Evaluation of biogas upgrading technologies and future perspectives: a review.

Biogas is acknowledged as one of the foremost bioenergy to address the current environmental and energy challenges being faced by the world. Commonly, biogas is used for applications like cooking, lighting, heat and power production. To widen the scope of biogas application, like transportation, natural gas grid injection and substrate for the production of chemicals and fuel cells, mainly CO2, H2S and other impurities need to be removed by various upgrading technologies. It is an important process to produce biomethane with above 90% methane. There are various physico-chemical (adsorption, absorption, cryogenic and membrane separations) and biological (in situ and ex situ) processes for biogas upgradation, and each process is site and case specific. The aim of the present paper is to thoroughly evaluate the existing and emerging biogas upgrading technologies. Analysis of each technology with respect to basis of operations, energy requirement, methane purity and recovery and cost economics has been carried out. A thorough analysis has been done on the major hurdles and the research gaps in this sector. For a wider and successful implementation of the biogas upgradation technology, the trends in research and development (R&D) such as development of efficient biogas upgrading technologies, adsorbents, reduction in cost and methane loss have been thoroughly evaluated.