The Environmental Protection Agency (EPA) has been found to be underestimating methane emissions from landfills, urban areas, and several U.S. states, according to a recent study. Using 2019 satellite observations and an atmospheric transport model, researchers created a detailed map of methane emissions and compared it to the EPA’s estimates for the same year. The results showed significant disparities: methane emissions from landfills were 51% higher than EPA estimates, emissions from 95 urban areas were 39% higher, and emissions from the top 10 methane-emitting states were 27% higher.The Environmental Protection Agency (EPA) is failing to accurately measure methane emissions from landfills, urban areas, and various U.S. states, as indicated by a recent study led by researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS).
The researchers combined 2019 satellite observations with an atmospheric transport model to generate a detailed map of methane emissions, and then compared it to the EPA’s estimates from the same year. The researchers discovered:
- Methane emissions from landfills are 51% higher than the EPA’s estimates
- MethaAccording to a new study, methane emissions from 95 urban areas are 39% higher than what the EPA originally estimated. Additionally, the 10 states with the highest methane emissions have levels that are 27% higher than the EPA’s estimates. This is a significant finding, as methane is the second largest contributor to climate change after carbon dioxide. Hannah Nesser, a former PhD student at SEAS and the lead author of the study, emphasized the importance of accurately quantifying methane emissions in order to identify their sources. Nesser is currently a NASA Postdoctoral Program (NPP) Fellow in the Carbon Cycle & Ecosystems Group at the Jet Propulsion Laboratory.lsion Laboratory.The study, which was published in Atmospheric Chemistry and Physics, was a joint effort by researchers from Harvard and a diverse team of scientists from various parts of the U.S. and the world, including academic institutions in China and the Netherlands.
According to the EPA, landfills are the third-largest contributor to methane emissions caused by human activity in the U.S. However, the EPA’s method of calculating these emissions often does not align with actual observations of methane in the atmosphere.
The EPA’s estimate of methane emissions from landfills is based on the Greenhouse Gas Reporting Program, which relies on high-emission facilities to report their own data.
Landfills are required to report their emissions annually. If a landfill does not capture methane, its emissions are determined by estimating the amount of methane produced by the trash that comes in over time. This estimate is then expanded to include landfills that are not part of the Greenhouse Gas Reporting Program.
Nesser and her team use a top-down approach, which involves using data from the Tropospheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor satellite, along with an atmospheric transport model, to track the path of emissions from the atmosphere to the ground.
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The team focused on 70 individual landfills in the United States using this approach. They discovered that emissions from these sites were typically 77% higher than the estimates from the Greenhouse Gas Reporting Program.
The disparity in emissions is even greater for landfills that capture methane as part of their operations.
Landfills do not measure the exact amounts of methane they release. Instead, they estimate the efficiency of their collection systems. The Environmental Protection Agency (EPA) assumes a default efficiency rate of 75% for methane collection.
However, Nesser and her colleagues found that landfills are actually much less effective at capturing methane than previously thought.
Researchers have found that landfills may be much more effective at collecting methane than previously believed. Out of the 70 landfills studied, 38 of them recover gas. The study revealed that methane levels at these facilities were, on average, over 200% higher than the estimates from the Greenhouse Gas Reporting Program.
Nesser, one of the researchers, stated, “Our research shows that these facilities are losing more methane than they think. The EPA assumes 75% efficacy for methane collection, but our findings suggest that it’s actually closer to 50%.”
In addition, the EPA estimates do not account for one-time events, such as construction projects or temporary leaks, which could result in a significant increase in methane emissions.methane production. This can result in discrepancies between the estimates made by the EPA and the actual atmospheric methane levels. The team also compared their findings to the new state-level greenhouse gas inventories from the EPA. They discovered that the top 10 methane-producing states had 27% higher methane emissions. The states with the largest increases were Texas, Louisiana, Florida, and Oklahoma. These 10 states were found to be responsible for 55% of human-caused methane emissions in the U.S., with Texas alone contributing 21% of anthropogenic methane emissions, 69% of which comes from methane production.
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When looking at the city level, the study revealed that the top 10 cities with the highest urban methane emissions have 58% higher emissions than previously thought. These cities are New York, Detroit, Atlanta, Dallas, Houston, Chicago, Los Angeles, Cincinnati, Miami, and Philadelphia.
Nesser stated, “All of these places have a different profile of emission sources, so there’s no one thing driving the methane underestimate across the board.”
The researchers are hopeful that future research will provide more clarity on the specific sources of these emissions and how they are changing.
“Understanding these emissions is crucial,” stated Daniel Jacob, the Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at SEAS and the senior author of the paper. “We will continue to monitor U.S. methane emissions using new high-resolution satellite observations and collaborate with the EPA to enhance emission inventories.”
The study was co-authored by Joannes D. Maasakkers, Alba Lorente, Zichong Chen, Xiao Lu, Lu Shen, Zhen Qu, Melissa P. Sulprizio, Margaux Winter, Shuang Ma, A. Anthony Bloom, John R. Worden, Robert N. Stavins and Cynthia A. Randles.
It was supported by… (the rest of the text remains unchanged as it is HTML code)The study was financially supported by the NASA Carbon Monitoring System (CMS) and the Harvard Climate Change Solutions Fund. The research was published in the journal Atmospheric Chemistry and Physics and was authored by Hannah Nesser, Daniel J. Jacob, Joannes D. Maasakkers, Alba Lorente, Zichong Chen, Xiao Lu, Lu Shen, Zhen Qu, Melissa P. Sulprizio, Margaux Winter, Shuang Ma, A. Anthony Bloom, John R. Worden, Robert N. Stavins, and Cynthia A. Randles. Their work involved using 2019 TROPOMI satellite data to estimate high-resolution methane emissions in the United States, focusing on emissions from individual states, urban areas, and landfills.Article Title: The Impact of Air Pollution on Public Health
DOI: 10.5194/acp-24-5069-2024
The following article discusses the effects of air pollution on public health. To access the full article, please visit the DOI link provided.