Using electrolyzed water rather than harsh chemicals could be a more effective and environmentally friendly method in the pretreatment of ethanol waste products to produce an acetone-butanol-ethanol fuel mix, according to research conducted at the University of Illinois.
When ethanol is produced, distiller’s dried grain with solubles (DDGS) is a waste product. The DDGS is primarily used as animal feed, but researchers are searching for ways to extract the sugar and ferment it to produce an acetone-butanol-ethanol (ABE) fuel mix. One obstacle has been in the pretreatment phase.
The glucose in DDGS is stuck together, forming cellulosic corn fiber, but the structure is very tough. It forms a kind of crystalline structure which is very difficult to break, said U of I researcher Hao Feng.
In order to get the glucose out, we need to somehow destroy the structure. Normally people use a strong acid such as sulfuric acid, or a strong lime base, to loosen it, making holes in it. Once the structure is destroyed, we use enzymes to cut the chain of glucose to get glucose that can be used for fermentation.
When you break down the structure, sometimes you can produce compounds which are not friendly to the microorganisms used in fermentation. These are what we call inhibitors—they kill the microorganisms like the Baker’s yeast used to make ethanol.—Hao Feng
Feng, a University of Illinois food scientist, has been using electrolyzed water in his lab to kill bacteria such as E. coli on fresh fruits and vegetables. Electrolyzed water is created in a reactor which allows the separation of the cathodic and anodic solutions, one acidic and one alkaline.
Realizing that these similar properties in sulfuric acid and lime are used to pretreat DDGS in fuel production, Feng’s lab conducted experiments comparing the use of electrolyzed water to the traditional chemicals.
Using the strong sulfuric acid method, there was no fuel produced. The toxic compounds killed the microbes that produce acetone-butanol-ethanol mix completely. Using the alkaline sodium hydroxide as a base, after 60 hours, the acetone-butanol-ethanol production was also relatively low. But using acidic electrolyzed water, at about 20 hours the fermentation process began producing the acetone-butanol-ethanol mix. This is an example of less inhibitor production with electrolyzed water compared with the traditional method.—Hao Feng
Feng said that this new technique also eliminates the production step of removing the acid. “The other advantage of this method is that the traditional method produces a large quantity of solid waste that needs to be handled, and some sugars get consumed in the process as well. We want to maximize the sugar yield so we can maximize the ethanol yield.”
At this point, the process has been successful on the scale of a small laboratory; the next step is to look at the economic feasibility of the process.
Part of the results from the study is published in a 2009 issue of Transactions of the American Society of Agricultural and Biological Engineers (ASABE). The work is done in collaboration with Hans Blaschek’s lab with participants including Bin Wang, Thaddeus C. Ezeji, Zhen Shi, Xiaojuan Wang, and Yi Wang. The research is supported by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service and the US Department of Energy.
B. Wang, T. Ezeji, Z. Shi, H. Feng, H. P. Blaschek (2009) Pretreatment and Conversion of Distiller’s Dried Grains with Solubles for Acetone-Butanol-Ethanol (ABE) Production. Transactions of the ASABE. 52(3): 885-892.