Effect of pretreatment with efficient microorganisms on anaerobic digestion of rice drying residue

Abstract

Rice drying generates large amounts of impurities which has been previously studied for biogas production with unfavorable results due to its high lignocellulosic content. This research aimed to assess the effect of the pretreatment and bioaugmentation with efficient microorganisms on the anaerobic digestion of rice drying residue, and the kinetics of methane production. For the study, rice drying residues were pretreated for 48 hours with efficient microorganisms diluted 1:100, in a relation of 18 mL gVS-1 of substrate; while for bioaugmentation microorganisms were added directly to the reactors. The kinetic behavior of the digestion process was described through four models of first and second order. The highest methane yield was obtained with pretreated residues (363.7 LN kgVS-1), being 9.9% higher than that of the substrate without pretreatment. Bioaugmentation did not show significant differences. All the models fitted well with the experimental cumulative methane yield data, but the Hill modified model had the best fit in all cases. The study shows that the use of efficient microorganisms is an attractive option to increase waste degradation in anaerobic digestion processes.