Treated wastewater effluent could be a viable alternative to potable freshwater for cellulosic ethanol production, according to a study by the University of Illinois Urbana-Champaign. The study, “Use of Treated Effluent Water in Cellulosic Ethanol Production,” was funded in part by the Illinois Sustainable Technology Center.
The use of non-food cellulosic feedstock for ethanol fuel production has a number of advantages, including lowering greenhouse gas emissions and reducing cost pressure on food and feed markets, the study says. Drought-resistant cellulosic feedstock also can be grown on land unsuitable for row crops.
However, cellulosic ethanol plants consume large amounts of water. Dry grind ethanol plants currently use around three to four gallons of water per gallon of ethanol produced, whereas cellulosic ethanol plants are estimated to consume around six to 10 gallons of water per gallon of ethanol produced, the study says.
The study evaluated the effects of two different types of filtered treated effluent on the rate of fermentation and final ethanol yield from a pure cellulosic substrate. The final ethanol concentrations with the two types of effluent and a control sample using de-ionized water were similar, suggesting that under appropriate conditions the use of treated wastewater is feasible, according to the study.
A report released in February by Lux Research said demand for biomass is expected to triple by 2030, driven by biofuel mandates and growth in the biochemicals industry, placing pressure on available feedstocks.
Biofuel mandates, which require large masses of sugars, cellulosic biomass and waste feedstocks, will put stress on available biomass in several regions, the Lux Research report said. For instance, the EPA is proposing a 62 percent increase in the amount of cellulosic biofuels that refiners must blend into their gasoline and diesel, despite a federal court’s decision in Febraury to strike down the agency’s 2012 standard for the fuel.