Influence of pretreatment with Fenton’s reagent on biogas production and methane yield from lignocellulosic biomass

Biomass from Miscanthus giganteus, Sida hermaphrodita and Sorghum Moensch was treated with Fenton’s reagent for 2 hours under optimal conditions (pH = 3, mass ratio of [Fe2+]:[H2O2] equals 1:25 for Miscanthus and Sorghum and 1:15 for Sida). The degrees of delignification were 30.3%, 62.3% and 48.1% for the three plant species, respectively. The volatile fatty acids concentration after chemical pretreatment was high enough for production of biogas with a high methane content. Combined chemical oxidation and enzymatic hydrolysis with cellulase and cellobiase led to glucose contents of above 4 g/L. Among the tested plants, the highest biogas production (25.2 Ndm3/kg TS fed) with a 75% methane content was obtained with Sorghum Moensch. The results of the three-step process of biomass degradation show the necessity of applying a chemical pretreatment such as oxidation with Fenton’s reagent. Moreover, the coagulation of residual Fe3+ ions is not required for high biogas production.