Methane Capture: Options for Greenhouse Gas Emission Reduction

Congressional research reportJan 7, 2011

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Methane Capture: Options for Greenhouse

Gas Emission Reduction

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R40813

CRS Report for Congress

Prepared for Members and Committees of Congress

Methane Capture: Options for Greenhouse Gas Emission Reduction

Summary

Research on climate change has identified a wide array of sources that emit greenhouse gases

(GHGs). Among the six gases that have generally been the primary focus of concern, methane is

the second-most abundant, accounting for approximately 8% of total U.S. GHG emissions in

2008. Methane is emitted from a number of sources. The most significant are agriculture (both

animal digestive systems and manure management); landfills; oil and gas production, refining,

and distribution; and coal mining.

As policymakers consider options to reduce GHG emissions, methane capture projects offer an

array of possible reduction opportunities, many of which utilize proven technologies. Methane

capture projects (e.g., landfill gas projects, anaerobic digestion systems) restrict the release of

methane into the atmosphere. The methane captured can be used for energy or flared. Methane

capture challenges differ depending on the source. Most methane capture technologies face

obstacles to implementation, including marginal economics in many cases, restricted pipeline

access, and various legal issues.

Some of the leading methane capture options under discussion include market-based emission

control programs, carbon offsets, emission performance standards, and maintaining existing

programs and incentives. At present, methane capture technologies are supported by tax

incentives in some cases, by research and demonstration programs in others, by regulation in the

case of the largest landfills, and by voluntary programs. Congress could decide to address

methane capture in a number of different ways, including (1) determining the role of methane

capture in energy and environmental legislation; (2) determining whether methane capture should

be addressed on an industry-by-industry basis; and (3) determining if current methane capture

initiatives will be further advanced with legislative action regardless of other facets of the

environmental policy debate. What role methane capture would play in prospective regulations to

control GHGs is among the issues that Congress faces.

A few government programs have supported the capture of methane to mitigate climate change.

The Methane-to-Markets Partnership, administered by the Environmental Protection Agency

(EPA), is an international initiative to reduce global methane emissions. EPA also oversees a

variety of voluntary programs related to the Methane-to-Markets initiative (e.g., Coalbed

Methane Outreach Program, Natural Gas STAR Program, Landfill Methane Outreach Program,

AgSTAR Program).

This report discusses alternatives for addressing methane capture, sources of methane,

opportunities and challenges for methane capture, and current federal programs that support

methane recovery.

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Methane Capture: Options for Greenhouse Gas Emission Reduction

Contents

Introduction ................................................................................................................................1

Policy Options for Addressing Methane Capture .........................................................................1

Market-Based Emission Control Programs ............................................................................1

Carbon Offsets ......................................................................................................................3

Emission Performance Standards ..........................................................................................4

Maintain Existing Programs/Incentives .................................................................................5

Legislative Proposals Concerning Methane Capture ....................................................................5

Methane: A Primer ......................................................................................................................5

Global Warming Potential .....................................................................................................6

Sources of Methane...............................................................................................................6

Domestic ........................................................................................................................6

International....................................................................................................................7

Methane Use and Storage......................................................................................................8

Opportunities and Challenges for Methane Capture.....................................................................9

Agriculture.......................................................................................................................... 10

Landfill Gas........................................................................................................................ 10

Oil and Natural Gas ............................................................................................................ 11

Coalbed Methane ................................................................................................................ 12

Concerns Applicable to All Sources..................................................................................... 13

Federal Support for Methane Capture........................................................................................ 13

Methane-to-Markets Partnership ......................................................................................... 13

Voluntary Methane Programs .............................................................................................. 14

Federal Energy Management Program................................................................................. 14

Tax Incentives..................................................................................................................... 14

DOE Methane Hydrate Research and Development............................................................. 16

Figures

Figure 1. 2008 U.S. Sources of Anthropogenic Methane Emissions .............................................7

Figure 2. U.S. Underground Natural Gas Storage Facilities, Close of 2007 ..................................9

Tables

Table 1. Selected Sources of U.S. Methane Emissions and Potential Number of Entities

Subject to Emission Control Program.......................................................................................2

Table 2. Top Five Methane-Emitting Countries in 2005 ...............................................................8

Table 3. U.S. Methane Emissions by Source................................................................................9

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Methane Capture: Options for Greenhouse Gas Emission Reduction

Appendixes

Appendix. World Methane Emissions by Sector in 2005............................................................ 17

Contacts

Author Contact Information ...................................................................................................... 18

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Methane Capture: Options for Greenhouse Gas Emission Reduction

Introduction

In the climate change policy debate, methane capture projects have garnered attention for their

ability to mitigate greenhouse gas emissions. Methane capture projects prevent the release of

methane, a potent greenhouse gas (GHG), into the atmosphere. The captured methane is generally

flared or used for energy purposes.1 The U.S. Environmental Protection Agency (EPA) has

identified four sources of methane with the greatest potential for capture in the near term:

landfills, coal mines, agriculture, and oil and gas systems. The amount of methane captured from

each will depend on legislative developments, regulations, economics, technology, and outreach.

Methane (CH4) constituted approximately 8% of U.S. GHG emissions in 2008.2 Anthropogenic

(human-related) sources of methane in the United States include enteric fermentation,3 landfills,

natural gas systems, coal mines, and manure management. Efforts to reduce emissions of

methane—the second-most important GHG after carbon dioxide (CO2)—could play a significant

role in climate change mitigation.

This report will discuss the policy options for addressing methane capture (and their

implications), legislative proposals for methane capture, domestic and international sources of

methane, opportunities and challenges for methane capture, and federal programs that support

methane capture.

Policy Options for Addressing Methane Capture

If policymakers decide to address methane emissions, multiple strategies are available that would

either encourage or require methane capture: market-based legislative approaches, such as a capand-trade program or emissions fees; carbon offsets or credits as a complementary design element

of a market-based approach; emission performance standards; and/or maintaining existing

programs and incentives.4 Policymakers may consider using different strategies for different

methane emission sources. These strategies and related issues are discussed below.

