Anaerobic mono-digestion of sugarcane trash and bagasse with and without pretreatment

Abstract

The effect of organic loading on process performance and methane yields during anaerobic mono-digestion of sugarcane trash (ST) and sugarcane bagasse (SB) with and without dilute sulphuric acid impregnated steam explosion was investigated. At first, biochemical methane potential (BMP) of ST and SB was performed at 37 °C in batch assays with an inoculum to substrate (ISR) ratio of 2 on VS basis. Methane yields of 161.8 ± 4 and 187.9 ± 2.4 N mL g−1 VSadded were obtained for ST and SB, respectively. These yields were 55.6 and 53.8 % of the theoretical methane potentials for ST and SB respectively. Later, semi-continuous reactor experiments were conducted using four stainless steel reactors with working volume of 10 L and hydraulic retention time (HRT) of 35 d at 37 °C. Reactors were fed with untreated ST, untreated SB, steam exploded trash (TT) and steam exploded bagasse (TB). In all four reactors, methane production increased with increase in organic loading rate (OLR) from 1.5 to 2.5 gVS L-1 d-1. However, higher methane yields were noticed in TT (226 ± 37 NmL g-1VSfed) and TB (236 ± 22 NmL g-1VSfed) than for ST (121 ± 24 mL g-1VSfed) and SB (148 ± 25 mL g-1VSfed). Increase in OLR from 2.5 to 3.5 gVS L-1d-1 resulted in decreased methane yields and pseudo state stable conditions. Thus, steam explosion with dilute H2SO4 catalyst can improve the methane yields of both ST and SB.