Nanobubble Technology Application for Energy Recovery from Rice Straw: Enhancement Process and Mechanism

Abstract

This study explored the efficiency of CO2-, N2- and H2-NBW application in anaerobic digestion (AD) of rice straw, focus on methanogenic performance and metabolic pathway, and revealed the underlying mechanisms. The results showed that NBW addition enhanced total methane production by 4.22% to 7.79% compared to the control group. Mechanism investigations revealed that NBW increased the degradation of cellulose and hemicellulose by breaking the lignin-coated structure, leading to higher soluble carbohydrates (6.27%-11.13%), α-glucosidase activities (12.32%-23.72%), VFAs (4.39%-24.50%), and cumulative H2 yield (74-94 times). In addition, the modified Gompertz model and the first-order kinetic analysis indicated that NBW could improve the reaction rates of AD and H2 production stages, with CO2-NBW demonstrating the most prominent effect. Based on the analysis, it can be concluded that NBW mainly promotes hydrolytic acidification rather than methane production. The results suggest that NBW is beneficial in enhancing the AD process of cellulosic biomass.

Keywords: nanobubble water, anaerobic digestion, rice straw, energy production, mechanism