Potential of methane production by thermophilic anaerobic co-digestion of pulp and paper sludge with pig manure.

This study investigated the potential of methane production of thermophilic anaerobic co-digestion of diluted pulp and paper sludge (DPPS) with diluted pig manure (DPM). The mixture ratios, that is, pulp and paper sludge (PPS) and pig manure (PM) were mixed with tap water to create slurry with a volatile solid (VS) content of 4% as substrate, respectively. The co-digestion was carried out in a 2 liter reactor tank which was stirred semi-continuously with a five phase organic loading rate (OLR) consequently the contents were being drawn-and-fed daily. This experimental design was operated by a triplicate with steady state operations during a thermophilic condition of 50 degrees C and a constant solid retention time (SRI) of 10 days. The results demonstrated that the co-digestion of DPPS and DPM mixture ratio (50:50) resulted in higher methane production, specific methane yields (SMY), and soluble chemical oxygen demand (SCOD) removal efficiency. The highest methane content of biogas, SMY, volatile solid (VS) degradation rate and SCOD removal efficiency of 56.54 +/- 4.21%, 71.58 +/- 8.75 ml-CH4/g-VSadded, 55.74 +/- 0.27% and 83.54 +/- 6.32%, respectively, were achieved with process stability. However, it added too high mixture ratio of PM to reduce methane yield and SCOD removal efficiency. This study showed that there was a good potential of PPS and PM on thermophilic anaerobic co-digestion for methane production.