A crucial review on the challenges and recent gas membrane development for biogas upgrading.

Abstract

Biogas is a renewable energy produced from the anaerobic digestion process. It is mainly composed by 70% methane (CH4) and 30% carbon dioxide (CO2), with minor fraction of hydrogen sulphide (H2S) and other impurities. Anaerobic digestion is an important process to produce biomethane with above 90% CH4 after biogas upgrading. The CO2, H2S and other impurities are undesired, resulting in reducing the calorific value of biogas and if not removed creating various operational problems (i.e., corroding the pipelines and machines). Therefore, those impurities need to be removed by various upgrading technologies. Recently, membrane technology has gained significant interest in biogas upgrading, due to its simple fabrication, easy to handle, and its promising economic viability. Nevertheless, even though significant efforts have been devoted to enhance the membrane material properties, there are persistent challenges on the trade-off between permeability and selectivity on the membrane separation performances. In this review, recent developments of membrane technology tailored for biogas upgrading are thoroughly summarized. The fundamental aspects of material fabrication including the structure and classification are critically described. Furthermore, the effective approaches to overcome the permeability and selectivity trade-off as well as other challenges are comprehensively discussed. Finally, future research required to tackles the biogas upgrading issues is also projected.