Cutting interval of Napier grass affecting methane yield in anaerobic digestion

Digestion of Napier grass at cutting intervals of 30, 45, 60 and 90 days was investigated in two-stage anaerobic reactors. Four sets of reactors with working volumes of 4 and 5 L for acidogenic and methanogenic reactors were operated at 30 degrees C. Acidogenic reactors were fed slurry of Napier grass at 200 ml/day. Hydraulic retention times were 20 and 25 days for the acidogenic and methanogenic reactors, respectively. Mixed ruminal microorganisms from cow were used as inoculum. The highest methane yield was obtained from Napier grass with a cutting interval of 60 days producing 6,500 m(3)/ha.year.