Purdue Researchers Develop New Corn Ethanol Production Method - Reduces Environmental Footprint and Costs

As Green Car Congress (GCC) reports, 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 byproduct of ethanol productions. Zein is a protein that can be used in the manufacture of plastics.

With the dry milling process, distillers dried grains (DDG), an animal feed, 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. In contrast, the Chen-Xu method extracts the co-products before fermentation, eliminating the need for a centrifuge.

The Chen-Xu Method produces about 2.85 gallons of ethanol for every bushel of corn processed, GCC reports. That output is slightly higher than current methods (~2.7 gal/bu for dry-mill and ~2.6 gal/bu for wet-mill methods), and 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, GCC reports. The fermentation step in the Chen-Xu method takes only 4 hours, while it can take 48 hours in the dry-milling process.

According to GCC, throughput is lower than in conventional processes, however. [This doesn't make sense to me though: if processing time is considerably shorter, how can throughput be lower?]

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 often have 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, according to GCC. The EPA estimated about 90% of ADM’s pollution violations stemmed from the ag. giant's corn processing and ethanol operations.

According to Li-fu Chen:

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.

Using a machine originally designed to make plastics, the Chen-Xu Method grinds corn kernels and liquefies starch with high temperatures. According to Chen, the new process reduces water use by 90% compared to wet milling. Wastewater output is also cut by 95%, and electricity use is reduced by 47%.

Chen:

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.

According to GCC, 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.


This seems to be an excellent incremental improvment to the ethanol production process. The reduced emissions, water use, wastewater discharge and electricity consumption will all reduce the environmental footprint of ethanol production from corn.

I wonder what the direct energy inputs for this new process are like compared to wet and dry milling processes. Coal or natural gas consumption for process energy at ethanol production plants is the main contributor to fossil energy inputs and greenhouse gas emissions in a well-to-wheels ethanol production pathway. Reducing these inputs is thus the greatest lever to increase ethanol's net energy ratio and reduce well-to-wheels greenhouse gas emissions [see my full well-to-wheels study more ... a lot more...].

I hope that this process is quickly commercialized. While I am not a huge fan of ethanol from corn, it does offer an incremental improvement over gasoline in terms of fossil energy use and greenhouse gas emissions and does help reduce petroleum consumption. More efficient processes with less environmental impact will make corn ethanol more beneficial.

As mentioned above, one of the best ways to greatly enhance the environmental and fossil energy reduction benefits of corn ethanol would be to eliminate the fossil energy inputs for process heat. This could be done by relying on biomass or biogas instead of coal or natural gas. An integrated biorefinery that utilized both the corn kernels and the rest of the plant - corn stover - to produce both corn-based and cellulose-based ethanol while using the lignin portion of the corn stover as process fuel would have a favorable environmental footprint and offer excellent reductions in fossil energy use, petroleum energy use and greenhouse gas emissions relative to gasoline. An even more integrated process could include an on-site animal feeding operation that used the distillers dried grains or other animal feed co-products from the corn ethanol production process. The resulting animal waste could then be fed to anaerobic digestors to produce biogas that could be used for process heat/steam for the ethanol production plants. Such a facility would likely be able to export a bit of electricity as well.

I hope that in the not-so-distant future, that the ethanol production industry moves in the direction of integrated biorefineries like the one described above. Such facilities could form a sort of industrial ecosystem with one process utilizing the 'waste' from one or more of the other processes. The result would be a much more efficient collection of processes with greatly reduced waste streams and environmental footprints.

[An obvious hat tip to Green Car Congress]