Effect of pretreatment with microbial consortium on anaerobic digestion of rice drying residue

Residues from rice drying are an important source of lignocellulosic biomass, with the potential to be used in anaerobic digestion processes and contribute to fossil fuels substitution. However, due to its recalcitrant structure, bioconversion remains a challenge. This research aimed to assess the effect of pretreatment with a microbial consortium on hydrolysis, methane yield, and anaerobic digestion kinetics of this residue.

For the study, a new consortium (MC) was obtained and characterized. This consortium was then used (diluted 1:100) to pretreat the substrate for five days, using two ratios (12 and 18 mL of MC g volatile solids (VS)^-1 of substrate). The degradation capacity was evaluated through the reducing sugar content released daily, in order to select the optimal time and ratio. The kinetic behavior in anaerobic digestion was described by four models: Roediger, Hill, Modified Gompertz and Transference Function.

Characterization revealed the presence of bacteria with cellulolytic activity in the consortium. The highest methane yield was obtained for pretreated residues (190.8 L_N kgVS^-1) after 24 h of pretreatment at the ratio of 12 mL gVS^-1, which was 13.9 % higher than the untreated substrate. All models fit well with the experimental cumulative methane yield data, but Roediger model showed the best fit in all cases.

This research demonstrated that pretreatment with a microbial consortium significantly enhanced hydrolysis, methane yield, and anaerobic digestion kinetics of the rice drying residue. The findings highlight its potential to optimize biogas production, offering a sustainable strategy for improving waste-to-energy conversion efficiency.