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

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 CO emissions. In this study, three biomethane production scenario life cycle assessments were compared to determine which would maintain the lowest CO 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 gCOeq/mCH for the traditional biogas production process combined with water scrubbing and 450.3 gCOeq/mCH 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.