Evaluating economic opportunities and challenges for energy recovery from methane leaks during wastewater treatment

Sahar Head El Abbadi, Trung Le, Abigayle Rose Hodson, Evan David Sherwin , Joaquin Jamieson, Cuihong Song, Zhiyong Jason Ren, Jennifer R. Stokes-Draut

Methane leaks from wastewater treatment represent the loss of biogas that can be used to generate onsite energy, offsetting costs and improving efficiency. Here, we characterize emissions from water resource recovery facilities by compiling measurement data and calculating biogas-production normalized leak rates for facilities with anaerobic digestion. For plants where biogas data were unavailable, we developed an empirical method to estimate production using annual data from 43 facilities. However, we find notable differences in production-normalized leak rates from measurement data where biogas data was available (mean: 12% [95% CI: 8-17%], median: 8%) and those where production was empirically derived (mean: 34% [95% CI: 28-41%], median: 23%). Considering different techno-economic scenarios for leak rates and gas capturability, we find the largest 5% of facilities in the United States could recover over $100,000/year/facility in currently forgone revenue by capturing gas by capturing gas leaked at rates as low as 3%; at rates ≥25%, accrued value could reach several million dollars. We conducted a Monte Carlo simulation to determine the financial cost of methane leaks considering existing energy recovery facilities in the United States, with different scenarios for the underlying leak distribution, and find median annual loss could range from $13 million to $42 million nationwide.