Anaerobic digestion of solid animal waste in an accumulation system at mesophilic and thermophilic conditions, start up

The anaerobic digestion of solid animal wastes has been studied in an accumulation system (AC) at a filling time of 60 days followed by about 50 days batch digestion at 40 and 50degreesC. Poor mixing conditions during anaerobic digestion of solid wastes promote stratification of the substrate and intermediate products along the reactor height. The effect of layers stratification has also been followed in the AC system. The results showed a pronounced stratification of both CODdis and VFA concentrations along the AC system height. The temperature had a minor effect on the methane yield. The results also showed that methanogenesis was rate limiting in the AC system while the hydrolysis was the rate-limiting step during batch digestion.