Quantification, characterization, and anaerobic digestion of sheep manure: The influence of diet and addition of crude glycerin

Abstract

The objective of this study was to evaluate the influence of roughage‐to‐concentrate ratio on quantification and characterization of sheep manure, and to verify whether the addition of crude glycerin improves the efficiency of the anaerobic digestion process. The characterization study was carried out with two treatments (diet 1 with 40% roughage and 60% concentrate and diet 2 with 60% roughage and 40% concentrate) and 12 replicates per treatment. Parameters evaluated were as follows: production of manure, total solids (TS), volatile solids (VS), most probable number (MPN) of total (TC) and thermotolerant coliforms (TTC), chemical oxygen demand (COD), and residue coefficient. The digestion test was performed in batch digesters that were loaded with sheep manure with the doses of crude glycerin: 0, 3, 6, 9, 12, and 15% in the substrate. The process efficiency was measured by the reduction of TS, VS, and COD as well as the production of biogas. No differences were observed for the production of TS and manure among the diets. The contents of VS, COD, and MPN of TC and TTC were greater in manure from animals fed with higher concentrate ratio. Multiple linear models were generated according to the reductions of VS, TS, COD and production and potential of biogas and methane production and hence, both the additions of concentrate in the diet and crude glycerin in the codigestion influenced, in a positive way, the removal organic load in digesters. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1038–1043, 2015