In a new study measuring methane pollution at hundreds of landfills across the United States, scientists have discovered that the problem of garbage piling up in landfills is even more detrimental to the climate than previously thought. The study, which conducted the largest measurement-based survey of American landfills between 2018 and 2022, revealed that average methane emissions from landfills are significantly higher than the figures officially reported.

Methane, a potent greenhouse gas with over 80 times more warming power than carbon dioxide in the near-term, is produced by various sources including oil and gas, as well as agriculture. While landfills are considered a less well-known methane source, they have a substantial impact, estimated at around 20% of global human-caused methane emissions. This occurs when organic waste such as food scraps, paper, and wood decomposes without oxygen, creating the optimal environment for methane-producing bacteria.

The majority of landfills in the United States are required to measure methane emissions four times a year using handheld sensors during walking surveys. However, the accuracy of these surveys can vary as individuals tend to avoid unsafe areas such as steep slopes and actively dumping zones. According to Daniel Cusworth, lead author and scientist with the non-profit Carbon Mapper, these measurements are not designed to effectively measure emissions but rather detect methane "hotspots."

To address potential gaps in data, the study highlights the importance of advanced monitoring systems that utilize remote sensing from aircraft, drones, and satellites. It was through airborne imaging spectrometers, employed by the scientists in this study, that they detected methane plumes at 52% of the measured landfills. This detection rate surpasses that of airborne studies conducted for the oil and gas sector.

The results of the study indicate that current reporting systems, such as the Environmental Protection Agency's Greenhouse Gas Reporting Program (GHGRP), are underestimating methane emissions from landfills. The average methane emission rates from landfills were found to be 1.4 times higher than those officially reported to the GHGRP.

Furthermore, the study discovered that landfill methane emissions are often more persistent compared to those from oil and gas production. Around 60% of measured emissions lasted for multiple months or even years, underscoring the significance of addressing this issue promptly.

Commenting on the findings, Rob Jackson, a professor of environmental science at Stanford University, emphasized that landfills are significant "super-emitters" of methane. He stated that the airborne data obtained in this study align with what has been observed on the ground for many years.

Unfortunately, the impact of landfills is expected to persist as waste generation remains an ongoing issue even in a future less reliant on fossil fuels. Scientists stress that reducing methane emissions swiftly is crucial in combating climate change due to its potent short-term warming impact. However, current methane policies in the United States primarily target the oil and gas industry. To effectively meet climate targets, Cusworth suggests that landfills should receive similar attention and focus as the oil and gas sector.

As the study sheds light on the alarming levels of methane emissions from landfills, it calls for a reevaluation of waste management strategies and emphasizes the urgent need to incorporate robust mitigation efforts for this substantial contributor to climate change.