Performance Evaluation of a Large-Scale Swine Manure Mesophilic Biogas Plant in China

Abstract

Abstract. With the rapid growth of large-scale and intensive swine farms have come many ecological and environmental problems associated with the substantially increased and concentrated animal waste production. In this article, a swine manure and flushed slurry to renewable energy management system is present and discussed. This system was installed in a commercial feeder-to-finish swine farm with 18,000 head of swine in Beijing, China, and included two mesophilic upflow solids reactors (USRI and USRII, 500 m3 and 700 m3) and one psychrophilic plug-flow reactor (PFR, 1000 m3). In this study, USRII was monitored throughout a whole year to evaluate the performance of this swine waste to energy system. The biogas plant used mixed solid swine manure and flushed slurry as substrate with a relatively low organic loading rate (OLR) of 0.7 to 1.8 kg volatile solids (VS) m-3 d-1. The hydraulic retention time (HRT) varied from 15 to 22 days depending on the season. Less added water contributed to the longer HRT and more concentrated influent in winter. In winter, the specific methane production (SMP) of the digester was 0.43 m3 CH4 kg-1 VSadded, which was slightly lower than the value reported in Europe (0.45 m3 CH4 kg-1 VSadded) but about 48.3% higher than that in Asia (0.29 m3 CH4 kg-1 VSadded). This indicated that the performance of this USR in winter was stable, with a higher biogas production, and up to 90% of the VS was removed as well. However, the low OLR limited the volumetric methane production rate to only 0.21 to 0.57 m3 m-3 d-1. Keywords: Flushed slurry, Large-scale biogas plant, Monitoring, Performance, Swine manure.