Biohythane as a sustainable fuel – A review on prospective synthesis based on feedstock preprocessing, optimization approach and circular economy concept

Hydrogen and methane are regarded as promising alternative and renewable energy sources with extensive potential owing to eco-friendliness during production and consumption. These fuels provide promising scope but are reported to have limited capabilities when their production is simultaneous. The possibilities in sustainable production of biohythane is also gaining more interest as it exhibits lesser impact on environment upon resourceful production. The biohythane yield depends on various synthesis factors and feedstocks available. The present article focusses on an elaborative review on the pretreatment strategies and techniques adapted for the feedstocks like food waste, municipal waste, wastewater treatment sludge, algal biomass, agricultural waste and other organic waste based on the reports of researchers. The methodologies adopted that unveiled greater improvement in the yield, synthesis techniques, optimization studies based on advanced tools and kinetic modelling in the synthesis method of biohythane involving the examination of reaction mechanism based on conventional models like the Anaerobic Digestion Model, Modified Gompertz model, Cone model and first-order kinetic model are also presented. An anaerobic digester with swine manure and pineapple waste feedstock was able to yield 1240 mL/L-d of hydrogen and 812 mL/L-d under optimum operating conditions. Special focus is given on the review of feedstock preprocessing techniques reported in recent researches that have yielded enhanced production yield of the target fuel. The article also focusses on circular economy, impact of this renewable fuel on environment and life cycle analysis of biohythane.