Biomethane enhancement from corn straw using anaerobic digestion by-products as pretreatment agents: A highly effective and green strategy

The development of biogas projects feed by lignocellulosic biomass has been constrained by the high cost of pre- and post-treatment. In this study, a novel strategy for pretreatment by using two by-products, i.e., CO2 and liquid digestate (LD), generated from anaerobic digestion (AD) was developed to overcome these shortcomings. Results showed that corn straw pretreated in LD pressurized under 1 Mpa CO2 at 55 degrees C resulted in increased glucose and xylose contents and a 9.80% decrease in cellulose crystallinity. After 45 days of AD conversion, the methane yield increased by 50.97% compared with untreated straw. However, pretreatment in LD pressurized under 1 Mpa CO2 at 170 degrees C produced 5- hydroxymethylfurfural and furfural, which led to a decrease in methane production from the straw in the subsequent AD conversion. The alteration of the microbial community in the pretreated slurry at 55 degrees C was another potential contributor to the enhanced performance of AD.

Automated summary

The study demonstrated that pretreatment with CO2 and liquid digestate from anaerobic digestion can improve the glucose and xylose content of corn straw, reduce cellulose crystallinity, and increase methane yield. However, high temperature pretreatment resulted in the production of inhibitors that decreased methane production during subsequent anaerobic digestion. The changes in microbial community in the pretreated slurry at lower temperature were found to enhance the overall performance of anaerobic digestion.