Spatially resolved national assessment of renewable natural gas potential from water resource recovery facilities through biomethanation

Renewable natural gas is a promising energy source that can seamlessly leverage existing energy infrastructure. For water resource recovery facilities with onsite anaerobic digestions, a promising pathway exists to upgrade the raw biogas to renewable natural gas through biomethanation. This study provides the first spatially resolved national assessment that formulates a global optimization problem to understand the economic impact of biomethanation and major impacting factors, assuming the existing presence of electrolysis and combined heat and power infrastructure. We found that large facilities have promising biomethanation opportunities, but the fundamental economic viability of these projects is overwhelmingly dictated by policy-driven premiums, specifically federal Renewable Identification Number (RIN) credits, and the evolving H₂ market. The treatment capacity, distance to natural gas pipelines, and the market prices of RIN and H₂ are the major impacting factors and should be carefully evaluated for individual facility decisions. State policies such as Low Carbon Fuel Standard provide meaningful incentives to boost biomethanation adoption but federal incentives are still vital to RNG project feasibility.