Updated August 23, 2018
Methane Emissions: A Primer
Methane is the world’s simplest hydrocarbon, with a
Methane: Pollutant
chemical formula CH4 (one atom of carbon and four atoms
Methane, however, when released or allowed to escape into
of hydrogen). It is gaseous under normal atmospheric
the atmosphere (commonly referred to as “vented” and
conditions and is commonly produced through the
“fugitive” emissions, respectively), can affect human health
decomposition of organic materials in the absence of
and safety and the environment. The U.S. Occupational
oxygen. It is released into the atmosphere by natural
Safety and Health Administration lists methane as both an
sources such as wetlands, oceans, sediments, termites,
asphyxiant and an explosive, as increased concentrations in
volcanoes, and wildfires as well as human activities such as
local settings can jeopardize worker safety. Further, the
oil and natural gas systems, coal mines, landfills,
U.S. Environmental Protection Agency (EPA) classifies
wastewater treatment facilities, and the raising of livestock.
methane as both a precursor to ground-level ozone
formation (commonly referred to as “smog”) and a potent
Methane: Fuel and Chemical Feedstock
greenhouse gas (GHG), albeit with a shorter atmospheric
Methane is the primary component of natural gas. When
life than CO2. Methane’s effect on climate change is up to
extracted from geologic formations or captured by other
34 times greater than that of CO2 when averaged over a
means, it can be used as either a fuel or a chemical
100-year time period and even greater when considered
feedstock.
over the first 20 years after it is emitted. Arguably, any
increase in methane emissions may counteract some of the
When used as a fuel, methane has many advantages over
environmental benefits that the U.S. economy has to gain
other hydrocarbons (e.g., coal and oil). Methane is more
by switching from coal or oil to natural gas. For these
versatile: It can heat homes, fuel stoves, run vehicles, fire
reasons, the Obama Administration proposed and
power plants, and be exported to support the energy needs
promulgated several regulations to control for emissions.
of U.S. trading partners. Methane is cleaner-burning: It
Under the Trump Administration, federal agencies are in
emits, on average, about half as much carbon dioxide (CO2)
the process of reconsidering these rulemakings.
as coal and one-quarter less than oil, per unit of energy,
when consumed in a typical electric utility plant. Further,
Generally, air pollution regulations compete against the
its combustion emits no mercury (a persistent, bio-
economic considerations of affected industries. In
accumulative neurotoxin), virtually no particulate matter or
methane’s case, however, its dual nature as both a
sulfur dioxide, and less nitrogen oxides, per unit of energy,
commodity and a pollutant provides a unique set of
than either coal or oil. Recent expansion of natural gas
incentives. Under certain conditions, the value of fugitive
production—primarily as a result of improved technologies
methane and other byproducts that can be recovered and
(e.g., hydraulic fracturing and directional drilling) used on
sold at market may be able to offset the cost of their
unconventional resources (e.g., shale, tight sands, and
capture. Further, the value of these recovered products
coalbed methane)—has made methane an increasingly
during oil and gas extraction can contribute to increased
significant component in the energy supply and security of
royalty payments to state and federal governments.
the United States.
The difficulty, however, is that methane emissions are not
When used as a chemical feedstock, methane is a
always easy to capture. Methane, unlike some other
manufacturing component for a variety of household and
pollutants (e.g., sulfur dioxide or CO2), is not commonly
industrial products including plastic, fertilizer, antifreeze,
emitted in a concentrated stream from industrial processes.
and fabrics. Abundant and economical supplies of methane
Rather, it is released into the atmosphere through
may arguably serve to reinvigorate the U.S. petrochemical
dispersion, leaks, vents, accidents, and ruptures. In this
sector, bringing manufacturing industries back on shore and
way, methane emissions are most similar to those of other
aiding in the creation of domestic jobs and economic
volatile organic compounds (VOCs), both in manner and
development.
control. Efforts to monitor, capture, or abate these
emissions are generally more difficult and costly than for
For these reasons, many have advocated for the increased
other pollutants. Whether recovery of methane is profitable
production and use of methane (via natural gas extraction or
for producers may depend upon a number of factors,
other capture technologies) and have hailed it as a potential
including the nature and extent of the release, the
“cost-effective bridge” to a less polluting and lower
technology available for capture, and the market price for
greenhouse-gas-intensive economy. This position has been
the recovered products. In this way, the cost-benefit
supported by many Members of Congress as well as recent
consideration of methane capture becomes similar to that of
Administrations.
energy efficiency efforts wherein high up-front investments
and other market barriers have the potential to be offset
over time.