Market-Based Emission Control Programs

One option for policymakers is to include methane emission sources as covered entities in a

market-based greenhouse gas (GHG) emission control program. Market-based mechanisms that

limit GHG emissions can be divided into two types: those that focus on quantity control (e.g., a

cap-and-trade program) and those that focus on price control (e.g., emissions fees, often called a

Flaring is the combustion of the gas without commercial purposes. Flaring produces carbon dioxide, which is a less

potent greenhouse gas than methane.

U.S. Environmental Protection Agency, 2010 U.S. Greenhouse Gas Inventory Report, EPA 430-R-10-006, April

2010, http://www.epa.gov/climatechange/emissions/usinventoryreport.html.

Enteric fermentation is the production and release of methane via eructation (burping) and flatulence as ruminant

animals digest their feed.

The climate-changing impact of multiple greenhouse gases is commonly measured and compared using their global

warming potential as expressed in units of carbon dioxide equivalent. Therefore, many concepts and actions are

preceded with the word carbon which may actually account for an assortment of greenhouse gases in both quantity and

quality (e.g., carbon tax, carbon offset).

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carbon tax). Although each approach has its own set of advantages and disadvantages,5 both

would place a price on methane emissions from covered sources. To the extent that they are able,

covered entities (those subject to the cap or fee) would likely pass the emissions price through to

consumers. For example, if solid waste landfills were subject to a cap or fee based on methane

emissions, the landfill operators would likely raise the price of waste disposal to account for the

new cost of emissions. Economic theory suggests that a higher waste disposal price would

provide a market incentive for consumers to generate less waste, thus decreasing landfill methane

emissions.

Cap-and-trade and carbon tax proposals6 in the 111th Congress generally did not apply to methane

emissions from the primary sources of such emissions. The main rationale for excluding some of

these groups involved the administrative costs of covering them under an emissions program. As

Table 1 indicates, the number of methane emission sources is relatively large compared to their

total contribution to U.S. GHG emissions. This is particularly the case for methane emissions

from the agriculture sector.

Table 1. Selected Sources of U.S. Methane Emissions and Potential Number of

Entities Subject to Emission Control Program

Methane Emission Source

Percentage of U.S.

GHG Emissions

(2008 data)

CH4 from livestock (enteric fermentation)

Potential Applications

Entity

Number

2.0

Cattle operationsa

CH4 from landfills

1.8

Landfillsb

967,440

CH4 from natural gas systems

1.4

Natural gas processors

CH4 from coal mines

0.9

Active coal minesc

1,374

CH4 from manure management

0.6

Cattle operations;

Swine operationsd

967,440

65,640

1,831

530

Source: CRS analysis of data from USDA and EPA.

U.S. Department of Agriculture, Farms, Land in Farms, and Livestock Operations: 2007 Summary (2008).

U.S. Environmental Protection Agency, 2010 U.S. Greenhouse Gas Inventory Report, EPA 430-R-10-006, April

2010, http://www.epa.gov/climatechange/emissions/usinventoryreport.html, citing 16th Annual BioCycle

Nationwide Survey: The State of Garbage in America (2008).

Methane from underground mines, which accounts for about 61% of coal mine methane, is removed

through ventilation systems for safety reasons. These emissions would be easier to monitor under an

emission control program than aboveground coal mine methane emissions. Number of active coal mines

from Energy Information Administration (EIA), “Coal Production and Number of Mines by State and Mine

Type,” at http://www.eia.gov.

U.S. Department of Agriculture, Farms, Land in Farms, and Livestock Operations: 2007 Summary (2008). Other

animals—chickens, horses, and sheep—contribute approximately 10% of the total emissions from manure

(EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2006 (April 2008), table 6-6).

See CRS Report R40242, Carbon Tax and Greenhouse Gas Control: Options and Considerations for Congress, by

(name redacted) and (name redacted).

See CRS Report R40556, Market-Based Greenhouse Gas Control: Selected Proposals in the 111th Congress, by

(name redacted), (name redacted), and (name redacted).

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Although an even larger number of sources (e.g., industries, automobiles, buildings) generate CO2

emissions, the vast majority of CO2 emissions can be addressed by subjecting a relatively small

number of entities to an emissions cap. This opportunity exists for CO2 emissions, because

policymakers could apply the emissions cap upstream of the actual emissions, typically where the

emission inputs are produced or enter the U.S. economy.7 Under this approach, policymakers

could address CO2 emissions from fossil fuel combustion and non-energy uses—in aggregate

82% of U.S. GHG emissions—by covering fewer than 2,500 entities.8 For most methane sources,

particularly in the agriculture sector, an analogous opportunity does not exist.

In addition, some of the source categories identified in Table 1 may be more amenable to

emissions coverage than others. For example, roughly 25% of the methane emissions from

natural gas systems comes from field production,9 which may be impractical to monitor and

measure accurately. 10 The remaining 75% primarily involves accidental releases sometimes

referred to as fugitive emissions.11 Landfill methane may offer fewer challenges in terms of

measurement, but the largest landfills are already reducing methane emissions pursuant to landfill

gas reduction requirements established by the Clean Air Act (42 U.S.C. 7401 et seq.).12

Carbon Offsets

Within the framework of a cap-and-trade or carbon tax system, policymakers could encourage

methane mitigation activities by allowing methane capture as an eligible offset project or as an

emission (or tax) credit. A carbon offset is a measurable reduction, avoidance, or sequestration of

GHG emissions from an emission source not covered by a cap-and-trade system. Most of the capand-trade proposals offered in the 111th Congress allowed offsets (under varying conditions) as a

compliance alternative.13

Offsets would likely make an emissions program more cost-effective by (1) providing an

incentive for non-regulated sources to generate emission reductions and (2) expanding emission

compliance opportunities for regulated entities. The main concern with offset projects is whether

or not they represent real emission reductions. For offsets to be real, a ton of CO2-equivalent

An upstream approach would apply the cap to fossil fuels when they enter the U.S. economy, either at the mine,

wellhead, or another practical “chokepoint” in the production chain. Imported fuels would be addressed at their point of

entry into the United States.

For more on these issues, see CRS Report R40242, Carbon Tax and Greenhouse Gas Control: Options and

Considerations for Congress, by (name redacted) and (name redacted).

