Purification of biogas for methane enrichment using biomass-based adsorbents: A review

Among the others, CO₂ and H₂S are the major impurities present in biogas which typically hampers its direct application as biofuel. Therefore, an upgradation for the purity of biogas is a high research endeavour. In the recent past, several attempts are made to improve the quality of biogas with a focus to reduce the impact of global warming due to the excessive release of CO₂. This is interesting to indicate that most of the biogas cleaning methods are expensive and very rare documents detailed the usage of sustainable materials for the purification of biogas. Given that, developments in the applications of natural materials as low-cost adsorbents used for the purification of biogas are well documented in the present review paper. Globally more than 40% of the countries utilise water scrubbing as the most popular method for the separation of biomethane. This article also reviews the other most accepted technologies such as different types of scrubbing, swing adsorption, and cryogenic separation with biological upgradation. Hybrid biological methods are used in methane upgrading systems to increase production of pure CH₄ while reducing the need for energy and chemicals. Moreover, the article also summarized different numerical models, frequently adopted for the prediction of the upgradation of biomass. Finally, the article concludes with major bottlenecks involved in the processes and recommended scientific directives towards successfully transforming bench-scale studies into large-scale implementation. So, this article will ensure the readers gather overall technical information on the upgradation of biogas obtained from the anaerobic digestion of biomass.