The effects of temperature on biogas production rate and purity

<br />This study investigated the effects oftemperature onthe performance ofanaerobic digesters for biogas production. Digesters were filled with a1 : 1 ratio ofsubstrate towater, containing 15kg ofcow dung and 3kg ofcrop waste, and maintained attemperatures of50±2C and 30±2C, corresponding tothe thermophilic and mesophilic biodigesters, respectively. The experiments run for 75days, and biogas production rate and purity were measured. The thermophilic digester produced 48.4% more biogas and had aslightly higher pH (7.65) than did the mesophilic digester (7.37) bythe end ofthe observation period. However, gas chromatography revealed that the CH₄ and CO₂ contents did not significantly differ between the two treatments. The CH₄ concentration inthe mesophilic environment was 42±10%, whereas that inthe thermophilic environment was 53.5±10%. The CO₂ composition was 32.5±1% and 35.5±1% for the mesophilic and thermophilic setups, respectively. These were supported bythe wavelength (460nm to620nm) of the flame colour, indicating that the biogas from both setups is predominantly composed of methane. In conclusion, thermophilic anaerobic digesters may have a relatively high biogas production rate, but the biogas purity is not significantly different from that of mesophilic digesters.