Transforming biogas into biomethane using membrane technology

Upgrading biogas, i.e., the removal of CO2 from CH4 is an attractive regenerative energy as it is supplied continuously. Conventional upgrading techniques such as absorption or adsorption require significant amounts of energy and require equipment of large size. Hence, we give an overview on gas permeation membrane processes which are applied in biogas upgrading. Here, we consider the upgrading process as a whole. The multiscale design of membrane-based gas separation is analyzed in detail. Membrane materials, gas permeation modules and their respective operation as well as gas permeation processes for biogas upgrading are investigated. Applying gas permeation modules, compression of the feed gas should be used since it is energy efficient for gases with high amounts of CO2. Single stage gas permeation processes are not able to produce a high CH4 purity and simultaneously obtain a high CH4 recovery. Hence, multistage concepts are mandatory. Membrane-based upgrading systems are an interesting alternative to conventional biogas upgrading equipment and we expect that they will significantly contribute to the energy supply of the future.