Biogas Production from a Highly Organic Loaded Winery Effluent Through a Two-Stage Process

Abstract

The application of a two-stage process to effectively treat winery effluents containing a high concentration of organic matter, measured as chemical oxygen demand (COD), was studied in laboratory scale reactors. The effect of the organic loading rate on either the acidogenic or the methanogenic reactors performance was evaluated. The first stage reached an organic load of 220 kg COD/m3/d with 12% of organics removed and volatile fatty acid (VFA) production rate of 27 ± 1.5 kg COD/m3/d, where acetate was the main VFA. The importance of this investigation results in an efficient conversion of the organic matter to VFA obtained in the acidogenic phase avoiding the acidification in the methanogenic stage. Hydrolysis of the particulate material was conducted regardless of the high rate of VFA production. During the methanogenic stage, organic loading rates up to 26 kg COD/m3/d were efficiently treated, and methane production rates were up to 5.5 m3CH4/m3/d. Maximal methane yields reached 326 mL CH4/g COD. It was demonstrated that it was feasible to treat winery effluents containing high initial organic matter (up to 220 g COD/L) by using a two-stage (acidogenic followed by methanogenic) process. Such configuration reduced the initial organic matter by up to 97% and generated methane with yields close to the theoretical value.