55 / 2021-06-30 09:15:05

Improving anaerobic digestion of corn straw by using solid-state urea pretreatment

Corn straw; Anaerobic digestion; Urea pretreatment; C/N ratio; Methane yield.

The resistant structure and high carbon/nitrogen ratio (C/N) of crop residues are the barriers during their anaerobic digestion (AD). Solid-state urea pretreatment was developed in this study, which could pretreat corn straw and adjust C/N ratio simultaneously for the downstream AD of corn straw. Results showed solid-state urea pretreatment was efficient in lignin removal and achieved the highest lignin reduction of 7.06% with C/N ratio=15 during pretreatment. Scanning electron microscopy demonstrated the destruction of the dense structure by pretreatment, which benefited the hydrolysis of corn straw. The cumulative methane yields of the pretreated corn straw ranged from 234.07 to 250.03 mL/g VS, which were obviously higher than that of the untreated corn straw. The maximum methane yield of 250.03 mL/g VS was achieved with C/N=15, which was 23.91% higher than that of the untreated group. In addition, AD digestates from the pretreated groups had 9.62% higher nutrients than that from the untreated group. Therefore, the solid-state urea pretreatment can impact the C/N ratio of corn straw while showing a positive effect on AD of corn straw.