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The Ever-Increasing Efficiency of Ethanol Production
by Kristin Brekke

Ethanol, specifically corn ethanol, often takes heat for not being advanced enough, held to the standard of how future technologies are expected to perform. This point of view misses the new efficiencies that are continually being achieved by America’s ethanol industry, both through increases in ethanol yield per bushel and decreases in energy inputs per gallon.

The production of corn ethanol is a dynamic industry, always evolving and advancing. It’s not standing still, and the numbers prove it.

Data from the U.S. Department of Energy confirms this. A study by DOE’s Argonne National Laboratory comparing data from a 2001 U.S. Department of Agriculture report to a 2007 Renewable Fuels Association survey found significant new efficiencies across a number of categories during that time period – and the trend continues. “Analysis of the Efficiency of the U.S. Ethanol Industry,” authored by May Wu in Argonne’s Center for Transportation Research, found increasing yields and lower energy inputs across both dry mill and wet mill ethanol plants.

And these numbers are backed by real-world examples of how America’s ethanol producers are continually striving to make the good even better.

Today’s ethanol requires less electricity

The Argonne analysis found that modern ethanol plants are using less electricity in the production process than the industry had in the past. From the 2001 report, grid electricity use decreased by 15.7 percent in dry mill ethanol plants. Electricity usage there averaged 0.70 kilowatt hours per gallon of ethanol.

Looking to a combined heat and power (CHP) system is one way ethanol producers can gain efficiency in this area. Generating electric power right at the ethanol plant and making use of the electricity generation’s waste heat can boost overall efficiency from a typical 49 percent to 75 percent, according to the U.S. Environmental Protection Agency.

In a CHP system, a gas turbine electric generator is placed in service with a waste heat boiler. Natural gas produces steam to power the turbine, which provides electricity for the ethanol plant. The turbine exhaust is then used in the waste heat boiler to generate steam to run the ethanol process.

East Kansas Agri-Energy LLC, a 35 million gallon per year (mgy) ethanol plant in Garnett, Kansas, is one producer using a similar technology. The plant’s steam turbine generates about a half-megawatt of electricity, providing approximately one-third of the power needed at the ethanol plant. General Manager Steve Gardner says this equals a 30 percent savings on their electric bill each month.

Last year, the plant received an Energy Star award from the EPA for reducing its energy consumption and greenhouse gas emissions. Its use of CHP reduces carbon dioxide emissions by an estimated 14,500 tons per year, the equivalent of removing the annual emissions of 2,400 cars or planting 3,000 acres of forest, according to EPA.

Wet distillers grain vs. dry cuts energy consumption

Looking to the back end of the ethanol process can also offer some energy – and cost – savings to the producer. The distillers grain co-product can be dried for shipment or sold wet, depending upon the local market area and the ability to secure consistent, nearby customers that can utilize the wet distillers grain.

The 2007 Argonne report found that more ethanol producers, where possible, are cutting out the energy-intensive drying process and selling the distillers grain wet. More than one-third, 37 percent, of the distillers grain reported was sold wet instead of being dried.

Front Range Energy company manager Dan Sanders, Jr. estimates that marketing the distillers wet can save an ethanol plant about 50 percent on its natural gas costs.

“For a plant our size, 40 million gallon nameplate, that means about 15,000 BTUs per gallon of ethanol produced,” Sanders said.

Front Range Energy delivers its wet distillers product to cattle feedlots and dairies, usually within a 60 mile radius of the plant which is located in Windsor, Colorado, an hour north of Denver.

While it’s not always possible for ethanol plants to market 100 percent of their distillers grain as a wet product, many try to do as much this way as possible. East Kansas Agri-Energy reports producing a 70/30 or 60/40 ratio of wet distillers to dry, depending on the season, with the demand for wet feed dropping some when the area’s cattle can be on pasture.

General manager Steve Gardner says the cost savings to the plant all depends on the price of natural gas, but “when gas costs three times as much as it does today, as it has in the past, it’s a big savings."

 

Alternative sources reduce fossil fuel consumption at ethanol plants

While natural gas remains the most common power source for U.S. ethanol facilities, some are looking ahead to innovative ways of rolling back fossil fuel use at the plant.

Siouxland Ethanol of Jackson, Nebraska is an example of an ethanol producer tapping an alternative energy source for power. The 50 mgy ethanol plant has entered a partnership with the neighboring L.P. Gill Landfill to use landfill gas in the ethanol production process. The methane gas is created as solid waste decomposes in a landfill.

