ABSTRACT
Bio-hythane has attracted increasing attention recently and emerged as a promising alternative to fossil-based fuels due to cleanliness, carbon dioxide (CO2) neutrality, high calorific value, and environment-friendly nature. It is a blend of hydrogen–methane, with typical mixture of 10%–15% hydrogen (H2), 30%–40% CO2, and 50%–55% methane (CH4). The hydrogen concentration in hydrogen–methane blend sometimes can reach up to 30% v/v. Bio-hythane is generally produced from a wide variety of feedstock materials by two-stage fermentation technique, i.e., dark fermentation followed by anaerobic digestion. However, the bio-hythane yield is regulated by several factors, such as co-digestion of substrates, pretreatment methods, biomass type, organic loading rate, pH, temperature, microbial consortium, and type of fermenter (single/dual stage) used. Firstly, this book chapter discussed the possibility of co-digestion to improve the bio-hythane yield in state-of-the-art manner. Secondly, the role of different pretreatment strategies adopted for feedstock for improving the bio-hythane yield are addressed independently and in combination. Generally, pretreatment method choice (mechanical/physical, chemical, thermal, and biological) depends on type of feedstock materials. Additionally, pretreatment methods are compared with regard to energy efficiency, yield, and environmental sustainability. Further, the major advancement of improving yield due to organic loading rate, biomass type, pH and temperature changes, microbial consortium, and fermenter type has been reviewed. Finally, the challenges and perspectives of bio-hythane production will be addressed. The outcomes of the present book chapter will provide valuable information to researchers and scientific community, and stakeholders for effective policy implementation.
