Improvement of anaerobic fermentation of rice straw by integrated wet-milling and ammonia pretreament.

An integrated wet-milling and ammonia pretreatment was proposed to improve the efficiency of anaerobic fermentation of rice straw.The rice straws pretreated by cutting,grinding and wet-milling were subjected to single-phase anaerobic fermentation to investigate the characteristics of reaction rate and pH of fermentation feedliquor,and effects of particle size and ammonia concentration on reaction rate and gas yield.The experimental results showed that the anaerobic fermentation of rice straw could be divided as early,middle and late steps.The pH of fermentation feedliquor decreased in the early step and was 6.5-7.0 in the middle and late steps.Particle size and ammonia concentration had significant effects on the reaction rate and the gas yield.The average gas production rate and the gas yield were 7 mL/(g·d) and 216 mL/g for the cut rice straw.The average gas production rate was increased to 14 mL/(g·d),and the gas yield was increased to 378 mL/g by the wet-milling with 0.2% ammonia.