Enhanced biomethane production from corn straw by a novel anaerobic digestion strategy with mechanochemical pretreatment

Abstract

The biomethane production from lignocellulose via anaerobic digestion has always suffered from low carbon conversion rate, due to the stubborn structure of lignocellulose and the inefficiency of the current anaerobic digestion systems. The integrated two-phase anaerobic reactor can form a highly efficient anaerobic digestion system with an upper acidogenic phase and a lower methanogenic phase. However, the acidogenic phase can be overaccelerated, leading to acidification failure of the whole digestion system. In this study, the acidogenesis liquid digestate (ALD) generated from the acidogenic phase was applied to impregnate corn straw coupled with disc refining (DR) to enhance biomethane production by forming a thorough and stable integrated two-phase anaerobic system. The concentration of volatile fatty acids in the acidogenic phase is adjusted by this pretreatment technology to approximately match the efficiency of methanogenic bacteria in the methanogenic phase. The acetic acid in ALD was proved to be an effective acid to swell lignocellulose and improved the performance of the acid impregnation coupled with disc refining (AIDR) pretreatment. A 47.13% higher biomethane yield was obtained from corn straw after AIDR pretreatment. Moreover, energy conversion efficiency and economic analysis indicated this anaerobic digestion process with AIDR pretreatment had a $ 21.06 ton−1 higher net profit than that without any pretreatment. This novel anaerobic digestion process creates a synergistic processing technology that integrates biomass pretreatment with a two-phase anaerobic digestion system, resulting in destroying the compact structure of lignocellulose, enhancing biomethane production efficiency, and improving the economic competitiveness of biomass conversion to biomethane.