200–499

head

10%

1–199

head

5%

1 Anaerobic digestion was considered feasible at all existing 

operations with flushed or scraped freestall barns and drylots with 

at least 500 dairy cows.

Market Opportunities to Generate

Electricity with Anaerobic Digestion (2007)

Total number of dairy operations 449

Total number of mature dairy cows 

(000 head) 127

Number of feasible dairy cow operations1 54

Number of mature dairy cows at feasible operations (000 head) 97

Methane emission reduction 

potential (000 tons/year) 22

Methane production potential 

(billion ft3/year) 2.0

Electricity generation potential 

(000 MWh/yr) 174

< 500 head 500–1,000 head > 1,000 head
AgSTAR is an outreach program jointly sponsored by the U.S. 

Environmental Protection Agency, the U.S. Department of 

Agriculture, and the U.S. Department of Energy. The program 

encourages the use of biogas recovery technologies at confined 

animal feeding operations that manage manure as liquids or 

slurries. These technologies reduce emissions of methane (a 

potent greenhouse gas), generate clean energy, and achieve other 

environmental benefits. For additional information, please visit 

our website at www.epa.gov/agstar.