As described by EPA, “wells are used to withdraw raw gas from underground formations. Emissions arise from the

wells themselves, gathering pipelines, and well-site gas treatment facilities such as dehydrators and separators. Fugitive

emissions and emissions from pneumatic devices account for the majority of CH4 emissions. Flaring emissions account

for the majority of the non-combustion CO2 emissions.” EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks:

1990-2006 (April 2008).

See, for example, Gilbert Metcalf and David Weisbach, The Design of a Carbon Tax (June 2008), Tufts University

and the University of Chicago.

U.S. Environmental Protection Agency, 2010 U.S. Greenhouse Gas Inventory Report, EPA 430-R-10-006, April

2010, http://www.epa.gov/climatechange/emissions/usinventoryreport.html.

Landfill gas New Source Performance Standards (NSPS) went into effect in 1996. See U.S. Environmental

Protection Agency, “Standards of Performance for New Stationary Sources and Guidelines for Control of Existing

Sources: Municipal Solid Waste Landfills,” 61 Federal Register 9914, March 12, 1996.

For more information pertaining to carbon offsets, see CRS Report RL34436, The Role of Offsets in a Greenhouse

Gas Emissions Cap-and-Trade Program: Potential Benefits and Concerns, by (name redacted).

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emissions reduced from an offset project should equate to a ton emitted from a capped source,

such as a smokestack or exhaust pipe, and would not have occurred without the regulatory

incentive. This objective presents challenges because some offset projects are difficult to

measure.

However, some methane capture projects, such as those from landfills or coal mines, are

generally considered to be of higher quality (more credible) than other offset types. These

projects are relatively easy to measure and verify, and in many cases would likely not occur if not

for the financing provided by an offset market. Therefore, the challenge of proving

“additionality” is easier to overcome. 14

The advantage some methane capture projects have over other GHG mitigation activities may

spur policymakers to control these methane releases directly (via some of the options discussed),

instead of encouraging abatement through an offset market. Moreover, allowing certain activities

as offsets, while imposing emission controls or caps on others, may raise issues of fairness. For

example, why should specific GHG emission sources, such as electricity generators, be capped

while other sources, such as landfill or animal feedlot methane, have the potential to generate

financial gain for owners and/or operators through the offset market?

Emission Performance Standards

Another option for policymakers is to require emission performance standards for particular

methane emission sources. This approach has historically represented the core of U.S. federal air

pollution policy. New legislation would not be required to pursue the standards approach. The

ability to limit methane emissions already exists under various Clean Air Act authorities that

Congress has enacted, a point underlined by the Supreme Court in an April 2007 decision,

Massachusetts v. EPA. Although the current EPA Administrator has stated a preference for

controlling GHG emissions through new legislation, the agency has begun to take actions that

could lead to GHG emission performance standards from particular sources.15

Pursuant to Clean Air Act authority, EPA would achieve emission reductions by setting emission

performance standards on each source of pollution, or requiring that sources use a particular type

of technology, such as the “best available control technology.” Although emission performance

standards have proven to be effective through decades of experience, source-by-source regulation

often cannot achieve, by itself, a desired emission reduction target at the least collective cost.

Moreover, performance standards can be difficult to adjust as circumstances (e.g., technologies)

change. On the other hand, they may be less expensive where measurement, administrative, or

transaction costs are high relative to emission control costs. This approach may be a practical

option for certain specific sources of methane emissions.

Additionality refers to whether the offset project represents an activity that is beyond what would have occurred

under a business-as-usual scenario. In other words, would the emission reductions or sequestration have happened

anyway? Additionality is generally considered to be the most significant factor that determines the integrity of the

offset.

For more information on these developments, see CRS Report R40585, Climate Change: Potential Regulation of

Stationary Greenhouse Gas Sources Under the Clean Air Act, by (name redacted) and (name redacted); Environmental

Protection Agency, “EPA Finds Greenhouse Gases Pose Threat to Public Health, Welfare / Proposed Finding Comes in

Response to 2007 Supreme Court Ruling ,” press release, April 17, 2009, http://yosemite.epa.gov/opa/admpress.nsf/0/

0EF7DF675805295D8525759B00566924.

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Maintain Existing Programs/Incentives

As discussed later in this report, the federal government currently supports several programs that

stimulate methane capture. In addition to these initiatives, which are generally voluntary in

nature, since 1996 the Clean Air Act has imposed air emission standards on large solid waste

landfills. However, as discussed below, the vast majority of landfills are not covered under the

1996 standards, and there is room to increase the amount of methane captured from solid waste

landfills. Moreover, the primary objective of these standards is to reduce the hazardous air

pollutants and non-methane organic compounds contained in landfill gas, not to reduce methane

emissions for climate-related reasons. Regardless, as mentioned above, the existing Clean Air Act

authorities could be used to address a wider universe of methane sources, for the express purpose

of controlling GHG emissions, or, as in the case of landfills, for multiple purposes.

Because methane can be used as an energy source, the existing marketplace provides some

incentive to capture methane for this purpose. If a GHG emission control program were

implemented, such a program would increase this incentive by raising the price of traditional

high-carbon energy sources (e.g., coal) relative to captured methane. The strength of the incentive

would depend on the stringency of the emission control program.

Legislative Proposals Concerning Methane Capture

The 111th Congress introduced numerous bills related to methane emissions. One group of bills

specified methane as a GHG, promoted biogas production, supported landfill gas recovery

projects, and addressed or promoted methane capture.16 Another set of bills not related to methane

capture prohibited permit issuance under the Clean Air Act for methane emissions from biological

processes associated with livestock operations, among other provisions, and expanded methane

hydrate research.17

H.R. 2454, which passed the House on June 26, 2009,18 contained numerous energy provisions,

including a GHG emission cap-and-trade system. If enacted, the cap-and-trade program would

have allowed some methane capture activities to generate offsets. However, some methane

sources might have been subject to emission performance standards. One enacted piece of

legislation (P.L. 111-5, the American Recovery and Reinvestment Act of 2009) extended and

expanded existing incentives for open-loop biomass and landfill gas electricity production and

created a new incentive for the same activities.

Methane: A Primer

Methane—a colorless, odorless gas with the molecular formula CH4—is produced by

“methanogenic” bacteria that decompose organic matter in the absence of oxygen. Sometimes

referred to as “marsh gas,” methane is flammable, can cause suffocation, and can be explosive in

Biogas consists of 60%-70% methane, 30%-40% carbon dioxide, and trace amounts of other gases.

