Ethanol Industry Snapshot

The results of a 2012 corn-ethanol survey reveal progress in yield, energy and water use.
By Chris Hanson | May 15, 2013

To capture an image of where the ethanol industry is going, it is imperative to understand where it has been. In the past five years, the industry persevered through an economic bust, maintained vigilance in its recovery and steeled itself against tight margins with greater efficiencies and valuable coproducts. To learn how the industry is currently faring, researcher Steffen Mueller with the Energy Resources Center at the University of Illinois-Chicago and John Kwik, president of Dominion Energy Services, surveyed ethanol producers to gauge the industry progress in reducing the energy and environmental footprint of corn-ethanol production.

The 2012 corn-ethanol survey was sponsored by the National Corn Growers Association and the Illinois Corn Marketing Board. Additional support came from the Renewable Fuels Association, Growth Energy member plants and the Nebraska Ethanol Board. Out of 162 plants operating in 2012, ranging from 30 to 111 MMgy in production capacity, 84 responded to the survey. The report notes that plants smaller than 30 MMgy and those processing mixed feedstocks were excluded from the analysis.

Historical Comparison
Since the last survey reported by Mueller in 2008, corn-ethanol plants have incrementally improved performance in thermal energy application, water usage and ethanol yield. The study shows that modern energy and processing technologies have reduced the energy footprint of the process, including sophisticated heat integration, combined heat and power (CHP) technologies, variable frequency drives, advance grinding technologies, various combinations of front- and back-end oil separation, and innovative ethanol and distillers dried grains (DDG) recovery.

The 2012 survey shows that ethanol yield has increased 1.43 percent to 2.82 gallons of undenatured anhydrous ethanol per bushel of corn. The progress in ethanol production can be credited to innovations being adopted across the industry despite economic downturns, Mueller says. Through plant retrofits, the producers were able to increase ethanol yields on a per-bushel basis and utilize electricity and thermal energy more efficiently. New technologies in corn production, such as slow-release fertilizers and sophisticated corn hybrids and machinery, have also reduced the overall energy and environmental footprint of the corn ethanol industry. “What the survey shows is that the ethanol industry is still very dynamic,” he says. “Despite economic downturns, the industry has increased yield while simultaneously reducing overall energy consumption at the plant level.”

According to the 2008 report, the average plant utilized 26,206 Btu of thermal energy per gallon produced. The latest findings indicate an 8.95 percent decrease to an average of 23,862 Btu per gallon. Mueller says this figure represents a snapshot across all ethanol plant technologies, coproduct drying practices and geographic locations. To put it in perspective, a 50 MMgy ethanol plant will save more than 117 billion Btu per year in thermal energy compared to five years ago. The energy efficiency improvement is even more dramatic when compared to a 2001 USDA commissioned survey that showed 36,000 Btu thermal energy was used per gallon produced. 

Not surprisingly, corn oil yield increased significantly. The survey shows an average of 0.53 pounds of separated corn oil is produced per bushel—a nearly fivefold increase from the 0.11 pounds per bushel reported in 2008. It’s also notable that the jump in corn oil production resulted in a 0.5 percent decrease in DDG yield and a 2.7 percent increase in electricity usage.

Water use has declined by 0.74 percent since 2008 to 2.7 gallons of water used per gallon of ethanol. Although less than 1 percent change might not seem a large adjustment, it’s more than a 50 percent reduction of water per gallon of ethanol produced in 2005, as reported by the Minnesota Department of Natural Resources. 

Emerging Technology Summaries
Going beyond the average reported among those returning the survey, the report digs into the impact on ethanol yield and efficiencies for 15 emerging technologies.  Some of the most promising technologies for improved ethanol production, Mueller says, are CHP operations, diversification of corn oil recovery systems, better grinding techniques and carbon dioxide scrubbers.

The report describes two CHP turbine configurations that operate at pressures between 150 and 600 pounds per-square-inch gauge. In these models, a steam turbine generates electricity to offset the power bought from the grid while meeting the plant’s thermal energy requirements for process heat. In some locations, the systems are scaled up to generate electricity as a coproduct sold to a local utility.

