Co-digestion of deep bedding and wastewater from pig farming: A new strategy for bioenergy increase and biofertilizer recovery.

ABSTRACT

In the present study, a pilot-scale plug flow reactor was used for anaerobic co-digestion of swine wastewater (SWW) and deep bedding (DB). The reactor was operated with organic loads between 315.6 and 782.8 kgCOD d-1 in winter and summer. The experiment was conducted in 4 phases with the addition of DB in SWW in proportions of 0, 5, 10 and 15 tons. Biogas productions 3 times higher were recorded when 15 ton of DB were applied, generating 634.5 kWh d-1 of bioenergy in summer and 267 kWh d-1 in winter. Application of DB in winter promoted stability in biogas production. CH4 concentrations from 60 to 68% were recorded in winter and from 61 to 72% in summer. Methane yield was maximum in summer with application of 15 ton of DB (0.343 m3 KgCODRem-1). Removals of volatile solids and COD were within the ranges of 60-70 and 61-84%, respectively. There was no accumulation of volatile fatty acids (VFAs), nor pronounced decrease of pH in the reactor. The biofertilizer produced in all experimental stages can be used for agricultural cultivation with application rate defined based on the concentrations of Na and K to avoid soil salinization.