Researchers at Purdue University have developed a new front-end processing technique for the production of ethanol from corn that is more environmentally friendly and less costly than conventional wet- or dry-milling processes.
Called the Chen-Xu method after the two developers—Li-fu Chen and Qin Xu—the process produces corn oil, corn fiber, gluten and zein as byproducts of ethanol production. Zein is a protein that can be used in the manufacture of plastics.
With the dry milling process, DDG are produced after fermentation and distillation of ethanol. A centrifuge is used to extract DDG from the residual after ethanol is distilled from the distiller. The co-products of the Chen-Xu method are extracted before fermentation, however, and a centrifuge is not needed.
The Chen-Xu Method produces about 2.85 gallons of ethanol for every bushel of corn processed. That output is slightly higher than current methods, but the same process that creates the ethanol also creates other marketable products. Furthermore, total processing time from corn to ethanol is expected to be less than 24 hours. While fermentation with the dry-milling process can take 48 hours, with the Chen and Xu method, it takes only 4 hours.
Throughput is lower than in conventional processes, however.
Chen said the method also meets federal Clean Air Act standards, eliminating costs that other methods incur in meeting environmental regulations. Both wet- and dry-milling ethanol plants have had environmental problems in the form of pollutants and offensive odor. In 2002, twelve Minnesota ethanol plants were fined by US Department of Justice for violation of Clean Air Act and each agreed to spend more than $2 million for installation of control devices to reduce air pollutants, which were caused primarily by the manufacturing of Dry Distiller Grain animal feed.
In 2003, Archer Daniels Midland agreed to spend $340 million over 10 years for installation of control devices to reduce air pollutants from its processing plants. The EPA estimated about 90% of ADM’s pollution violations stemmed from the company’s corn processing and ethanol operations.
One of the common methods of manufacturing ethanol, called dry milling, is often the cause of air pollutants by drying and storage of DDG, a byproduct of the process. Another method—wet milling—produces an odor because it requires the input of sulfur dioxide. The Chen-Xu Method eliminates both issues, and the only odor comes from the smell of the corn and yeast fermentation.—Li-fu Chen
Using a machine originally designed to make plastics, the Chen-Xu Method grinds corn kernels and liquefies starch with high temperatures. The water input required by wet milling is reduced by 90%, according to Chen. Wastewater output is cut by 95%, and electricity use is reduced by 47%.
The total operating cost of a Chen-Xu Method ethanol plant should be much less than that of a wet-milling plant, and total equipment investment is less than half. And with proper planning and management, total equipment investment should be less than that of a dry-milling plant.—Li-fu Chen
Funding for the work came from industry donations and one year of support from the Value-Added Grant Program of the Indiana State Department of Agriculture. Chen said the next step for the fledgling company is to commercialize the technology worldwide. The technology was licensed to Bio Processing Technology Inc. through the Office of Technology Commercialization, a division of Purdue Research Foundation.