Biological thermophilic post hydrolysis of digestate enhances the biogas production in the anaerobic digestion of agro-waste

A thermophilic post-hydrolysis process was applied to the effluent digestate of an anaerobic digester treating agm-waste to further solubilize biorecalcitrant organic polymers and, by recirculating back hydrolysate to the anaerobic reactor, increase the biogas production. The thermophilic reactor operated at 3 days hydraulic retention time determined a clear increase in the concentrations of both soluble organic matter (as COD) and volatile fatty acids: concentrations increased by 25% and 65%, respectively. As a consequence, the recirculation of this post-treated stream to the digester determined an increase in biogas production of 30% on average with respect to the case without thermal post treatment.