A controlled release experiment for investigating methane measurement performance at landfills

We assessed the performance of various methane measurement solutions in landfill applications during November 6, 2023 and November 14, 2023. A measurement solution is defined as a system or market offering that quantifies and/or localizes emissions. Our study involved full-scale multipoint- and area-source (dispersed) controlled releases of methane from the ground surface of a closed 25-ha landfill with collection system and a background emission rate of 24 kg/h. Most quantification methods performed well, but the truck-based Tracer Correlation method performed the best with an uncertainty of ±20%. Drone flux plane methods also performed well with an uncertainty of ±34% with very few outliers in the best-case scenario. For leak detection, aerial LiDAR demonstrated a 100% detection probability down to the lowest emission rates, whereas drone column sensors emulating EPA 21 surface emissions monitoring (SEM) were 100× less sensitive. Continuous sensors, trucks, and other methods were also assessed. Results indicate that many of the current quantification methods are effective, and potentially more accurate than first-order decay models, though they still need to be applied in a replicated fashion for robust site-level estimates. Detection outcomes were variable, and questions remain, such as how the evaluated methods would compare the against regulatory SEM method, the impact of spacing and trigger thresholds (which differ regionally in regulation), and what detection level is actually necessary for effective landfill gas management. This site provides a future test bed for answering these other questions.