Techno-economic assessment of atmospheric carbon removal via anaerobic digestion of biomass waste

Abstract

Anaerobic digestion (AD) is a mature technology for converting organic waste into renewable methane, with growing interest in capturing the co-produced biogenic carbon dioxide (CO 2 ) for atmospheric carbon removal. This study addresses key knowledge gaps by designing and evaluating greenfield, industrial-scale AD facilities integrated with CO 2 capture across four representative feedstock categories: wastewater, food waste, industrial ethanol waste, and agricultural/animal waste. Each waste stream was extensively characterized for total solids (TS), volatile solids (VS), and biochemical methane potential (BMP), with results informing life cycle assessments (LCAs) and techno-economic analyses (TEAs). Among the feedstocks, food waste achieved the lowest carbon capture cost at $755/tonne CO 2 captured, followed by agricultural/animal waste ($785), industrial ethanol waste ($808), and wastewater ($3,791). Agricultural/animal waste exhibited the highest BMP (544 mL-CH 4 /g-VS), while wastewater yielded the lowest (341 mL-CH 4 /g-VS), but had the highest methane content in biogas (79%). When accounting for life-cycle emissions, carbon removal costs were lowest for agricultural/animal waste at $789/tonne CO 2 , compared to $1,325 for food waste and $2,182 for industrial ethanol waste. Sensitivity analyses identified feedstock capacity, discount rate, methane selling price, CO 2 concentration, and biomass transport distance as major cost drivers. Through the design and analysis of feedstock-specific AD systems with integrated CO 2 capture, this work provides one of the first comprehensive evaluations of carbon removal via AD. While removal costs remain higher than some alternatives, scaling and technology optimization could enhance the role of AD in integrated waste valorization and carbon management systems.