Methane and around 40% CO2 are produced by biogas facilities. While biogas may be used to create electricity and heat in combined heat and power plants, or it can be processed to natural gas grade and supplied into the natural gas network, the CO2 has escaped into the atmosphere unutilized.
Getting the most out of biogas Fraunhofer Institute for Microtechnology and Microsystems (IMM) researchers now wish to change that. “We transform CO2 into methane using green hydrogen,” explains Dr. Christian Bidart, a Fraunhofer IMM scientist, on the novel process’s technique. The generated biogas may be used to the full amount, not only to roughly 60% as before.
The fundamental response has been known for over a century, although it has mostly remained a laboratory experiment. Only conceivable applications will be the focus of the next energy shift, thus the researchers are putting the reaction into an industrial procedure for the first time.
50 kW demonstration system
In the ICOCAD I project, the research team has already created a demonstration system that transforms one cubic meter of biogas per hour into one cubic meter of methane and produces ten kilowatts of heat output. The researchers are presently expanding this system to five times its original scale, i.e. to a thermal output of 50 kilowatts, in the follow-up project ICOCAD II.
The extremely dynamic procedure is one of the difficulties on the table. Because the quantity of power created by wind and solar systems varies widely, so does the amount of green hydrogen produced by electrolyzing water with electricity. As a result, the system must be able to react swiftly to changing hydrogen levels. Hydrogen storage might also be conceivable, but it would be difficult and expensive. “As a result, we’re aiming to make the system more flexible so that we can avoid storing hydrogen as much as possible,” Bidart explains.
This involves, among other things, CO2 storage, because the quantity of CO2 emitted by biogas plants remains constant.
The creation of effective catalysts
The development of effective catalysts for the reaction was also a hurdle. Fraunhofer IMM researchers employed a precious metal micro-coating to achieve this. The principle: Hydrogen and carbon dioxide travel via a network of micro-channels that allow them to react with one another and have catalyst-coated walls. “By doing so, we may enhance the gas contact surface with the catalyst material while reducing the quantity of catalyst necessary,” Bidart explains. In the reaction reactor, many of these microstructures are piled on top of one another.
More scaling is in the works
The researchers are now working on the broader system’s implementation and dynamic functioning. The team wants to put this into operation and test it in a real biogas plant in 2023. However, this is far from the conclusion of the upscaling process; after all, the biogas plants create significant volumes of CO2. The researchers hope to increase the system’s capacity to 500 kilowatts by 2025, and by 2026, it should be able to generate one to two megawatts of power.
