Comparison of biogas production efficiency of anaerobic digestion using water hyacinth and its juice from solid-liquid separation as feedstock

To exploit efficient technology of anaerobic digestion with water hyacinth, a laboratory experiment was carried out to assess the performance of water hyacinth and its juice from solid-liquid separation as feedstock in two continuous stirred-tank reactors (CSTR) at 35℃. Results showed that when using water hyacinth as feedstock for anaerobic digestion, the suitable organic loading rate (OLR) were 2.0 kg/(m3·d) with 27 d hydraulic retention time (HRT), and the relevant biogas production rate of volatile solid and the volume biogas yield were achieved at 267 mL/g and 0.61 m3/(m3·d) with 58% average methane content, respectively. Comparatively, using the juice of water hyacinth as feedstock for anaerobic digestion, the biogas production rate of chemical oxygen demand (COD) and OLR were 6 kg/(m3·d) and 1.4 m3/(m3·d), respectively, in which average methane content was 66%. Meanwhile, its HRT was reduced to 2.4 d. The reduction of COD and mixed liquor volatile suspended solids (MLVSS) were over 85% and 88%, respectively. Therefore, the juice of water hyacinth as feedstock for anaerobic digestion had higher utilization efficiency compared with water hyacinth itself, and consequently a new method for utilization of water hyacinth with less investment could be exploited.