Dairy cow effluent: enzymatic hydrolysis as pretreatment of anaerobic digestion

Dairy cow effluent was subject to an enzymatic pre-treatment prior to anaerobic digestion by applying two different commercial enzymes, mainly exhibiting hemicellulase (He) or laccase activities (La), applied at different dosages. Comparatively, laccase provided higher glucose liberation than hemicellulase, with the highest yield (44%) achieved when applying the highest laccase dosage (1.5 g/100 g cellulose) whereas the lowest yield (14%) was obtained with the lowest hemicellulase loading (1.5 mL/g biomass). Accordingly, anaerobic digestion was more efficient following pre-treatment with the highest laccase dosage, with increased biogas production (366 mL, 65% CH4). The present results demonstrate that the enzymatic pre-treatment provided significant improvement on the anaerobic conversion of recalcitrant effluents into biogas/methane, with increased biogas production in comparison with the use of the raw cattle effluent. The positive impact of the enzymatic pre-treatment on the anaerobic conversion efficiency does not seem to be due to the hydrolysis of the effluent constituent polysaccharides but probably result from a structural rearrangement.