Gaseous Biofuels in Biorefineries: Biomethane

The global production of biomethane is rapidly emerging as a sustainable alternative to fossil fuels for energy generation. Biogas, where methane (CH₄) is usually one of the main components, is generated through the anaerobic digestion (AD) of various organic substrates, including animal manure, organic wastes, and wastewater. The efficiency of the AD process depends on key operational parameters and reactor designs that optimize microbial activity and gas yield. However, inhibitory compounds such as heavy metals, ammonia, and volatile fatty acids (VFAs) can significantly impact microbial metabolism and biogas production. To enhance substrate availability for microbial degradation, different pretreatment methods are often employed, as well as current advances in the AD focused on DIET enhancement and co-digestion technologies. This chapter provides a comprehensive overview of common substrates for AD, the impact of operational parameters, and strategies to mitigate the effects of inhibitory compounds. It also examines the latest advancements in reactor designs for effective monitoring and control of the digestion process. Additionally, the chapter explores biogas production for electrical energy generation, along with the purification technologies required to upgrade biogas to biomethane. Finally, it discusses the applications and value-added products derived from biomethane and its integration into circular economy frameworks. It involves the advantages and gaps hindering the full implementation of AD-derived energy worldwide.