Abstract:In order to improve the volumetric gas production efficiency of pig manure in continuous biogas engineering and reduce its heat loss during the feeding and discharging process, this study plans to use high concentration and small volume feeding methods. Fresh pig manure will be diluted into three levels of total solid mass fraction (TS) of 10%, 12%, and 14%, respectively. The load of each reactor will be changed by gradually shortening the hydraulic retention time (HRT) (HRT: 25 d → 20 d → 18.5 d). The experimental results showed that when HRT was 25 days, the average daily gas production of each group was relatively high, about 460 mL/g, and a biogas conversion efficiency of over 85% could be obtained at this stage; When HRT: 20d, all groups achieved a high volumetric gas production rate of 2.29 L/(L · d) (TS: 14%); When HRT decreased to 18.5 days, the gas production of all groups showed a decreasing trend, indicating that the organic load had exceeded the reactor's maximum conversion capacity. By integrating the conversion efficiency of raw material gas production and volumetric gas production efficiency, it was found that the optimal combination conditions were a feed TS of 14% and HRT of 25 days. This study can provide reference for how to coordinate the relationship between feed concentration and HRT in practical biogas engineering.