Methane enhancement by the co-digestion of soybean straw and farm wastewater under different thermo-chemical pretreatments

Abstract

This work aims to enhance and optimize the methane production by anaerobic co-digestion of soybean straw (SS) and farm wastewater. Thermo oxidation and alkali pretreatments were applied during the present study. The effects of chemical composition were investigated and the influence of thermo-chemical pretreatment on methane production by SS with wastewater was evaluated by Batch and semi-continuous experiments. All pretreatments were found significant (P < 0.05) to enhance the lignocellulosic degradability and methane yield. The highest methane yield which was recorded by 2% wet NaOH presoaking prior at 4.5% H2O2, 100 °C for 30 min pretreatment was 206 ml/g·VS which was 62% higher than the untreated straw during batch experiments. The synergistic effects were demonstrated during the anaerobic co-digestion of soybean straw and farm wastewater and the digestion period was shortened to almost half. In addition, a range of organic loading rate (OLR), (1.5–7.5) g·VS·L−1·d−1 was applied for the semi-continuous experiments and OLR of (3–6) g·VS·L−1·d−1 was concluded as the optimum OLR with the highest methane production capability of 194 ml/(g.VS.L.d).