Refining of the solid fraction of sheep feces digestates from an anaerobic digester

Abstract

Anaerobic digestion is a technology used in the degradation of organic waste, with the possibility of obtaining products such as biogas and digestates, which have significant nutrient concentrations. However, using them without any prior treatment can cause various problems, due to the presence of unstabilized organic matter and excessive concentrations of nutrients reaching phytotoxic levels, as well as water and air contamination. Therefore, in this work, we present a refining process of solid digestates from a biodigester fed with sheep feces, by means of vermicomposting, in combination with plant waste, and using earthworms of the species E. andrei and E. fetida. The digestate values at the end of the vermicomposting showed to be within optimal ranges of electrical conductivity, with values ≤4 dS/m. The pH values were between 5,39 and 7. The percentage of organic matter was between 20 and 50%. It could be proven that the refining process increased the concentration of K for groups F 50:50, F 75:25, and A 75:25, with a value of P = 0,0001. Treatments with E. fetida showed the highest concentrations (g/L) of N = 2,71 ± 1,10, P = 0,89 ± 0,69 and K = 4,01 ± 1,57. The importance of giving added value to the products generated during anaerobic digestion processes contributes to better yields and quality in their use and commercialization.