Methane hydrates—a mixture of water and natural gas—are a potentially huge global energy resource.

See CRS Report R40643, Greenhouse Gas Legislation: Summary and Analysis of H.R. 2454 as Passed by the House

of Representatives , coordinated by (name redacted) and (name redacted).

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low concentrations in air. It is the primary component (70%-90%) of natural gas fuel. Roughly

27% of total U.S. energy consumed in 2009 was natural gas.19 Consumption is spread across a

wide array of economic sectors, with electric power generation and industrial consumption

accounting for roughly 62% of total volume delivered to consumers; residential use, 23%; and

commercial use, 15%, in 2009.20

Global Warming Potential

Global warming potential (GWP) is an estimate of how much a GHG affects climate change over

a quantity of time relative to CO2, which has a GWP value of 1. Methane is a potent GHG with a

global warming potential of 21.21 Over a 100-year timeframe, methane is 21 times more effective

than CO2 at trapping heat in the atmosphere. In other words, it takes 21 tons of CO2 to equal the

effect of 1 ton of CH4. Methane has a relatively short atmospheric lifetime (approximately 12

years) when compared to the atmospheric lifetime of carbon dioxide; thus efforts to capture

methane from anthropogenic sources provide more near-term climate change abatement than

capturing or reducing comparable amounts of CO2, but less multi-decadal abatement.

Once methane or other GHGs are converted, using GWP or other methods, they can be expressed

in a common unit of measurement: carbon dioxide-equivalent (CO2-eq. or CO2e). CO2e both

takes into account the potency of each gas and expresses the quantity of the gas. Carbon dioxideequivalent has been adopted as a principal unit of measurement to aggregate or make

comparisons across GHGs. CO2e expresses the tons of a greenhouse gas in the equivalent

effect of tons of CO2 on climate change (more specifically, on “radiative forcing”).22 Once all

gases are converted to CO2e, they can be compared or added together.

Sources of Methane

Domestic

The top three anthropogenic sources of the roughly 567 million metric tons CO2e of methane

emitted in 2008 were enteric fermentation, landfills, and natural gas systems.23 These three

sources combined were responsible for about 64% of total U.S. methane emissions (see Figure

1). There are also natural sources of methane emissions, such as wetlands and releases of natural

BP, BP Statistical Review of World Energy, June 2010.

For more information on market conditions for natural gas, see CRS Report R40487, Natural Gas Markets: An

Overview of 2008, by (name redacted); and the Energy Information Administration,

Natural Gas Consumption by End

Use, December 2010 http://www.eia.doe.gov/dnav/ng/ng_cons_sum_dcu_nus_a.htm ,

The Intergovernmental Panel on Climate Change (IPCC) assigns methane a carbon dioxide equivalent, or global

warming potential, of 21. Intergovernmental Panel on Climate Change, Climate Change 2007: The Physical Science

Basis (2007), p. 212.

“Radiative forcing” is defined as the change in the difference between incoming and outgoing radiation at the top of

the troposphere. CO2e is not exactly equivalent to radiative forcing, but it is similar and easier to understand for policy

purposes than the main alternative, watts per square meter (W/m2).

1 teragram = 1 million metric tons. A Tg CO2e (teragram of carbon dioxide equivalent) is a principal unit of

measurement across greenhouse gases. See footnote 3 for the definition of enteric fermentation. U.S. Environmental

Protection Agency, 2010 U.S. Greenhouse Gas Inventory Report, EPA 430-R-10-006, April 2010, http://www.epa.gov/

climatechange/emissions/usinventoryreport.html.

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gas from geologic formations. Natural sources of methane are generally assumed to account for

30% of an annual methane emissions inventory that includes natural and anthropogenic sources. 24

Figure 1. 2008 U.S. Sources of Anthropogenic Methane Emissions

Source: U.S. Environmental Protection Agency, 2010 U.S. Greenhouse Gas Inventory Report, EPA 430-R-10-006,

April 2010, http://www.epa.gov/climatechange/emissions/usinventoryreport.html.

Note: The “forest land remaining forest land” category contains forest land that stays forest land based on IPCC

guidance for defining inventory categories. Methane emissions from the category “forest land remaining forest

land” are attributed to wildfires and prescribed fires on managed forest land.

International

Methane accounted for nearly 17% of global greenhouse gas emissions in 2005.25 Asia is reported

as having emitted the most methane on a regional basis. China, India, the United States, the

European Union, and Brazil are the top five methane-emitting countries (see Table 2). The

agriculture sector is the leading source of methane emissions for the world (see Appendix). 26

Kathleen Hogan, Current and Future Methane Emissions from Natural Sources, United States Environmental

Protection Agency, EPA 430-R-93-011, Washington , DC, August 1993.

World Resources Institute, Climate Analysis Indicators Tool (CAIT) Version 6.0., Washington, DC, 2009. Data

quality for the global methane emission estimates reported varies due to uncertainty and possible inconsistency

depending on reporting agencies adherence to data collection and interpretation for standardized definitions and

measurements for each sector and territory.

The World Resources Institute includes methane emissions from the following activities for the agriculture sector:

(continued...)

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One analysis of global average atmospheric concentrations for methane indicates that, while

growth leveled off for approximately a 15-year period beginning in the early 1990s, methane

concentrations may have begun to increase again in 2007, possibly due to warmer temperatures in

the Arctic and increased precipitation in the tropics. 27 Global methane emissions from natural

sources are estimated at approximately 208 million metric tons of methane per year.28

Table 2.Top Five Methane-Emitting Countries in 2005

Country

Million MT (Tg) CO2e

% of World Total

China

853

India

548

United States

521

European Union

449

Brazil

389

Source: Climate Analysis Indicators Tool (CAIT) Version 6.0 (Washington, DC: World Resources Institute,

2009).

Notes: Excludes land use change.

Methane Use and Storage

Methane may be captured in its pure form or as a component of biogas, depending on the

source.29 The methane captured can be “flared” (combusted without commercial purpose) or used

to generate heat or electricity. Flaring the gas destroys the methane and yields carbon dioxide

(CO2) and water.30 The release of carbon dioxide as a result of flaring is less risky in terms of

climate forcing than releasing the methane or biogas as is into the atmosphere.

