Comparison of anaerobic co-digestion of pig manure and sludge at different mixing ratios at thermophilic and mesophilic temperatures.

[Display omitted] • Co-digestion improved methane yield 31.3%-68.0% at thermophilic temperature. • Co-digestion improved methane yield 83.0%-136.5% at mesophilic temperature. • The highest methane yield of anaerobic co-digestion obtained at P/S = 2:1. • NCST and TS of sediment increased with increasing initial TS of substrate. • NCST has a strong negative correlation with the water removal efficiency. The objective of this study is to assess the effects of the mixing ratio on the methane production and digestate dewaterability of co-digestion of pig manure (P) and sludge (S). Batch experiments were carried out at five different P/S mixing ratios at mesophilic and thermophilic temperatures. Compared to sludge anaerobic digestion, co-digestion of pig manure with sludge increased methane yield 83.0%-136.5% at mesophilic temperature and 31.3%-68.0% at thermophilic temperature. The normalized capillary suction time (NCST) and total solids (TS) of sediment (centrifugal dewatering) increased when pig manure proportion of substrate increased. The NCST at thermophilic temperatures (4.87–17.58 s g−1-TSS) was higher than that at mesophilic temperatures (1.89–10.95 s g−1-TSS). However, the TS of sediment was close at thermophilic and mesophilic temperatures. The results indicated that anaerobic co-digestion of pig manure and sludge at a proper mixing ratio (P/S = 2:1) provides a good choice for energy recovery and land utilization. [ABSTRACT FROM AUTHOR]