Both front- and back-end corn oil recovery methods are summarized in the report. The Brix oil separation process for front-end oil recovery increases oil yield from 0.4 to 0.48 pounds per bushel, but at the added cost of increased electrical usage of 0.02 kilowatt (kW) per gallon of ethanol. Higher recovery rates for corn oil can be achieved by combining the traditional oil recovery process with new technology. As an example from the seven back-end oil recovery technologies briefly reviewed, one hybrid system boosts yield to 1.2 to 1.4 pounds of oil per bushel of corn. The process puts together a front-end oil recovery system with back-end oil technology to increase oil yield.

Carbon dioxide scrubbers are another technology featured within the report. This technology involves installing a new condenser ahead of the CO2 scrubber to remove trapped ethanol and return it to either the beerwell or into the rectification column. By utilizing the newer CO2 scrubber technology, plants report a yield increase of 0.1 gallon of ethanol per bushel. 

Plant Configurations
Besides describing the separate emerging technologies, the report takes a closer look at four plant configurations that all yield more ethanol than the reported average. This section of the report was designed to assist plant owners in determining the direction they would like to take their plant, Kwik explains. The plants serve as models for assessing improvement opportunities.

Two configurations are among the most common, differing only in the treatment of the distillers grains. The first utilizes the traditional corn dry-mill process plus back-end oil extraction and 100 percent DDGS. The best performing facilities in this configuration yield 2.85 undenatured ethanol gallons, extract 0.75 pound of corn oil and produce 13.7 pounds of DDGS on a dry basis from every bushel of corn processed.

The second one is identical to the first, with the exception that half the distillers grains are dried and half are sold wet. Both can attain the same ethanol and corn yields and use the same amount of electricity per gallon. However, the second configuration yields, on a dry basis, 6.85 pounds each of wet and dry distillers per bushel while using 16 percent less thermal energy. The report notes the distillers grains yield is lower than the average in both models due to higher ethanol yields.

The next two configurations described in the report illustrate where the industry is heading, Kwik says. One focuses on the production of multiple coproducts utilizing multiple technologies and yields 2.89 gallons of undenatured ethanol, 3.25 pounds of protein, 0.48 pounds of front-end oil, 0.8 pounds of back-end oil and 9.47 pounds of DDGS per bushel, on a dry basis. These facilities utilize multiple technologies to produce the diverse coproducts. In addition to standard dry milling, the model employs batch fermentation, either high or low temperature cooking, advanced grind technology, front-end and back-end oil recovery with advanced systems and protein recovery. “Because of some of the grinding technology, we enhance the coproducts,” Kwik explains. “You also achieve the benefit of additional ethanol and oil.” He adds this creates a metric for achievable goals that can be used by plant owners in their own revenue calculations and to help with comparative analyses of the different technologies.

Kwik says for producers not ready to handle multiple coproducts, the fourth model demonstrates a more efficient plant that produces the highest ethanol yield with lowest overall thermal requirements of all configurations studied, while still producing DDGS. This model yields 2.85 gallons of ethanol, 0.75 pound oil and 13.7 pounds of DDGS per bushel, on a dry basis, but only uses 19,500 Btu of thermal energy and 0.75 kW of electricity per gallon of ethanol. Although the list of employed tools is not as extensive as the third model, it does utilize batch fermentation, either high or low temperature cooking and back-end oil recovery. Where this model stands apart is that it utilizes a superheated flash dryer to bring DDGS down to 11 to 12 percent moisture. About 85 percent of the thermal energy input is recovered by condensing evaporated vapors in an external heat exchanger and by recycling the latent heat of vaporization back into the process. Condensing vapors from the dryer, however, does require the facility to process the excess condensate that cannot be recycled as backset through anaerobic digestion or waste treatment.

Many factors will influence which direction plants take as they plan for future enhancements, Kwik says, with the most prominent being location and finances. “What you do with your plant is really dependent on your geographic location,” he says. He cites facilities in Iowa and Illinois where the cattle-feeding needs of distillers grains customers limit how much oil they can extract, while others near dairy operations are able to extract more oil without affecting distillers grains value.

Although the report offers milestones and methods to producers wanting to increase their ethanol yield, the biggest challenge might be to secure capital to fund projects. The technology is ahead of the financial stability of the current ethanol market. “We have the technology to make plants more sustainable,” Kwik says. “We just can’t get the capital to implement the technologies even with attractive returns.”

Author: Chris Hanson
Staff Writer, Ethanol Producer Magazine
[email protected]