NaOH-urea pretreatment enhanced H2 and CH4 yields via optimizing mixed alkali ratio, pretreatment time, and organic loading rate during anaerobic digestion of corn stover

This work studied the impact of NaOH-urea pretreatment on corn stover for H2 and CH4 production through two-stage anaerobic digestion. Results showed that the NaOH-urea pretreatment process improved CH4 production more significantly compared to H2. Optimized by Box-Behnken design (BBD) experiments, the CH4 cumulative yield was increased by 34.2 % at NaOH: urea = 3.2: 26.8, time = 15.7 min, and organic loading rate (OLR) = 23.4 w/v. Microbial community diversity analysis showed that the hydrogen and methane production stages formed communities dominated by Bacteroidales and Methanobacteriales, respectively. In addition, NaOH-urea pretreatment enhanced the metabolite energy recovery efficiency by 28.5-40.9 %. Finally, the return on in-vestment (ROI) of the NaOH-urea pretreatment process reached 26.1 % with significant economic benefits. This research proposed a chemical pretreatment process for anaerobic digestion of corn stover by optimizing the pretreatment conditions of NaOH-urea.