Effect of enzymatic pretreatment on anaerobic co-digestion of sugar beet pulp silage and vinasse

Results of sugar beet pulp silage (SBPS) and vinasse (mixed in weight ratios of 3:1, 1:1 and 1:3, respectively) co-fermentation, obtained in this study, provide evidence that addition of too high amount of vinasse into the SBPS decreases biogas yields. The highest biogas productivity (598.1 mL/g VS) was achieved at the SBPS-vinasse ratio of 3:1 (w/w). Biogas yields from separately fermented SBPS and vinasse were by 13% and 28.6% lower, respectively. It was found that enzymatic pretreatment of SBPS before methane fermentation that caused partial degradation of component polysaccharides, considerably increased biogas production. The highest biogas yield (765.5 mL/g VS) was obtained from enzymatic digests of SBPS-vinasse (3:1) blend (27.9% more than from fermentation of the counterpart blend, which was not treated with enzymes). The simulation of potential biogas production from all the aforementioned mixtures using the Gompertz equation showed fair fit to the experimental results.