Techno-economic analysis and life cycle analysis of renewable natural gas production from brewery wastewater via ex-situ methanation processes

As sustainability becomes increasingly critical, the brewing industry encounters challenges in managing high-organic-content wastewater, a promising renewable energy source. This study evaluates the economic feasibility and environmental impacts of converting brewery wastewater into renewable natural gas (RNG) through anaerobic digestion and biogas upgrading, with an emphasis on different hydrogen sources for biomethanation. Four scenarios were analyzed: Scenario 1 uses purchased hydrogen, while Scenarios 2-4 use renewable hydrogen from microbial electrolysis cells and water electrolyzers. Results show that capital investments for processing 139 MT/h of wastewater, yielding 208 m³/h of RNG, range from 10.6 M to 31.9 M USD, with estimated minimum selling prices of RNG between 2.25 and 4.37 USD/m³. Life cycle greenhouse gas (GHG) emissions span from -21 to 32 g CO₂-equivalent per MJ of RNG. This study presents key economic and environmental metrics for RNG production from brewery wastewater, offering insights to enhance sustainability in brewery wastewater management.