Use Treated Effluent Water in Bio-ethanol Production
The bioethanol industry has a substantial water usage demand, significantly straining water supplies. About 3 to 4 gallons of water are consumed per gallon of ethanol produced in corn dry-grind plants. In comparison, cellulosic ethanol plants require 6 to 10 gallons of water per gallon.
In dry-grind ethanol plants, water is primarily used in grinding, liquefaction, fermentation, separation, and drying processes. Additionally, heating, cooling, and drying are significant water-consuming steps. In contrast, cellulosic ethanol production involves more water in biochemical conversion than thermochemical conversion. The significant water-consuming steps in biochemical cellulosic ethanol production are pretreatment of cellulosic feedstock, enzyme hydrolysis, and fermentation. With current technologies and improvements, biochemical conversion uses 6 gallons of water per gallon of ethanol, while thermochemical conversion uses only around 1.9 gallons per gallon of ethanol.
It would be greatly beneficial to reduce the strain on water supplies if some of the industry’s effluent water could be reused after treatment to complement the current water consumption. A study by Ramachandran et al. demonstrates that with proper characterization studies and under appropriate conditions, the use of treated effluent water in cellulosic ethanol production is feasible.
Bioethanol production companies can invest in reusing effluent water to reduce their overall water consumption. This approach would benefit both the industries and the environment. It would significantly reduce water utility bills while promoting water conservation.