The importance of conductive materials characterization and synthesis conditions in understanding DIET through biomethane production: A review

Anaerobic digestion (AD) is a natural biological process by which organic materials can be broken down to produce biogas economically. The main components of biogas are CH₄, CO₂, and H₂S, with CH₄ being the most important. Several studies have discovered new materials to advance CH₄ production through the reduction of CO₂ and enhanced electron transfer through direct interspecies electron transfer (DIET). The current review will highlight the limited use of characterization techniques such as XPS, CHNS, and BET in the published biogas and biomethane articles in choosing suitable materials, either in biomass or biochar, based on their synthesis conditions, structure, pore size, and conductivity. Moreover, it will also include a discussion about the control of pyrdinic-N, pyrroldinic-N, and graphitic-N based on their conductivity and relation to DIET. The factors that may enhance DIET and increase methanogenesis in biochar or nanoparticles will also be discussed. The possible adverse effects of some nanoparticles and their relation to reactive oxygen species (ROS) formation, which may decrease biogas production, will also be discussed. Finally, the optimization strategy that should be adapted and employed in future biogas studies will be outlined.