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Methane (CH4) is the second-most-abundant anthropogenic (human-created) greenhouse gas and significantly contributes to global warming. Consequently, there is an urgent need to reduce methane emissions to help reduce temperature increases from anthropogenic greenhouse gases. An essential part of any strategy to mitigate methane emissions is the ability to accurately measure and monitor the amount and location of methane released by various sectors. This report identifies several policy recommendations that can substantially enhance the detection of methane released by the oil and gas sector. These recommendations could strengthen measures already taken by that sector to manage methane and enhance worker safety.
The atmospheric concentration of methane has risen rapidly since the start of the industrial revolution in the 18th century, from 730 parts per billion (ppb) in 1750 to 1866 ppb in 2019, due primarily to human activities. The recent increases in methane concentrations appear to be equally contributed by the fossil-fuel sector and by a combined contribution from agricultural activity and waste sources.
Quantifying emissions from the fossil-fuel sector has led to three consequences. First, companies that are losing a valuable commodity to the atmosphere have begun using the latest technology for leak detection and repair (LDAR). Second, with the global community moving toward regulation of greenhouse gas emissions, the question of how to verify emission decreases from the oil and gas industry has arisen. Lastly, the scientific community has started to form a picture of how these emissions are distributed and how different components, sites, and processes contribute. It has become clear that a small portion of methane sources (such as leaks) are contributing a significant fraction of the total emitted natural gas. Identifying and mitigating these large leaks quickly can potentially reduce production costs while alleviating a large percentage of the emission problem.
For methane emission regulation to be most effective, it should specifically target the small portion of leaks that are major emitters. Additionally, data should be publicly available and with high enough spatial resolution to determine the source of the emissions, especially in regions where well pads owned by different companies are spatially collocated. Domestically, ground and aircraft measurements offer sensitive and cost-effective approaches for frequent or continuous monitoring of individual assets. At the same time, limiting methane emissions will need to be done globally. Satellite measurements are uniquely capable of supporting international collaborations to identify significant sources worldwide and informing international agreements to mitigate emissions.
Three scientific and technological advances across several fields would appreciably improve our ability to measure and monitor methane emissions. The first would be the construction of improved high-resolution spectroscopic databases for methane, especially for its near-infrared spectral bands commonly used for remote sensing. The second would be the invention of improved methods for remote sensing of carbon isotopes, which would greatly facilitate identifying fuel source type. The third would be the development of high quantum efficiency detectors to support methane LIDAR (light detection and ranging instruments), which would be particularly advantageous for resolving the three-dimensional distribution of methane in the Earth’s atmosphere.
To support emerging national and international efforts to mitigate emissions of methane, three areas of policy development would be beneficial:
Methane emissions detection:
Reliable and systematized data and models to support mitigation measures:
This report is deliberately focused on methane emissions from oil and natural gas operations. While agriculture and agricultural waste constitute the dominant sources of emissions worldwide, the measures to mitigate emissions from agricultural and fossil-fuel sectors can be quite different. The authors also recognize that the methane emissions from the leaks in the US oil and gas supply chain are as much as 60% higher than official inventory estimates. However, to focus on emissions that can be readily addressed by targeted measures at significant point sources, this study is intentionally delimited to methane released to the atmosphere from the production of fossil fuels.