April 13, 2024

Study finds point source emissions from landfills have an outsized impact and present an opportunity to combat residual methane in the U.S.

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Methane plumes observed by Carbon Mapper during aerial surveys at a landfill in Georgia. Credit: Carbon Mapper

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Methane plumes observed by Carbon Mapper during aerial surveys at a landfill in Georgia. Credit: Carbon Mapper

A new study, led by Carbon Mapper scientists along with researchers from NASA’s Jet Propulsion Laboratory, Arizona State University, the University of Arizona, Science Aviation and the U.S. Environmental Protection Agency, provides the largest comprehensive assessment yet. of hundreds of US landfills using direct airborne observations. researches.

The study, published in the journal Science, reveals the outsized impact of point source emissions from landfills, which are responsible for a disproportionately large share of the pollution coming from this important sector. It also illuminates potential gaps in traditional model-based emissions accounting methods that can benefit from sustained direct measurement using emerging surface-, air-, and space-based monitoring technologies.

“Addressing these elevated sources of methane and mitigating persistent landfill emissions offers strong potential for climate benefits,” said Dr. Dan Cusworth, Carbon Mapper program scientist and lead author of the paper.

“The ability to accurately identify leaks is an efficient way to make rapid progress in reducing methane in landfills, which could be critical to slowing global warming.”

Landfills are considered the third largest source of human-caused methane emissions in the U.S., responsible for 14.3% of methane in 2021 and emitting the equivalent of greenhouse gas (GHG) emissions of nearly 23.1 million gasoline-powered passenger vehicles driven in a year, according to the EPA.

Despite the climate impact of landfills, societal understanding of these emissions is largely limited to model-based estimates, and the sector remains under-addressed compared to other major sources of methane such as oil and gas. Traditional surface-based surveys with portable methane sensors provide an incomplete picture of emissions. This is due to factors such as limited access to many sections of active landfills, as well as logistical and personal safety reasons.

To help fill these gaps, Carbon Mapper and research partners used advanced aircraft to conduct the largest direct measurement-based survey of active municipal solid waste landfills to date, from 2018 to 2022. This included aerial surveys, led by Carbon Mapper and by Scientific Aviation, from more than 200 active landfills in the US that participate in the US Greenhouse Gas Reporting Program (20% of approximately 1,200 open landfills reported). Research led by Carbon Mapper utilized partner aircraft – including NASA JPL’s AVIRIS-NG and Arizona State University’s Global Airborne Observatory with the Center for Global Discovery and Conservation Science.

Key Takeaways

Assessment of this large data set has produced knowledge that site owners and operators, policymakers, regulators, and civil society can use to better assess and act on landfill emissions.

  • Point source emissions from landfills have an outsized methane impact: 52% of landfills surveyed had observable point source emissions. This far exceeds the 0.2% to 1% detection rate observed for super emitters from oil and gas infrastructure surveyed in California and the Permian Basin.
  • Point source emissions from landfills are generally more persistent compared to their counterparts in oil and gas production: For landfills with observed emissions, 60% had emissions that persisted for months or years. These persistent emissions totaled 87% of all emissions quantified in the study. Comparatively, most methane super-emitters in the oil and gas sector are related to irregular and short-lived events.
  • There are significant gaps in landfill leak detection and quantification protocols: Current on-foot surveys with portable sensors are ineffective at fully sampling the landfill surface and may miss point source activities that can dominate facility emissions and remain undetected for long periods. Advanced monitoring strategies, such as remote sensing from satellites, aircraft and drones, can provide a more accurate picture of methane emissions from landfills. When combined with improved ground-based measurements, remote sensing can provide consistent, comprehensive measurements to better inform models, guide mitigation efforts, and verify emissions reductions.
  • A robust data set of quantified emissions from U.S. landfills finds little agreement with national reporting frameworks: a misalignment between observed and reported emissions indicates that current methods used to report facility emissions, such as the EPA Greenhouse Gas Reports (GHGRP) are missing or misrepresented. large sources of methane. On average, air emission rates were 1.4 times higher than those of the GHGRP. This presents a significant difference between observed and reported emissions, supported by the largest aerial or ground survey of US landfills to date.

Looking to the future, this study reveals the need for a comprehensive monitoring strategy to more effectively measure, quantify and act on landfill methane emissions. Resources like the Carbon Mapper Coalition satellite program can offer efficient solutions to measurement challenges. The coalition’s first Tanager satellite, which will launch in 2024 as part of a public-private partnership between Carbon Mapper, Planet Labs PBC, NASA JPL and others, is designed and optimized exclusively to detect methane in landfills.

Carbon Mapper is also leading a multi-year initiative to assess thousands of high-emission solid waste sites around the world, using remote sensing technologies to establish a methane emissions baseline for managed landfills and unmanaged landfills. This includes aerial campaigns at landfills in the US planned for 2024.

Carbon Mapper’s methane data is publicly available on its portal to maximize the availability of emissions data for a wide range of operators in many jurisdictions, including large waste management companies and local city and county governments. This helps empower them to mitigate emissions and make informed decisions that maximize methane capture. Data is also made available to policymakers, regulators, community groups and others to support science-based decision making.

More information:
Daniel H. Cusworth, Quantifying Methane Emissions from United States Landfills, Science (2024). DOI: 10.1126/science.adi7735. www.science.org/doi/10.1126/science.adi7735

Diary information:
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Provided by Carbon Mapper

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