Methane production enhancement from products of alkaline hydrogen peroxide pretreated sweet sorghum bagasse

Abstract

Alkaline hydrogen peroxide (AHP) pretreatment was applied to improve methane production from sweet sorghum bagasse under mesophilic conditions. After the pretreatment (solid-to-liquid ratio of 1 : 10, 2% NaOH at 121 °C for 60 min and then immersing with 5% (w/v) H₂O₂ for 24 h at room temperature), pretreated bagasse, the pretreatment effluent and the pretreatment mixture, together with the untreated bagasse, were used as substrates for methane production under the same volatile solid (VS) loading and digestion conditions. The AHP pretreatment resulted in lignin removal and different degrees of methane production. The methane production of bagasse was improved from 262.1 ± 7.3 mL CH₄ per g VS to 330.4 ± 1.3 mL CH₄ per g VS. The pretreatment mixture and pretreatment effluent could be successfully digested and both of the methane productions were higher than the untreated bagasse, although there were degrees of inhibition. In view of the bagasse recovery during the pretreatment, total methane production from separate digestion of pretreated bagasse and pretreatment effluent was 18.6% more than untreated bagasse based on the same mass of dry sweet sorghum bagasse. The kinetic analysis implied that the Cone model showed a better fit to the experimental data of untreated bagasse, pretreated bagasse and pretreatment effluent, and the Fitzhugh model was better to predict the methane production of the pretreatment mixture. AHP pretreatment could increase the methane production rate of sweet sorghum bagasse. These results will provide a reference to the methane production from AHP pretreated sweet sorghum bagasse in industry.