Biomass Sources for Biogas Generation: Feedstock Types, Biogas Yields and Sustainability Aspects

Biogas production through anaerobic digestion is an established strategy for converting organic residues into renewable energy and nutrient-rich digestate. This review compares the suitability of agricultural, animal, municipal, household, industrial, and aquatic biomass for biogas production, with emphasis on feedstock composition, process stability, methane yield, and co-digestion. Biogas typically contains 40–80% methane, while its energy potential depends strongly on substrate properties, including dry matter, volatile solids, carbon-to-nitrogen ratio, lignocellulosic content, and concentrations of potential inhibitors. Reported methane yields range from approximately 0.20 m3 CH4/kg volatile solids (VS) for cattle manure and 0.30 m3 CH4/kg VS for pig and poultry manure to about 0.50–0.60 m3 CH4/kg VS for food waste and up to 0.80 m3 CH4/kg VS for selected lipid-rich industrial residues. Among selected agricultural residues, rice straw produced 31.50 mL g−1 volatile matter, compared with 22.32 mL g−1 for maize cobs and 8.08 mL g−1 for sugarcane bagasse. Co-digestion frequently improved both process stability and yield; for example, mixing water hyacinth with 30% ruminal slaughterhouse waste increased biogas yield by 75%, from 8.05 to 14.09 L kg−1 biomass, and increased methane content from 59% to 68%. The review shows that feedstock selection should be based not only on methane potential but also on availability, transport distance, substrate purity, pretreatment needs, nutrient balance, digestate management, and local energy demand. Waste- and residue-based co-digestion systems are particularly promising because they combine renewable-energy generation with improved waste management and nutrient recycling.