Captured methane is stored chiefly underground as a constituent of natural gas. Underground

storage options include depleted gas or oil fields, aquifers, or salt cavern formations (see Figure

2). A less common option is the storage of natural gas in liquid form. Liquefied natural gas (LNG)

is roughly one six-hundredth the volume of gaseous natural gas, allowing for transport by ship to

areas that are inaccessible via a natural gas pipeline. 31

(...continued)

enteric fermentation from livestock, livestock manure management, rice cultivation, and other agricultural sources. The

sole exception, according to CAIT data compiled for 2005, is the United States, where the greatest sources of

methane—the fugitive emission sector and the waste sector (e.g., landfills, wastewater treatment)—surpass the

agriculture sector slightly. However, 2007 data from EPA shown in Figure 1 depicts the agriculture sector as the

largest U.S. methane emission source. The World Resources Institute includes methane emissions from the following

activities for the fugitive emission sector: oil and natural gas systems, and coal mining.

For more information, see CRS Report RL34266, Climate Change: Science Highlights, by (name redacted), and E.J.

Dlugokencky, L. Bruhwiler, and J.W.C. White, et al., “Observational Constraints on Recent Increases in the

Atmospheric CH4 Burden,” Geophysical Research Letters, August 18, 2009.

Environmental Protection Agency, Methane and Nitrous Oxide Emissions from Natural Sources, EPA-430-R-10001, Washington, DC, April 2010, http://epa.gov/methane/pdfs/Methane-and-Nitrous-Oxide-Emissions-From-NaturalSources.pdf.

Biogas consists of 60%-70% methane, 30%-40% carbon dioxide, and trace amounts of other gases.

Stoichiometric equation for biogas combustion: CH4 + 2O2 → CO2 + 2H2O.

Energy Information Administration, Department of Energy, The Global Liquefied Natural Gas Market: Status &

(continued...)

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Figure 2. U.S. Underground Natural Gas Storage Facilities, Close of 2007

Source: Energy Information Administration, Office of Oil & Gas, Natural Gas Division, Gas Transportation

Information System, December 2008.

Notes: There are no natural gas storage facilities in Alaska or Hawaii.

Opportunities and Challenges for Methane Capture

Capturing methane from various sectors of the U.S. economy requires different strategies because

some strategies may be more economically feasible for specific emission sources or locations.

Policy laid out in forthcoming energy and environmental proposals may further provide technical

and economic incentives to overcome barriers—past and present—to methane capture. The

following section summarizes opportunities and challenges for methane capture from the top four

sources of methane: agriculture, landfills, oil and natural gas systems, and coalbed methane (see

Table 3).

Table 3. U.S. Methane Emissions by Source

(million metric tons CO2e)

Source

2000

2006

2007

2008

Agriculture—Enteric Fermentation

136.8

139.0

141.2

140.8

Landfills

120.7

127.1

126.5

126.3

Natural Gas Systems

130.7

103.1

99.5

96.4

(...continued)

Outlook, DOE/EIA-0637, December 2003.

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Source

2000

2006

2007

2008

Coal Mining

60.4

58.3

58.1

67.6

Agriculture—Manure Management

38.6

42.3

45.9

45.0

Source: U.S. Environmental Protection Agency, 2010 U.S. Greenhouse Gas Inventory Report, EPA 430-R-10-006,

April 2010, http://www.epa.gov/climatechange/emissions/usinventoryreport.html.

Agriculture

Methane emissions from the U.S. agriculture sector are mostly attributable to enteric fermentation

and manure management, the largest and fifth-largest sources of methane emissions in 2008,

respectively. 32 Ruminant animals (e.g., cattle, sheep) are the major emitters of methane via enteric

fermentation, a non-point source of methane emissions. The amount of methane emitted from

enteric fermentation depends on the feed quality and amount of feed ingested by the animal.

Options to reduce methane emissions from enteric fermentation include improved animal

productivity and feed management.33

Some manure management systems (e.g., storage of liquid or slurry manure in a waste storage

structure) are a point-source of methane emissions. Methane released from the anaerobic

decomposition of manure depends mainly on the storage temperature, storage time, and manure

composition. Methane emissions from some manure management systems may be captured with

an anaerobic digestion system (AD system) that flares the gas or uses it for energy purposes. 34

Barriers to methane capture from manure management include limited technology and

information exchange between agricultural producers and the technology transfer community,

high up-front capital costs for AD systems, unsatisfactory technology reliability, and low rates

paid by some utilities for the electricity generated.

Landfill Gas

Landfills were the second-largest U.S. source of methane emissions in 2008.35 Landfill gas—a

mixture of roughly 50% methane and 50% carbon dioxide, but including small amounts of other

gases—is released into the atmosphere if not captured. The amount of gas produced at any given

landfill depends on the amount of organic material in the waste, the landfill’s design, the climate

at the site of the landfill, and the operating practices used by the site’s operator. In general, large

amounts of organic waste and high levels of moisture in a landfill lead to greater gas production.

In other parts of the world methane emissions from rice cultivation are a major concern because rice is grown on

flooded fields that produce anaerobic conditions to release methane. U.S. methane emissions from rice cultivation are

minimal because the United States is not a major producer of rice.

L. E. Chase, “Methane Emissions from Dairy Cattle,” Mitigating Air Emissions from Animal Feeding Operations

Conference, IA, May 2008, http://www.ag.iastate.edu/wastemgmt/Mitigation_Conference_proceedings/

CD_proceedings/Animal_Housing_Diet/Chase-Methane_Emissions.pdf.

For more information on anaerobic digestion systems, see CRS Report R40667, Anaerobic Digestion: Greenhouse

Gas Emission Reduction and Energy Generation, by (name redacted).

U.S. Environmental Protection Agency, 2010 U.S. Greenhouse Gas Inventory Report, EPA 430-R-10-006, April

2010, http://www.epa.gov/climatechange/emissions/usinventoryreport.html.