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Methane Emissions: A Primer
Methane Emissions
Issues for Congress
According to EPA, methane is the second-most prevalent
Through the years, the federal government has sought
GHG emitted in the United States (behind CO2), and in
policies (both legislative and regulatory) to control methane
2016—the latest year of available data—it accounted for
emissions for a variety of economic, environmental, public
657 million metric tons of CO2 equivalent, or about 10% of
health, and safety reasons, including:
all domestically produced GHG emissions from human
activities. Some studies have put these emissions higher. Of
Promoting domestic energy production and security,
the total, 43% was emitted from sources in the energy and
Protecting the property rights of mineral owners
industrial sector, 38% from sources in the agricultural
(including federal resources and associated royalties to
sector, and 19% from sources in the waste sector.
the American taxpayer),
Assuring the operational safety of employees who work
Between 1990 and 2016, U.S. methane emissions decreased
with or near significant emission sources, and
by a little over 16%. Still, trends have fluctuated over the
Safeguarding the general population from air pollution.
past decade, with increases reported in some years. Since
1990, emissions from sources associated with agriculture
Under President Obama, federal activities in support of
have increased, while emissions from sources associated
methane emission reductions became one of the
with waste management, energy, and industrial processes
cornerstones of his “Climate Action Plan.” In the
have decreased (see Figure 1).
Administration’s 2014 “Strategy to Reduce Methane
Emissions,” a number of federal agencies proposed and
Economic and technical difficulties have made a
promulgated a suite of voluntary and regulatory programs
comprehensive national inventory of methane emissions
to address methane emissions, including:
difficult to attain. Unlike CO2, whose emissions are
reported using well-tracked energy statistics, methane is
A joint Department of Agriculture, Department of
emitted to the atmosphere primarily through fugitive
Energy, and EPA “Biogas Roadmap” outlining
releases. By definition, fugitive emissions are diffuse,
voluntary strategies in the agricultural sector (released
transitory, and elusive. Thus, one of the greater difficulties
on August 1, 2014).
in understanding the impacts of methane emissions is
EPA standards to reduce methane emissions from new
acquiring comprehensive and consistent observational data.
and modified activities and equipment in the oil and
For this reason, methodologies for measuring methane
natural gas sector (promulgated on June 3, 2016).
emissions are under near-constant revision.
EPA standards to reduce methane emissions from new
and existing municipal solid waste landfills
Figure 1. U.S. Methane Emissions: Historical Trends
(promulgated on August 29, 2016).
Bureau of Land Management (BLM) standards to
reduce venting and flaring from oil and gas production
on public lands (promulgated on November 18, 2016).
Some stakeholders raise concerns over federal controls.
They argue that more stringent standards on methane
emissions would not provide cost-effective health and
environmental benefits. Some industries contend that they
are already doing everything feasible to capture and reuse
methane emissions (for economic and safety reasons).
Others note that state and local authorities—who may share
a closer understanding of the industries’ specific
circumstances—are better equipped to oversee and enforce
emission reduction efforts. Some states (e.g., Colorado,
California, Ohio, Wyoming, and Pennsylvania) have
emissions standards for their energy industries.
President Trump—in a direct response to the Obama-era
standards and in line with his campaign promises—signed
Executive Order 13783 on March 28, 2017. The order
requires agencies to review existing regulations and
“appropriately suspend, revise, or rescind those that unduly
burden” domestic energy production and use. As a result,
EPA’s landfill, oil, and natural gas sector standards and
BLM’s venting and flaring rule are under reconsideration.
The federal court system is currently reviewing several
provisions in the Obama-era standards as well as the
suspension actions taken during the Trump Administration.
Source: CRS, with data from the U.S. Environmental Protection
Agency, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-
2016, EPA 430-R-18-003, April 12, 2018.
Richard K. Lattanzio, Specialist in Environmental Policy
IF10752
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Methane Emissions: A Primer
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