Emerging technologies for biogas production: A critical review on recent progress, challenges and future perspectives

Biogas is a resource of renewable energy with the highest significance to development in many countries due to the great accessibility to biomass. It is mostly produced by the anaerobic digestion of various feedstocks, but technologies such as landfilling, aerobic composting and incineration are also being used. The current novel review aimed to present emerging technologies for biogas pretreatment, production and upgrading process. Furthermore, various applications together with a current and future perspectives of biogas have been covered. It was found that pretreatment technologies such as chemical, physical, thermochemical and oxidative are increasing biomethane and biogas yield. Hence, extrusion pretreatment has increased biomethane production by 190 %. The novel technologies for biogas upgrading, such as photosynthetic biofixation of CO2 by microalgae have shown that upgraded CH4 have maximum CO2 content in the biogas ranging from 2 to 6 %. Microbial electrolysis cell technology is sustainable and effective for biogas upgrading with a low requirement of energy. Thus, it was found that bioelectromethanogenesis leads to the uptake of 13.2 gCO2/d. In addition, nanobubble technology is in recent studies extensively investigated for the improvement of methane yield. In Europe around 70 % of biogas plants are utilising the feedstocks from agriculture sectors. In 2022 global combined production of biogas and biomethane has reached more than 1.6 EJ which is an increase of 17 % in the last five years. Fossil fuels are the primary global energy source with around 85 % of the world's energy supply. Hence, wider use of biogas could ensure the goals for the implementation of sustainable renewable energy.