Sustainability of winery waste anaerobic digestion: digestate characterization and treatment technologies evaluation

Abstract

Winery wastes produced by a cellar producing approximately 31,579,881 liters of wine per year. On average, 542.3 kg of waste activated sludge (9% dry matter) and an average of 2 g of wine lees per liter of wine produced, i.e. 173.7 kg of wine lees, were produced daily. Much organic waste comes out during wine production. The biodegradability of wine wastes is high, therefore direct disposal is environmentally hazardous. This waste could be a good substrate for anaerobic digestion (AD) process, with a direct renewable energy production (biogas) and reduces green house emission. the waste from this process is called digestate, that could be used as fertilizer. In this study, we used sludge and wine lees as feed for AD system in mesophilic and semi-continuous reactor condition. Hydraulic retention time was 20 days. The process was stable for a long time at 37 °C and the average daily biogas production was 1.486 m3/kgCODfed, with a methane gas production of 55-60%. On this experimental AD system, it was performed an economical analysis in terms of the heat used to maintain the highest temperature. Considering the real productions of the company and applying the conditions used in the present work (mesophilic) it is possible to obtain about 77 MWh/y of electricity, with a saving of about 70% on the expense item related to the disposal of composting sludge.