Environmental assessment of a two-stage high pressure anaerobic digestion process and biological upgrading as alternative processes for biomethane production

Abstract

Biomethane plays a key role in achieving decarbonization and sustainable development goals. According to the objectives that arise, choosing the most suitable production system allows optimization of production, thereby reducing CO₂ emissions. In this study, three biomethane production scenario life cycle assessments were compared to determine which would maintain the lowest CO₂ emissions. Conventional anaerobic digestion and an innovative process called two-stage high pressure anaerobic digestion were considered. These methods were combined with two upgrading processes: water scrubbing and biological upgrading. Cattle manure and sugar beets were used as substrates for the process. Emissions were 805.6 gCO₂eq/m³CH₄ for the traditional biogas production process combined with water scrubbing and 450.3 gCO₂eq/m³CH₄ for the two-stage anaerobic digestion process combined with biological upgrading. Furthermore, the analysis demonstrated that these values would be reduced by 29.5 % and 48.0 % if electrical energy were produced using only renewable energy sources.

Keywords: Biological upgrading; Biomethane; Life cycle assessment; Two-stage anaerobic digestion; Water scrubbing.