FlaeXMethan describes a process with which biomethane can be produced in a flexible manner from biogas and hydrogen from surplus electricity in a combination of biological methanation and membrane-based gas treatment.

In the present project it shall be investigated whether a biological methanation unit based on the ex-situ principle can be combined with a downstream membrane-based biogas upgrading including control. The aim is to biologically produce methane from renewable, surplus CO₂ and renewable H₂ in order to improve the efficiency of biogas plants. This will be done by a novel approach to CH₄ production from CO₂ and hydrogen using a customized microbiome. By means of a new gas upgrading system, it will be possible to produce biogas-based biomethane with a usability that is in no way inferior to fossil gas.

This project will contribute to innovative technical-scientific developments in the field of ex-situ methanation as well as gas upgrading and integration into the overall system, to initiate a significant technology push for regenerative CH₄ production from gaseous biological sources. This novel process allows a complete flexibilization of the power-to-gas process for the production of renewable methane from renewable excess electricity. Thus, the output of biomethane can be increased by up to 80% compared to a conventional biogas plant without methanation.

The main objective of the project is to establish an economically viable process for the production of biomethane in biogas plants, which is currently little and medium-term largely independent of public subsidies. To this end, existing biogas plants are to be expanded to include two key components, firstly a biogas upgrading unit and secondly a methanation unit.

In order to meet the guidelines for feeding biomethane into the natural gas grid, the gas mixture obtained from methanation must be upgraded what is done via a multi-stage membrane separation process. It should be able to automatically handle different material streams and compositions in such a way that biomethane of the same quality is produced constantly. Thus, regenerative excess electrical energy can be chemically stored with low losses and is made available as a chemical building block to the entire range of applications in industry.

In the plant network consisting of biogas plant, methanation and upgrading, the proposed concept creates an electricity storage unit which provides a renewable raw material that can be used 100% in a closed material cycle. In addition to its function as a long-term storage of electrical energy, biomethane can also be provided to chemical industry in the future as a renewable carbon supplier.