Steam explosion pretreatment of wheat straw to improve methane yields: Investigation of the degradation kinetics of structural compounds during anaerobic digestion

• Steam explosion treatment of straw from 140 °C to 178 °C for 30, 60, 120 min.
• Treatment caused a hydrolysis of hemicellulose and the formation of pseudo lignin.
• Investigation of the degradation process of biomass during anaerobic digestion.
• Increasing severity of pretreatment resulted in faster degradation of the biomass.
• Content of pseudo-lignin decreased during the anaerobic degradation experiment.

Wheat straw can serve as a low-cost substrate for energy production without competing with food or feed production. This study investigated the effect of steam explosion pretreatment on the biological methane potential and the degradation kinetics of wheat straw during anaerobic digestion. It was observed that the biological methane potential of the non steam exploded, ground wheat straw (276 lN kg VS−1) did not significantly differ from the best steam explosion treated sample (286 lN kg VS−1) which was achieved at a pretreatment temperature of 140 °C and a retention time of 60 min. Nevertheless degradation speed was improved by the pretreatment. Furthermore it was observed that compounds resulting from chemical reactions during the pretreatment and classified as pseudo-lignin were also degraded during the anaerobic batch experiments. Based on the rumen simulation technique, a model was developed to characterise the degradation process.