Biogas production from anaerobic co-digestion of cow dung and lignocellulosic wastes

Abstract

A series of study on biogas potential test and the effect of organic loading rate (OLR) and NaOH pretreatment concentration from the co-digestion of cow dung (CD) with corn husk (CH), palm oil leaf (POL), and grass-cutting (Gr) was conducted. Biogas potential test observation was performed with feeding rate of organic dry matter set to 238 g volatile solid (VS)/day-1 (FRBPT-1), 476 g VS/day-1 (FRBPT-2), and 714 g VS/day-1 (FRBPT-3). The co-substrates (CH, POL, and GR) were soaked with NaOH solution at 3 days (NT3) for FRBPT-1, 4 days (NT4) for FRBPT-2, and 5 days (NT5) for FRBPT-3. The result showed that CH has the highest yield of biogas for all three set of parameters at 2.27, 1.51, and 2.06 L biogas/Kg VS.day-1 on FRBPT-1/NT3, FRBPT-2/NT4, and FRBPT-3/NT5, respectively. A subsequent study on the optimization with the same variables was conducted, by Face-Centered Central Composite Design (CCF) as the experimental design. OLR was set at 25, 35, and 45 g VS/L.day-1 per digester, denoted as FR1, FR2, and FR3, respectively. The pretreatment concentration of NaOH was given at 25, 35, and 45%, denoted as N1, N2, and N3, respectively. The maximum yield obtained was 8.98 L biogas/kg VS.day-1 with 45 g VS/L.day-1 of OLR and 25.0% application of NaOH pretreatment concentration. While the maximum methane content observed was 68.8% by volume, obtained at 45.0 g VS/L.day-1 OLR and 45.0% NaOH pretreatment concentration.