METHANE FERMENTATION PROCESS

PURPOSE:To increase the amount of the raw material and to improve the efficiency of methane fermentation, by discharging the residual liquid of methane fermentation to the water area for the cultivation of water grasses and algae, thereby making the area eutrophic. CONSTITUTION:A plurality of nearly vertical cylinders 3 having open top and bottom ends are arranged in the water area 2 for the cultivation of water grasses and algae to be used as the raw material of methane fermentation. The top end and the bottom end of the cylinder are positioned near the water surface and the bottom, respectively. The residual solid and liquid of methane fermentation are discharged through the pipe 4 to the lower part of the cylinder, and at the same time, CO2-containing gas is introduced through a gas diffuser 6 to the lower part. The bottom sludge rich in nutrients is diffused from the bottom 7 of the water to the whole water area by the bottom flow 9 caused by the upward flow in the cylinder.