Ensiling of Fruits and Vegetables Wastes from a Food Supply Center for the Improvement of Methane Production

Abstract

The current study investigated the methane generation potential from the anaerobic bio-digestion of fruits and vegetables wastes (FVW) generated in a food supply center in Brazil. This study used the ensiling process as a pre-treatment for this lignocellulosic biomass aiming to improve the methane yield. FVW were mixed in the same proportion (0.2 g on a volatile solid basis per residue) and ensiled at room temperature (≈25 °C) for 30 and 55 days (samples Ensil-30 and Ensil-55). The ensiled and untreated waste samples were inoculated with industrial granular sludge and incubated at 37 °C (mesophilic conditions) until there was no more significant biogas generation. The experimental data were fitted to the First-order, Cone, and Modified Gompertz kinetic models. The methane yield of the ensiled samples was ≈21% higher than the methane yield of the untreated sample. Considering the ensiled samples, the methane generation was statistically the same (52.0 and 51.3 NmL/gvs for samples Ensil-30 and Ensil-55, respectively), that is, duplication of the storage period failed to increase the methane volume. Although the results indicated that the ensiling of FVW could be a viable strategy to improve the biodegradability of the lignocellulosic biomass and promote its valorization as an energy source, a preselection of the agricultural residues that will feed the biodigesters is suggested. Considering the process conditions and the residues used, the substrate characteristics were shown to carry out a key role in the bio-digestion processes and consequently in methane generation.