Wastewater May Decrease Environmental Impact of Cellulosic Ethanol Production

A University of Illinois study concluded treated wastewater, i.e. effluent, could be just as efficient as fresh potable water for the production of cellulosic ethanol. If this study's conclusions prove true and the use of wastewater for the production of this fuel could eventually scale, the results could be a far more efficient production of biofuels from agricultural products such as switchgrass, corn stover and yard waste.

Cellulosic ethanol has been touted for years as a potentially huge source of renewable energy, but the economics and efficiency are not quite there. Several factors are impeding cellulosic ethanol’s emergence as a viable alternative to conventional fuels: the food vs. fuel debate; questions over reliable sources of feedstock; high start-up costs; and the amount of water needed to produce such fuel.

Divya Ramchandran, who wrote the study as his master’s thesis, noted the water efficiency issue: the production of ethanol from corn requires three to four gallons of water for each gallon of ethanol produced; that ratio spikes up to six to 10 gallons of water for each gallon of cellulosic ethanol. In world more stricken by drought, such ratios are a huge hurdle for cellulosic ethanol--and investors--to overcome.

Ramchandran looked at two different kinds of filtered effluent sourced from different municipalities in Illinois and compared them to deionized water as a control sample. Using Miscanthus, a genus of perennial grasses native to Africa and southern Asia as a substrate, Ramchandran found the treated wastewater used to process the grasses resulted in a final ethanol concentration similar to what resulted in the control sample’s treatment.

This study is only a first step in the search for more water efficient processes to produce cellulosic ethanol. Ramchandran calls for further study on the economics of installing wastewater treatment units at such ethanol plants. More evaluations of the impacts of using treated wastewater on pretreatment, hydrolosis and fermentation are also crucial, as well as further study of the overall efficiency of using effluent water to create fuel out of high-cellulose grasses, woods and agricultural waste.

Should Ramchandran’s work show promise, the future of cellulosic ethanol production could shine brighter, especially since plants used as feedstock for this fuel often grow in water stressed areas from India to the San Joaquin Valley. Some ethanol plants have promised to treat their wastewater and use it for irrigation water, but the possibility of using municipal or agricultural effluent could help this holy grail of clean energy scale without the troublesome impact on local water supplies.

Based in Fresno, California, Leon Kaye is the editor of GreenGoPost.com and frequently writes about business sustainability strategy. Leon also contributes to Guardian Sustainable Business; his work has also appeared on Sustainable Brands, Inhabitat and Earth911. Most recently he explored children’s health issues in India with the International Reporting Project. You can follow Leon and ask him questions on Twitter or Instagram (greengopost).

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