Avaliação de lodo anaeróbio e dejeto bovino como potenciais inóculos para partida de digestores anaeróbios de resíduos alimentares

Abstract

The proper treatment and disposal of municipal solid waste has been characterized as a challenge, due to the percentage of the organic fraction in its composition. In this context, decentralized solutions arise as very attractive alternatives and the use of anaerobic digesters for the treatment of the organic fraction of solid waste in Brazil is expected to increase in the coming years. This study aimed to evaluate the adaptation potential of the inocula anaerobic sludge and cattle manure at anaerobic degradation of food waste produced in a university restaurant. The anaerobic sludge was collected from an UASB reactor treating domestic sewage, while fresh cattle manure (excreta + urine) was collected in a small farm corral with milk production. Anaerobic biodegradation tests with and without mechanical agitation were conducted using 250 mL reactor flasks incubated at 35 °C, considering the following residue/inoculum ratios (R/I): 0.1, 0.2 and 0.5 gTVSresidue.gTVSinoculum-1. The anaerobic sludge adapted immediately to the organic waste, with increasing methane production being observed already in the first days of the tests. On the contrary, methane production in the reaction flasks inoculated with bovine manure was observed only after approximately 20 days of experiment. Most samples in trials without stirring produced biogas with methane content between 50 and 80 %, except for the R/I ratio of 0.5 gTVSresidue.gTVSinoculum-1, whose content was low or zero and acidification conditions were checked. Increased methane yield and higher production rates were observed with successive feedings, which is indicative of acclimation of the inocula to the residue and of the potential use of anaerobic sludge and cattle manure for start up of anaerobic reactors treating food waste.