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Landfill gas is captured at the nation’s largest landfills.36 A 1996 Clean Air Act regulation known

as the “Landfill Gas Rule” established New Source Performance Standards and Guidelines that

require landfills with a 2.5 million metric ton design capacity that accepted waste after November

8, 1987, to capture and burn the gas. The gas can either be flared or used for energy production—

often it is used as fuel for electricity generation. As mentioned above, flaring is less damaging to

the atmosphere than release of the methane.

In promulgating the 1996 rule, EPA said that the 2.5 million metric ton minimum “corresponds to

cities greater than 100,000 people.” The agency also stated that the regulations “will only affect

less than 5 percent of all landfills” but would reduce emissions of methane by 37% at new

landfills, and by 39% at existing facilities.

In fact, partly as a result of tax incentives and voluntary programs, there are 541 operational

projects at landfills as of January 2011.37 This represents roughly 30% of the 1,812 municipal

solid waste landfills reported in operation in 2008.38

Whatever success existing regulations, tax incentives, and voluntary programs may be having, a

significant amount of methane continues to be emitted even at landfills subject to the Landfill Gas

Rule. In addition, there are few methane capture projects at smaller landfills and at landfills that

ceased operation before November 1987 (those not covered under the Clean Air Act). The latter

group, numbering in the tens of thousands of sites, poses a particular challenge. Often, there is no

responsible party who might implement a methane collection system if the site’s original owner is

no longer in business. At other sites (e.g., sites owned by local governments), there may be no

continuing stream of revenue to support installation and operation of the necessary equipment,

since the landfill has closed. Further barriers to additional landfill gas capture may include high

capital costs for equipment, low rates paid for the gas captured and/or electricity generated,

permitting requirements, and liability concerns.39

Oil and Natural Gas

Natural gas systems were the third-largest U.S. source of methane emissions in 2008. Methane

can be released from natural gas systems during normal operations, maintenance, and unexpected

system disorder. An array of technologies and suggested strategies to reduce methane emissions

from various stages of natural gas system production is available. 40

A common landfill gas capture system consist of an arrangement of vertical wells and horizontal collectors usually

installed after a landfill cell has been capped. Without a gas collection system, the landfill gas would escape into the

atmosphere.

Environmental Protection Agency, Landfill Methane Outreach Program , Energy Projects and Candidate Landfills,

http://www.epa.gov/lmop/projects-candidates/index.html.

Environmental Protection Agency, Municipal Solid Waste Generation, Recycling, and Disposal in the United States

Detailed Tables and Figures for 2008, November 2009, http://www.epa.gov/osw/nonhaz/municipal/pubs/

msw2008data.pdf.

Lenders may hesitate to provide funding for landfill gas capture projects due to unease about possibly having to

remediate a landfill under CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act; 42

USC 9607).

Environmental Protection Agency, Natural Gas STAR Program: Cost-Effective Opportunities to Recover Methane,

http://www.epa.gov/gasstar/basic-information/index.html#sources.

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Additionally, methane is emitted during oil production, transportation, and refining. Options to

reduce methane emissions from the oil sector include flaring, direct use, and reinjection of

methane into oil fields. Offshore oil operations (oil platforms) tend to use captured methane

directly because flaring is economically unattractive. Onshore oil operations usually inject the

captured methane into a pipeline. Captured methane can also be injected into an oil production

field to enhance future oil recovery. One analysis estimated the reduction efficiency (which is the

percentage reduction achieved with adoption of a mitigation option) for flaring, direct use, and

reinjection of methane to be 98%, 90%, and 95%, respectively.41 The equipment used for

abatement has a technical lifetime of 15 years.42 Barriers to methane capture from oil and natural

gas systems include federal and state economic regulations, financial constraints, abatement

technology cost, and abatement technology availability.

Coalbed Methane

The coal mining sector was the fourth-largest source of U.S. methane emissions in 2008.43 Most

methane emissions from coal mining occur during the mining process in underground mining

operations. The amount of methane released depends chiefly on the coal mine type (e.g.,

underground mine, surface mine, abandoned mine) and the mining operation type. Two

techniques are available to capture methane emissions from coal mines: degasification (including

enhanced degasification) and ventilation air methane systems.

A degasification system facilitates the removal of methane gas from a mine by ventilation and/or

by drainage. Methane is captured through a series of vertical wells, horizontal boreholes, or gob

wells drilled into the mine before or after mining operations.44 A sizeable portion of the methane

captured from degasification systems can be injected into a pipeline directly for energy purposes.

Enhanced degasification uses the same approach as degasification systems, but has the capacity to

extract lower-quality methane that must be cleaned and upgraded to meet “pipeline quality” gas

criteria. Ventilation air methane (VAM) systems flush air into underground mines to keep

methane concentration levels at or below 1%. VAM systems are necessary to provide safe

working environments for miners because methane can be explosive in low concentrations in air.

Methane captured from degasification systems has a higher methane concentration (30%-90%)

than methane captured from ventilation air systems.

Methane captured from coal mines using the methods described above can be used to generate

electricity on-site or for sale to utility companies. Of the estimated 9,294 coal mines (active

underground, active surface, and abandoned underground) in the United States, about 580 are

currently active underground coal mines, of which 50 have methane capture projects.45 Barriers to

methane capture from coal mines include legal issues, economic circumstances (e.g., high capital

costs for equipment, low electricity prices), restricted pipeline capacity for transporting coalbed

Environmental Protection Agency, Global Mitigation of Non-CO2 Greenhouse Gases, EPA 430-R-06-005, June

2006.

Technical lifetime is the length of time the equipment is expected to perform as intended.

U.S. Environmental Protection Agency, 2010 U.S. Greenhouse Gas Inventory Report, EPA 430-R-10-006, April

2010, http://www.epa.gov/climatechange/emissions/usinventoryreport.html.

A gob well allows for the extraction of methane from the gob area of a mine.

Environmental Protection Agency, Methane to Markets Partnership Country Specific Strategy for the United States,

October 2008, http://www.methanetomarkets.org/resources/coalmines/docs/coal_stratplan_us.pdf. Most of these coal

mines have been abandoned (8,000).

