The quality of biogas is significantly influenced by the composition of the feedstock used in anaerobic digestion and the control of pH during the fermentation process. Feedstock composition plays a crucial role because it determines the availability of biodegradable organic matter, nutrients, and microbial activity required for efficient biogas production. Different types of biomass such as agricultural residues, animal manure, food waste, and energy crops vary in their carbon, nitrogen, lignin, cellulose, and moisture content, which directly affects methane yield and gas purity. The carbon-to-nitrogen (C/N) ratio is one of the most important parameters influencing biogas quality. An optimal C/N ratio is necessary for maintaining microbial metabolism during anaerobic digestion. If the feedstock contains excessive carbon, microbial growth may become limited due to nitrogen deficiency, leading to slower decomposition and lower methane production. Conversely, a high nitrogen content may result in ammonia accumulation, which can inhibit methanogenic bacteria and reduce biogas quality by lowering methane concentration and increasing the proportion of carbon dioxide and other impurities. Lignin content in feedstock also affects biogas production