Integration of high-solid digestion and gasification to dispose horticultural waste and chicken manure

To realize full energy recovery from grass and chicken manure (CM), the integration of high-solid anaerobic digestion (HSAD) and gasification was investigated experimentally. The anaerobic biodegradability of grass can be enhanced through codigestion with CM. When the volatile solid (VS) ratio of CM to grass was 20:80, C/N ratio calculated to be 21.70, the cumulative biogas yield was the highest, 237 ml·(g VS)− 1. The enhancement of biogas production was attributed to the buffering effects of ammonia and rich trace elements in CM. In semi-continuous systems, when the organic loading rate was 4.0 g VS·L− 1·d−1, the HSAD process was stable, with the average biogas yield 168 ml·(g VS)− 1. More than 80% fractions of the digestates were volatile matters, which meant that the digestates can be used as feedstock for gasification to produce syngas. The VS ratio of grass to CM had significant overall energy generation through HSAD and gasification. Compared with gasification of digestate, cogasification with woodchips increased syngas yield and low heat value (LHV). Increasing of mass ratio of digestates to woodchips led to the decrease of LHV.