Landfill methane capture runs at ~50% efficiency, not the 75% EPA assumes

Landfill operators and regulators rely on EPA models that assume gas collection systems capture roughly 75% of methane generated by decomposing waste. A 2024 study published in Science found the actual capture efficiency across U.S. landfills is closer to 50%, meaning nearly half of all landfill methane escapes into the atmosphere uncontrolled. This matters because methane is 80 times more potent than CO2 over a 20-year horizon, and landfills are the third-largest source of U.S. methane emissions. The gap between modeled and actual capture means every climate policy built on EPA inventory numbers systematically underestimates landfill contributions, leading to misallocated mitigation spending. Ironically, landfills with renewable natural gas (RNG) facilities -- the sites supposed to be best at capturing gas -- accounted for 79% of observed emissions in aerial surveys, because the construction disturbance from installing RNG infrastructure creates new fugitive emission pathways. The problem persists because there is no federal requirement for continuous methane monitoring at landfill boundaries; compliance is based on periodic surface emission monitoring and modeling assumptions, not real atmospheric measurements.