Evaluation of Anaerobic Digestion of Verdejo Lees from an Ecological Crop

The winemaking industry generates large volumes of highly polluting organic waste (grape marc, lees, wastewater) from the processing of grapes to produce white wine (Verdejo). Therefore, the sustainable management of the generated waste is crucial. Concretely, lees with a high nutritional value were found to be a highly biodegradable waste (approximately 53%) by methanogenic microorganisms. The anaerobic digestion technology is of interest to produce renewable energy, in the form of methane, and to recycle the stabilized organic matter and other essential nutrients in agricultural soils. Testing was conducted on a laboratory-scale at mesophilic conditions. Given the lees belong to an ecological crop, the heavy metals content in this waste was lower than other studies, and consequently more beneficial for the maintenance of methanogenic archaea. According to the control variables evaluated in this study, the anaerobic process was stable, showing a mean methane yield of 332 ± 37 mLSTP CH4/g VS without inhibitory signals for the loads up to 3.5 g VS/L.