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![handle is hein.crs/govefnj0001 and id is 1 raw text is: Congressional Research Service
Inforrning the legislative debate since 1914
0
April 1, 2022
Advances in Satellite Methane Measurement: Implications for
Fossil Fuel Industry Emissions Detection and Climate Policy
On November 15, 2021, under the authority of Section 111
of the Clean Air Act, the U.S. Environmental Protection
Agency (EPA) published a rulemaking that proposes
comprehensive standards of performance for GHG
[greenhouse gas] emissions (in the form of methane
limitations) ... for new, modified, and reconstructed sources
in the Crude Oil and Natural Gas source category, including
the production, processing, transmission and storage
segments (86 Federal Register 63110, November 15,
2021). Lessening unintended emissions known as fugitive
emissions is one set of actions in this proposal to constrain
large emissions sources known as super-emitters. The
rulemaking requests both information and comments on
alternative measurement technologies for methane
emissions, especially those attributed to super-emitters. The
EPA is seeking input on technologies that could distinguish
large emission events and a definitional emissions level for
designating an event as large. It is specified in the
rulemaking that any emissions visible by satellites should
qualify as large emission events (86 Federal Register
63110, November 15, 2021). The role of evolving satellite
technologies that have the ability to monitor methane and
contribute to the identification of large emission events is
discussed here.
Background on Methane Emissions
Fossil-fuel-related industries emit methane into the
atmosphere. Methane has a global warming potential 28
times greater than carbon dioxide over a 100-year period. It
is second only to carbon dioxide in contributions to global
temperature increases from human emissions of greenhouse
gases. It has been estimated for the United States that
approximately 30% of methane emissions from onshore oil
and gas production arise from fugitive emissions, while
such emissions are approximately 1.8 times greater than
emissions from venting for pipelines and liquefied natural
gas facilities.
Fugitive emissions are generally described as leaks from
pressure containment systems, which can include leaks
from valves or flanges, in fossil fuel facilities. Fugitive
emissions also include methane that escapes to the
atmosphere from incomplete combustion during flaring
(burning of excess gas). A small number of fugitive
emission events, known as super-emitters, account for
approximately 50% of fugitive emissions in the fossil fuel
sector and are sourced from approximately 5% of fugitive
emission events. Locating, identifying, and attributing these
events to specific sources is critical to reducing methane
emissions overall.
Reducing fugitive methane emissions, including super-
emitter events, is believed by some to be important for
achieving climate change mitigation and public health
goals. Measuring methane emissions on a large scale is
difficult, and the measurement technologies continue to
evolve (see CRS In Focus IF10752, Methane Emissions: A
Primer, by Richard K. Lattanzio).
Advances in remote sensing of methane from satellites may
improve monitoring and detection of emissions from oil,
coal, and natural gas operations. Improving the
measurement of these methane emissions can contribute to
the U.S. effort to meet treaty obligations under the United
Nations Framework Convention on Climate Change
(UNFCCC). These obligations include emissions reporting
requirements as well as scientific and technical cooperation
(see CRS Report R40001, A U.S.-Centric Chronology of the
United Nations Framework Convention on Climate
Change).
Methane Monitoring Strategies
There are two general categories for methane monitoring.
One method, sometimes referred to as bottom up (BU),
extrapolates measurements from individual components.
BU methods rely on averaging numerous leak test
measurements of industry components to develop
emissions factors that are aggregated and used to estimate
emissions, based on the number of facilities and the levels
of production. However, because emissions factors are
based primarily on leakage measured under normal
conditions, they may not fully account for abnormal super-
emitter events. As a result, BU methods may understate
total emissions.
Emerging technologies may enhance the second type of
monitoring strategy. Referred to as top down (TD), these
methods provide direct empirical measurements of
methane, not estimates based on emissions factors, at
specific locations. Using either ground-based instruments or
those on aircraft or satellites, methane emissions may be
measured directly. The downsides of TD are relative cost,
and coverage limitations. Satellites and aircraft
measurements cost more than computer model estimates
extrapolated from limited sampling during normal
operation. Also, some of these TD methods typically occur
only at infrequent intervals, and may miss detection of
sporadic emission events. As technologies mature, costs
may drop. Increasing satellite sampling frequency offers an
opportunity to improve accuracy and precision.
Satellite Measurement of Methane
Emissions
Satellite detection methods can involve tradeoffs that may
allow some fugitive emissions to go undetected. These may
be addressed as technical capabilities improve and datasets
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