Novel low-cost pre-treatment material for enhancing the methane yield during anaerobic digestion of lignocellulosic biomass feedstocks: Experimental and kinetic study

Trona, a low-cost and commonly available evaporite mineral was investigated as a novel pre-treatment material for enhancing the methane yield during the anaerobic digestion (AD) of grass silages. The results from BMP tests indicated that reactors fed with hot water pretreated Guinea grass and reactors fed with the grass pretreated with 5 mg/L and 10 mg/L Trona achieved maximum methane production rates (Umax) of 28.0, 56.4 and 58 N mL CH4/d, respectively, signifying an increase in Umax from Trona-pretreated grass by 201% and 207%, compared to the control reactors. The degradation yields in the three pairs of reactors were 68%, 79% and 75%, respectively. Kinetic modelling showed that the substrate hydrolysis rates (kh-values) were 0.32, 0.35 and 0.34 d−1, respectively, indicating that Trona-pretreatment enhanced the hydrolysis of Guinea grass. A step-change in temperature significantly affected methane yield. Kinetic models also satisfactorily predicted methane productivity in the reactors with >92% prediction accuracy. These results demonstrate that Trona pretreatment and mesophilic temperatures provided accelerated hydrolysis of biomass contents which enhanced methane production.