Methane generation during anaerobic fermentation of four livestock slurries

In order to promote livestock slurry recycling, the characteristics of methane generation from pig manure, cow dung, chicken dung and duck dropping during anaerobic fermentation were analyzed by using glass anaerobic fermentation equipment. On specific dates, the methane volume, pH and ammonia nitrogen content of fermentation liquid were measured within 20 days. The results show that after 20 days fermentation, total generated methane from cow dung, duck dropping, pig manure, chicken dung is respectively 2 649 mL, 2 515 mL, 1 964 mL and 1 278 mL. The volume of methane generated from per unit total solids is respectively 47.60 mL·g^-1, 45.23 mL·g^-1, 37.27 mL·g^-1 and 33.49 mL·g^-1. Pig manure prone to acidification during anaerobic fermentation, pH of fermentation liquid decreases to 5.62 at the first 10 days, thereby reducing methane generation. For the chicken manure under anaerobic condition, methane generation weakens with increasing ammonia nitrogen. It is therefore concluded that both pH and ammonia nitrogen soured by fermentation of raw materials are the key factors influencing methane generation of livestock slurries.