Valorization of vinasse as broth for biological hydrogen and volatile fatty acids production by means of anaerobic bacteria

Abstract

Abstract: Vinasse is the liquid waste removed from the base of sugarcane ethanol distillation columns at a ratio of 12-15 liters per liter of alcohol, resulting in an estimated production of approx. 370 billion liters in 2012/2013 in Brazil. Vinasse has a low pH and high chemical oxygen demand, which can cause land desertification when indiscriminately used as fertilizer. Also, underground water contamination is being observed in some regions. We evaluated the potential of vinasse as nutrient source for biohydrogen and volatile fatty acids production by means of anaerobic consortia. Two different vinasse-based media were proposed, using sugarcane juice or molasses as carbon source, and were compared to fermentation in a sucrose-supplemented medium. Pure cultures (4) and consortia (7) were cultured in the propose media and evaluated for volatile fatty acids (VFAs) and biohydrogen production. The consortium LPBAH1 was selected for fermentation of vinasse supplemented with sugarcane juice, resulting in a higher H2 yield of 7.14molH2/molsucrose and hydrogen content in biogas of approx. 31% after process optimization. Similarly, the optimized process using the consortium LPBAH2 resulted in 3.66 molH2/molsucrose and 32.7% hydrogen content in biogas. The proposed process is of great importance for giving a more rational destination to vinasse and expanding Brazilian energy matrix, reducing the dependence of fossil fuels.