Use of Treated Effluent Water in Cellulosic Ethanol Production

The bioethanol industry exerts a significant demand on water supplies. Current water consumption rate in corn dry grind ethanol plants is 3 to 4 gallons of water per gallon of ethanol produced (gal/ gal) and 6 to 10 gal/gal for cellulosic ethanol plants. The main goal of this study was to examine the use of treated wastewater effluent in place of potable freshwater for cellulosic ethanol production. The effects of using two different types of filtered treated effluent; Bloomington- Normal, IL (Residential type) and Decatur, IL (Industrial/Residential Mix type); on the rate of fermentation and final ethanol yield from a pure cellulosic substrate were evaluated. Final ethanol concentration with Bloomington- Normal and Decatur effluent and our control study using de-ionized water were similar, resulting in 4.57 0.22 % v/v (0.36 g/g, db), 4.74 0.13 % v/v (0.37 g/g, db) and 4.55 0.28 % v/v (0.36 g/g, db), respectively. Residual glucose concentrations were <0.04 % w/v at 48 hr in all cases, suggesting complete fermentation. Further study with Decatur effluent using 0.08 mm finely ground Miscanthus as the substrate resulted in a final ethanol concentration of 0.46 0.008 % v/v (0.14 g/g db) which was similar to ethanol concentration of 0.52 0.07 % v/v (0.17 g/g db) obtained with control treatment using de-ionized water. These findings suggest that with proper characterization studies and under appropriate conditions, the use of treated effluent water in cellulosic ethanol production is feasible.