Methane leakage thresholds for net climate benefits of wastewater biogas recovery

Biogas recovery is crucial for decarbonizing water resource recovery facilities (WRRFs), offering renewable energy production alongside waste treatment. However, methane (CH4) leakage during digestion and biogas handling can largely compromise their climate benefits, yet this risk remains uncharacterized. Here we present a US national-scale assessment of CH4 leakage thresholds beyond which WRRF biogas systems lose net climate benefits. By compiling measured leakage data from over 50 facilities and all available literature, we found the leakage rate ranged from 0.4% to 65%, and a large fraction of current systems exceeds the net-zero emission threshold, indicating substantial climate risk. The regional- and technology-specific scenario and sensitivity analyses show that net-zero thresholds range from 2% to 10% of biogas produced, depending on heat recovery, grid emissions intensity and biogas utilization pathways. Grid decarbonization further shifts these tolerances, making renewable natural gas systems more viable than combined heat and power in future low-carbon energy contexts. The analysis offers a quantitative roadmap showing how targeted leak detection and repair can transform most facilities from climate liabilities into assets, delivering both climate and economic gains and underscoring the urgent need for binding methane monitoring and mitigation policies to realize the net-zero potential of wastewater biogas. Biogas recovery enables renewable energy production alongside waste treatment, but the climate benefits are compromised by methane leakage. Here the authors systematically assessed how to manage methane leakage for sustaining net climate benefits of wastewater biogas recovery.