Development of an innovative two-stage fermentation process for high-calorific biogas at elevated pressure

The two-stage high-pressure fermentation (HPF) process enables the production of methane at high operating pressure. Pressure significantly reduces the energy needed for injecting the produced biogas into the gas grid by 45–60%. It also allows for incorporating large parts of the necessary biogas upgrading process into the synthesis step. As a result, the two-stage HPF process provides pressurized biogas with methane volume fraction ranging from 0.75 to 0.94. The pressure is not generated by energy intensive gas compression, but in-situ by microbial gas production. In comparison to conventional biomethane production, the overall costs could be reduced up to 20%. HPF is most beneficial when its operating pressure is adapted to that of the gas grid.