Membrane-based technology for methane separation from biogas

In this chapter a historical and technical background for membrane gas separation is given, together with a review of the basic terms commonly used in the study of membrane separation technology. The mechanism of mass transport through the membrane, how this depends on the chosen membrane material, and how this affects the separation of gas molecules in biogas upgrading is described in detail. The present industrial membrane material of choice for biogas upgrading is polyimide, while carbon molecular sieves and mixed-matrix membranes combining polymers with either zeolites, graphene oxide, or metal-organic frameworks are promising emerging membrane materials. Biogas upgrading requires multistage membrane systems, preferably combined with cryogenic distillation to obtain grid gas and high-purity CO2. The economic evaluation indicates that production of grid-quality gas and CO2 from biogas could be economically attractive.