A Pilot Study on Mesophilic Dry Anaerobic Digestion of Rice Straw

Dry anaerobic digestion technology with leachate circulated for untreated strawconversion to biogas was investigated in bioreactors at 35 ℃. Biogas production, pH, COD and methane content were tested. After 180 days ofanaerobic digestion, it was observed that the Reac- tor 2 with TS 20%( R2) had the largest biogas production( 2 048 Lin total) while the biogas production were 1 199.9 L, 905.9 Land 51.7 L, respectively, in Reactor 1, Reactor 3 and Reactor 4. The hemicelluloses of the digested strawin R2 decreased from 28.23% to 18.33%, and the pH value in zymotic fluid was stable at 7.0￣7.5. The reactor R3 with TS 30%( R3) went on a long period of acidification before its biogas production turned higher, while its methane content was higher than that from R2. Leachate recirculation reduced the waste stabilization and was effective in enhancing methane gas production and improving leachate. The result indicated that sluge could be the inoculum source for anaerobic mesophilic digestion of the treatment of rice strawat dry condition. This study provided useful parameters for the design of largescale dry anaerobic digester for straw conversion tobiogas.