The transition temperature (42 °C) from mesophilic to thermophilic micro-organisms enhances biomethane potential of corn stover

Highlights: • The highest BMP was achieved at 42 °C for batch corn stover AD. • Multi-peaks in daily methane yield curves were observed. • The pH decline to 6.0 and longer lag time at 42 °C acted as a natural pretreatment. • Main driver of BMP enhancement at 42 °C was caused by natural pretreatment. Mesophilic and thermophilic digestion has long been considered as preferred temperature ranges for anaerobic digestion. However, in this study, the effects of temperatures (37, 42, 47, and 55 °C) on the biomethane potential of corn stover were conducted with batch experiments, and the highest biomethane potential was at 42 °C. It was inferred that the change of feed materials, e.g., pretreatment caused by acidification (pH 6.0) during the lag time (4 days), was the main driver for higher biomethane potential. The natural pretreatment stimulated by a slight digestive temperature increase to 42 °C can enhance the biomethane potential of corn stover without adding extra acid. Meanwhile, metabolic pathways of methanogens changed from acetoclastic to mixotrophic and hydrogenotrophic methanogenesis. Based on these results, the transition temperature (42 °C) from mesophilic to thermophilic micro-organisms could be a promising option for corn stover anaerobic digestion.