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methane from the mines to natural gas markets, and difficulties with technology development. A

primary barrier to methane recovery from coal mines is uncertainty regarding coalbed methane

ownership, which exists in part because coalbed methane is located in the same stratum as the

coal reserves, making a clear distinction for ownership difficult.46 Older leases may not clearly

specify whether the owner of the coal rights is also the owner of the coalbed methane. Ownership

may lie with the owner(s) of the coal rights, owner(s) of the oil and gas rights, or surface

owner(s). Ownership may also be an issue for federal lands in the West because developers of

federally owned coalbed methane must apply for a gas lease to implement a coal mine methane

project via competitive leasing procedures open to all.

Concerns Applicable to All Sources

Two impediments to methane capture cross-cut the top four anthropogenic sources of methane

emissions: pipeline capacity, and the price offered by the electric power industry for electricity

generated by captured methane. In addition to capacity, another issue is pipeline access for those

wanting to purchase captured methane but not immediately adjacent to the methane capture

source. In addition to price, other electricity industry issues of concern are competitiveness and

the sale of excess power generated from captured methane.

Federal Support for Methane Capture

Periodic reports to Congress from the executive branch, as well as hearing testimony, have

conveyed the significance of methane capture since the early 1990s.47 Congress and the executive

branch have supported methane capture projects through voluntary programs, energy

management programs, and research and development programs. This section highlights existing

efforts.

Methane-to-Markets Partnership

The Methane-to-Markets Partnership is an international initiative for methane capture and reuse

from four sources: oil and gas, coal mines, landfills, and agriculture.48 The partnership is

administered by the U.S. Environmental Protection Agency (EPA), which supports the voluntary

efforts of the 38 country partners. National governments, research institutions, and the private

sector have collaborated since 2004 to develop cost-effective, near-term methane capture projects

globally. The partnership receives its legal authority from the Clean Air Act, Section 103 (42

U.S.C. § 7403), and the National Environmental Policy Act (NEPA, 42 U.S.C. §§ 4321-4347).

Environmental Protection Agency, Coalbed Methane Extra: Coal Mine Methane Ownership Issues, EPA-430-N-00004, 2007, http://www.epa.gov/cmop/docs/fall_2007.pdf.

Environmental Protection Agency, Options for Reducing Methane Emissions Internationally, Volume 1:

Technological Options for Reducing Methane Emissions, EPA 430-R-93-006, July 1993; Environmental Protection

Agency, Opportunities to Reduce Methane Emissions in the United States Report to Congress, EPA 430-R-93-012,

October 1993. Nineteen hearings pertaining to methane have been held since 1990 including U.S. Congress, Senate

Committee on Environment and Public Works, hearing on S. 1772, Gas Petroleum Refiner Improvement and

Community Empowerment Act, 109th Cong., 1st sess., October 18, 2005, S.Hrg. 109-1001; and U.S. Congress, House

Committee on Science, Energy Research, Development, Demonstration, and Commercial Application Act of 2006,

109th Cong., 2nd sess., July 28, 2006, H.Rept. 109-611.

For more information on the Methane-to-Markets Partnership, visit http://www.globalmethane.org.

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Approximately $4.6 million was appropriated to the partnership for FY2010. Supplemental

funding for the partnership is received from the U.S. Department of State. Other U.S. government

partners—the Department of Energy, the Department of Agriculture, the Agency for International

Development, and the Trade and Development Agency—have the discretion to provide funds to

support the partnership. Financial support from government partners varies in amount and by

fiscal year.

Voluntary Methane Programs

EPA facilitates a number of voluntary programs related to the Methane-to-Markets initiative that

seek to reduce domestic methane emissions from different sectors. Many of these programs

receive broad legislative authority from the Clean Air Act, Section 103 (42 U.S.C. § 7403). EPA

provides some technical assistance and educational material. The AgSTAR Program supports

biogas capture and use at livestock operations managing liquid and slurry manures.49 The

Coalbed Methane Outreach Program (CMOP) works with the coalbed methane industry to reduce

coal mine methane emissions via methane capture and reuse. 50 The Natural Gas STAR Program

specializes in promoting the reduction of methane emissions from the oil production and natural

gas sector.51 The Landfill Methane Outreach Program (LMOP) encourages landfill gas energy

projects. 52 EPA’s domestic methane programs avoided the release of more than 20.3 million

metric tons of CO2e into the atmosphere in 2008, out of the roughly 308 million metric tons of

CO2e of the methane emissions reported for the landfills, natural gas systems, petroleum systems,

and coal mining categories. 53

Federal Energy Management Program

The Department of Energy’s (DOE’s) Federal Energy Management Program (FEMP) addresses

energy management at federal facilities and DOE, as well as fleet and transportation

management. 54 One component of the program is converting landfill gas to energy for use at

federal facilities. DOE has implemented three landfill gas recovery projects. FEMP receives its

legislative authority from the Energy Independence and Security Act of 2007 (P.L. 110-140) and

was appropriated $32 million for FY2010.

Tax Incentives

Several federal tax incentives subsidize methane capture from landfill and agriculture sources.

These tax incentives are broadly broken down into three categories: (1) incentives to produce

For more information on the AgSTAR Program, see http://www.epa.gov/agstar.

For more information on the Coalbed Methane Outreach Program, see http://www.epa.gov/cmop/index.html.

For more information on the Natural Gas STAR Program, see http://www.epa.gov/gasstar/index.html.

For more information on the Landfill Methane Outreach program, see http://www.epa.gov/lmop.

AgSTAR Program reduced methane emissions—not available. However, the program has provided technical

assistance for over 150 operational anaerobic digestion systems. Environmental Protection Agency, ENERGY STAR

and Other Climate Protection Partnerships 2008 Annual Report, December 2009, http://www.epa.gov/appdstar/pdf/

2008AnnualReportFinal.pdf; U.S. Environmental Protection Agency, 2010 U.S. Greenhouse Gas Inventory Report,

EPA 430-R-10-006, April 2010, http://www.epa.gov/climatechange/emissions/usinventoryreport.html..

For more information on the Federal Energy Management Program, see http://www1.eere.energy.gov/femp.

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electricity from captured methane gas; (2) incentives to build facilities that produce electricity

from captured methane gas; and (3) incentives to produce alternative fuels using captured

methane gas.

