DUEME

The X-Energy sub-project DUEME (direct conversion of electricity into methane) is researching possible methods for sustainable electricity storage. The focus is on a new and promising power-to-gas (PtG) technology known as electromethanogenesis. In this process, excess electricity is used to convert carbon dioxide into methane with the help of microorganisms. The energy can then be stored in a chemical compound and can replace fossil natural gas, which consists primarily of methane. The methane is then fed into the existing natural gas grid without any problems and used as a green energy source.

Electromethanogenesis is an alternative PtG process in which the previously separate process steps of "electrolysis" and "methanation" are combined. The CO₂ is converted directly into methane using electrons without intermediate electrolysis. Renewably generated electricity is used for this. In contrast to conventional biological methanation, in which hydrogen is fed into a bioreactor, significantly better efficiency can be expected as the process is not limited by the poor solubility of hydrogen in water.

The DUEME project comprises five areas of work:

• The first involves the planning and procurement of instruments for the investigation of electromethanogenesis.
• The second involves isolating and cultivating various archaea and carrying out a molecular biological and biochemical analysis of these cultures or various reference cultures in the so-called H cells.
• In the third and fourth, unknown metabolic pathways are investigated.
• The fifth deals with the demonstration of electromethanogenesis.

Results

1. In the DUEME project, four different highly enriched methanogenic cultures have so far been isolated from various environmental samples with the aid of electromethanogenesis. These cultures were then analyzed for their purity and electrochemical properties. An H-shaped cell, which was further developed in the project, was used to ensure the closer investigation of bioelectrochemical reactions.
2. In addition to the further developed H-cells, a semi-automated H-reactor will then be constructed for a more detailed investigation of electromethanogenesis. Various physical variables will be considered in order to develop a targeted control of electromethanogenesis.

The results from the DUEME sub-project will be used and continued in the sub-project EmSpe.