Techno-economic-environmental assessment of the integration of power-to-X and biogas utilization towards the production of electricity, hydrogen, methane and methanol

Abstract

The valorisation of biogas is a key element of the circular economy. This study provides an integrated techno-economic-environmental analysis of the most common technologies for the integration of biogas valorisation in the energy system. This involves both the use of biogas in the production of electricity and chemicals and the use of biogenic CO₂ as a source for power-to-X. In this latter case, biogas can be seen as a platform for electricity or H₂ storage. The study helps in understanding the most suitable product for biogas valorisation, according to the boundary conditions set by the energy sector. Two different cases were considered: when electricity, methane or methanol are directly produced from biogas and when biogas is used to seasonally store renewable electricity, taking advantage of the oscillations in the electricity price. It was found that methanol is the most profitable product from biogas, thanks to the high value of this chemical. Methanol synthesis is profitable for a biogas price up to 0.09 € per kW h, while methane production shows a positive income up to a biogas price of 0.08 € per kW h. When considering the use of biogas in energy storage, it was found that methane is the best carrier for electricity storage, while methanol is the best storage medium for H₂. The average electricity production price is 0.18 € per kW h using methane as the storage molecule, while this value is in the order of 0.20 € per kW h for methanol. When looking at H₂ production price, it was observed that the route via methane originates costs of 0.15 € per kW h, but the methanol route is less expensive at 0.14 € per kW h. This study shows that the selection of the most suitable pathway for valorisation of biogas should carefully account for the boundary conditions of the energy system, considering the needs of the final users. The flexible combination of upgrading and power-to-X opens the way for broader potential of biogas use.