Abstract
In this study, the effect of anaerobic co-digestion of grass hay and sewage sludge was investigated by experiments under the mesophilic condition on the process of methane generation from mowed cuttings generated during the maintenance of green tracts of land. The results were as follows. Co-digestion using an existing digestion facility was judged to be impossible because grass hay is light and stable, and so did not keep good condition on mixing and draining of the digesting sludge liquor. Instead of a complete mixing digester, the method of circulation and sprinkling of digesting liquor on the surface of piled-up grass hay was tested. The gas generation of grass hay by co-digestion was 390 L-gas/kg-TS and 200 L-CH4/kg-TS, and the digestion ratio was 60%.
