Combined supply of electricity and fuel at biogas plants ‒ economic efficiency of connection scenarios

Abstract

Due to the expiry of the original Renewable Energy Sources Act (EEG) remuneration for many biogas plants in the near future, as well as the severe cuts in the promotion of biogas power generation in the amended EEG 2017, the German biogas industry is faced with the question of which future connection concepts could be both economically attractive and promising in the long term. Fuel production from biogas would be one of the possible future options. Several studies forecast a shift in biogas utilization from electricity generation to fuel utilization by 2050. Politicians are also aiming for a higher implementation of bioenergy in the fuel sector. The focus of this paper is the economic evaluation of several connection scenarios with electricity and fuel production for existing biogas plants. In particular, a new flexibility approach with proportional electricity and fuel production with shares of 50% each in biogas utilization is to be investigated. With the help of flexible power generation schedules, local fuel demand data from vehicle fleets and the resulting fuel production schedule, the necessary additional biogas and high-pressure storage capacity and the necessary plant capacity for fuel production was determined. Subsequently, the economic evaluation was carried out according to the net present value method in order to be able to economically evaluate several connection scenarios for a representative model biogas plant. The comparison of the connection scenarios showed that the connection scenarios with fuel production are more economical than those with electricity production alone. Depending on how the planned national implementation of the new version of the European Renewable Energy Directive (RED II) is realized, the plant's economic efficiency – especially when increasing the proportion of liquid manure in the substrate composition – can improve significantly.