Aerial observations identify major sources of U.S. landfill methane emissions

Through tests from aircraft, the research team found that landfill faces tend to be the largest source of methane emissions in U.S. landfills. Their findings are published in the journal Environment Science and Technology. The researchers are from Carbon Mapper, a California nonprofit that works to find ways to reduce greenhouse gas emissions, Arizona State University, and the U.S. Environmental Protection Agency.

The main gas that causes climate change is carbon dioxide. This is mainly due to the huge amount of gas being pumped into the atmosphere. Methane actually blocks heat better than carbon dioxide, but it doesn’t get much attention because it emits less overall. Still, environmentalists have grown concerned about the gas as more sources have been discovered in recent years.

In this new effort, the research team focused on methane emissions from landfills. Landfills tend to release methane from the decay of plant-based materials (usually discarded food waste). To learn more about the methane emitted by landfills, the researchers chartered a plane and used air quality measurement equipment to fly as low as possible over 217 landfills in 17 states. Measurable amounts of gas were detected in half of them.

The research team discovered a surprising source. Most of the emissions they detected came from the so-called working face, the part of the landfill where fresh waste is dumped. Very little comes out of other parts of the landfill.

The researchers also found that most landfills using gas capture technology still release measurable amounts of gas into the atmosphere. They suggest this is because these landfills are typically the largest and therefore emit the most methane. Despite capture efforts, significant amounts are released into the atmosphere. The researchers were also surprised by the number of landfills that emit no measurable amounts of methane.

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