Nanomaterials in Sustainable Biogas Production

Biogas production through anaerobic digestion (AD) represents a cornerstone of sustainable energy technologies, yet conventional systems often suffer from limited efficiency, process instability, and inadequate gas quality. Nanomaterials (NMs) have emerged as promising additives to enhance biogas production in AD, offering high surface area, conductivity, and reactivity to stimulate microbial conversion. Carbon-based (e.g., CNTs and graphene), metal and metal-oxide (e.g., Fe, Ni, TiO₂), semiconductor, and hybrid nanocomposites have been studied for this purpose. Owing to their high surface area, catalytic activity, and redox-mediating capacity, NMs can accelerate hydrolysis, enhance electron transfer between syntrophic consortia, and mitigate inhibitory intermediates (e.g. H 2 H 2 S, phenolics), improving process stability and gas composition. The overall effect is often a significant increase in CH 4 yield and productivity. These materials facilitate microbial growth and syntrophic consortia via nutrient adsorption and redox-active surfaces, notably promoting direct interspecies electron transfer (DIET) and catalytic hydrolysis of complex organics. However, challenges remain: excessive nanoparticle doses can inhibit microbes through toxicity and cost of engineered NMs raises environmental and economic concerns. Beyond laboratory demonstrations, emerging applications highlight the potential for nano-bio hybrid systems, integration with microbial electrolysis cells (MEMs), and circular economy models (CEMs). Critical considerations of nanoparticle dosage, recovery, and environmental safety are addressed to ensure sustainable deployment. By uniting mechanistic insights with applied perspectives, this chapter positions NMs not merely as additives but as enabling tools for next-generation biogas technologies, with significant implications for renewable energy, waste valorization, and climate change mitigation.