What is biogas and how is it produced?

Biogas is a renewable fuel composed primarily of methane (50-75%) and carbon dioxide (25-50%), with trace amounts of hydrogen sulfide, ammonia, and water vapor. It is produced through anaerobic digestion - the microbial breakdown of organic matter in the absence of oxygen. The process involves four stages: hydrolysis (complex organics broken into simpler molecules), acidogenesis (sugars and amino acids converted to volatile fatty acids), acetogenesis (VFAs converted to acetate, hydrogen, and CO2), and methanogenesis (methanogens produce methane from acetate or H2/CO2). Feedstocks include agricultural waste, animal manure, food waste, sewage sludge, and energy crops. Biogas can be used directly for heat/power generation or upgraded to biomethane for grid injection or vehicle fuel.