Two federal tax incentives subsidize the production of electricity from methane. The production

tax credit is allowed for the production of electricity from qualified energy resources at qualified

facilities, including open-loop biomass and municipal solid waste facilities. 55 In general, openloop biomass and municipal solid waste facilities placed in service after August 8, 2005, and

before December 31, 2013, may claim a tax credit equal to 1 cent per kilowatt-hour of electricity

generated during the first 10 years of production.56 In addition, a one-time investment tax credit

equal to 30% of eligible investment costs is available, in lieu of the production tax credit, for

open-loop biomass and municipal solid waste facilities placed in service after December 31,

2008.57 In addition, the American Recovery and Reinvestment Act of 2009 (ARRA, P.L. 111-5)

allowed a grant in lieu of tax credits for property placed in service in 2009 and 2010.

Three tax-preferred bond finance options exist to help finance methane capture facilities used to

produce electricity. Qualified Energy Conservation Bonds (QECBs), Clean Renewable Energy

Bonds (CREBs), and New Clean Renewable Energy Bonds (New CREBs) are a type of bond

instrument, tax credit bonds, that offers the holder a federal tax credit instead of interest.58 The

rate of credit for CREBs is intended to be set such that the bonds need not be sold at a discount

(for a price less than the face value) or with interest costs to the issuer, while the credit rate for

QECBs and New CREBs is set for a credit rate of 70%. All three bond options are available to

finance qualified energy production projects, including open-loop biomass facilities and landfill

gas facilities. QECBs, CREBs, and New CREBs are all subject to national limits, $2.4 billion,

$1.2 billion, and $2.4 billion, respectively. CREBs and New CREBs are allocated by the

Secretary of the Treasury to eligible projects in inverse to their size, while QECBs are allocated to

the states based upon their share of total U.S. population. Issuing authority for QECBs is without

expiration, while CREB and New CREB authority expired at the end of 2009.

In addition, two tax incentives are available where methane gas is used to as a production input

for alternative fuels. Facilities with binding construction contracts in place before December 31,

2010, and placed in service before January 1, 2014, are eligible to expense one-half of the cost of

qualified property in the facilities first year of service. 59 The remaining 50% of the cost is

depreciated under an accelerated five-year depreciation period. Further, compressed or liquefied

gas and liquid fuel derived from biomass is eligible for the $1.00 per gallon alternative fuel tax

credit for fuel produced through December 31, 2011.60

Internal Revenue Code (I.R.C.) Section 45. Municipal solid waste covers two types of power facilities: trash

combustion facilities that burn trash directly to generate power, and landfill gas facilities that first produce methane,

which is then burned to generate electricity. Anaerobic digestion systems are an example of an open-loop biomass

system.

The credit rate is adjusted each year for inflation. In addition, facilities placed in service prior to August 8, 2005, may

claim the credit for the first five years of production. Further, the date in service break-point for certain open-loop

biomass facilities is October 22, 2004.

I.R.C. Section 48.

Qualified Energy Conservation Bonds (QECBs), Clean Renewable Energy Bonds (CREBs) and New Clean

Renewable Energy Bonds (New CREBs) are defined in I.R.C. Sections 54D, 54C and 54, respectively. See CRS Report

R40523, Tax Credit Bonds: Overview and Analysis, by (name redacted), for more information on tax credit bonds.

I.R.C. Section 179C.

I.R.C. Section 45K.

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DOE Methane Hydrate Research and Development

Methane is not captured from naturally occurring gas hydrates because it is bound in the gas and

not released. However, recent attention has been directed toward the extraction of methane from

gas hydrates as a potential source of energy.61 The objective of the DOE methane hydrate research

and development program is to develop knowledge and technology to allow commercial

production of methane from gas hydrates by 2015. The DOE program completed a Gulf of

Mexico offshore expedition in May 2009 aimed at validating techniques for locating and

assessing commercially viable gas hydrate deposits.62 The program is planning a two-year

production test in Alaska that is expected to provide critical information about methane flow rates

and sediment stability during gas hydrate dissociation. Both projects have international and

industry partners. Methane hydrate research by DOE was initially authorized by the Methane

Hydrate Research and Development Act of 2000 (P.L. 106-193). The Energy Policy Act of 2005

(P.L. 109-58, Subtitle F, § 968) extended the authorization through FY2010 and authorized total

appropriations of $155 million over a five-year period. The Omnibus Appropriations Act, 2009

(P.L. 111-8), provided $20 million in FY2009 for natural gas technologies R&D, to include no

less than $15 million for gas hydrates R&D. Congress appropriated $15 million for the gas

hydrate R&D program in FY2009. The Obama Administration requested $25 million for the

natural gas technologies program for FY2010, which includes gas hydrate R&D. Congress

appropriated $17.8 million for the program in FY2010, which would also fund research and

development into unconventional gas production from basins containing tight gas sands, shale

gas, and coal bed methane, as well as for gas hydrates.

Methane hydrates—a mixture of water and natural gas—are a potentially huge global energy resource. For more

information on the DOE methane hydrate R&D program, see CRS Report RS22990, Gas Hydrates: Resource and

Hazard, by (name redacted); and http://www.netl.doe.

gov/technologies/oil-gas/FutureSupply/MethaneHydrates/rdprogram/rd-program.htm.

On May 6, 2009, DOE announced it had completed a 21-day drilling expedition in the Gulf of Mexico in

collaboration with the USGS and the Minerals Management Service. A preliminary announcement of the expedition

results is available at http://www.netl.doe.gov/technologies/oil-gas/FutureSupply/MethaneHydrates/2009GOMJIP/

GOMJIP_Leg2Announcement.html.

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Appendix. World Methane Emissions by Sector in

2005

Source: Climate Analysis Indicators Tool (CAIT) Version 6.0 (Washington, DC: World Resources Institute, 2009).

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Author Contact Information

(name redacted)

Analyst in Agricultural Conservation and Natural

Resources Policy

#redacted#@crs.loc.gov, 7-....

(name redacted)

Specialist in Energy and Natural Resources Policy

#redacted#@crs.loc.gov, 7-....

(name redacted)

Specialist in Environmental Policy

#redacted#@crs.loc.g

ov, 7-....

(name redacted)

Section Research Manager

#redacted#@crs.loc.gov, 7-....

(name redacted)

Specialist in Environmental Policy

#redacted#@crs.loc.gov, 7-....

Congressional Research Service

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