Natural freezing-thawing pretreatment of corn stalk for enhancing anaerobic digestion performance

Natural freezing-thawing (NFT) was proposed as a low energy input and alternative pretreatment method for high biomethane production from corn stalk (CS) by anaerobic digestion (AD). The CS was pretreated by freezing-thawing in winter season using different pretreatment time periods (7d, 14d, 21d and 28d) and solid-toliquid ratios (1:2, 1:4, 1:6, 1:8 and 1:10). The results showed that CS pretreated for 21d coupled with a solid-toliquid ratio of 1:6 achieved the best result among all pretreatment conditions. In this case, the biomethane yield and VS removal rate of CS reached the highest values of 253 mL.g(vs)(-1) and 58.6%, respectively, which were 40.5% and 27.4% higher than that of the untreated. It was also found that the predominant bacterial and archaeal at genus level in AD were Clostridium_sensu_strictoi (36.1%) and Methanobacterium (54.0%), respectively. This study provided that NFT is a simple pretreatment strategy for efficient AD bioconversion of CS to biomethane.