Gas piped from the L.P. Gill facility, located one mile from the ethanol plant, displaces some of the natural gas needed to fuel the ethanol process. Siouxland general manger Chuck Hofland says the plant is currently getting about 10 percent of its gas needs from the landfill, and the landfill is working toward an increase in the volume available to the ethanol plant.

“It has been a good partnership,” Hofland said. “The more landfill gas we get, the better it is for them and for us – so this is a win-win situation.”

The ethanol plant experiences some cost savings – amount depending on the market price of natural gas – and the landfill can take advantage of carbon credits for making use of the landfill gas in this way.

“This process is a way to be environmentally friendly in addition to producing ethanol, which is environmentally friendly in and of itself,” Hofland added.

An ethanol plant in southeastern South Dakota, POET Biorefining – Chancellor, is employing a similar system through a partnership with the neighboring Sioux Falls Regional Landfill. There the landfill gas fires a wood waste-fuel boiler to offset much of the fossil fuel-based natural gas previously needed at the ethanol plant.

The use of alternative fuel sources like the methane gas, the practice of marketing wet distillers grain, and the reduction of grid electricity use all add up to significant new efficiencies in U.S. ethanol production. The Argonne report finds that total energy use in the ethanol production process – both fossil fuel and electricity – is down from 2001 by 7.2 percent in wet mill ethanol plants and down by 21.8 percent in dry mills.

In energy input terms, ethanol production in 2001 required on average 39,719 BTUs per gallon, but by 2007, the BTU requirements had dropped to 31,070 per gallon. Experts note that the energy required to produce ethanol will continue to decline as process design continues to advance and as existing producers implement cutting-edge energy saving technologies.

“America’s ethanol producers have an excellent track record of improving efficiency by constantly seeking advancements in the production process ,” noted Brian Jennings, Executive Vice President of the American Coalition for Ethanol. “There is a real desire to be as efficient and environmentally friendly as possible in the production of renewable fuel, and they should be given a lot of credit for their efforts to continually evolve the process in reach of new benchmarks.”

Water use per gallon of ethanol trends down

The 2001 study by USDA marked the amount of water used to produce each gallon of ethanol at 4.7 gallons. In the 2007 Argonne report, water use was down to 3.45 gallons per gallon of ethanol. This 26.6 percent reduction of water consumption is a significant achievement in just a few years’ time.

Ethanol’s water consumption is often pointed to in media discussions, but the 3.45 gallons of water used per gallon of ethanol is small when put into context with the production of other common items. A typical Sunday newspaper, for example, requires 150 gallons of water during its production. One pound of chicken takes 11 gallons of water. And the refining of one barrel of oil requires 1,851 gallons of water, or 44 gallons of water per gallon of oil.

Ethanol producer POET notes that within the last year, its network of 26 plants has achieved an average of 3 gallons of water used to produce a gallon of ethanol. POET’s Bingham Lake, Minnesota in particular has begun using a new technology to bring its water consumption even below the 3 gallon level.

General Manager Randy Dittmann says since February the plant has discharged zero wastewater thanks to a new process that reclaims and reuses water. The Bingham Lake plant initiated a capital project for the new system that reclaims wastewater throughout the plant, filters the water to clean it, then reroutes it back to a storage tank for reuse.

“We’re officially now a zero-discharge facility,” Dittmann said.

Previously, a small amount of water had passed through the process and was discharged into the wastewater system at the back end of the plant. Now the only water to leave the ethanol plant is in the form of steam or in the moisture content of the distillers grain.

The zero-liquid discharge technology has helped the ethanol plant achieve a 26 percent reduction in water usage, down to 2.7 gallons of water per gallon of ethanol.

“POET has always been interested in making ethanol more efficiently and improving the process at all the plants,” Dittmann said, noting the cost benefits and environmental benefits that come along with these process improvements. He added that the City of Windom, which is the plant’s main water source, has also been pleased by the startup of this project because it requires less pumping from their wells and eases pressure on their aquifers.

This is the only POET plant currently using the zero-discharge technology, but Dittmann notes others are considering it. It is a technology that can be added to existing ethanol plants.

Ethanol yield per bushel, corn yield per acre are on the rise

These efficiency improvements in the ethanol production process are leading to higher yields at the plant.

The 2001 USDA data showed an average yield of 2.64 gallons of ethanol per bushel of corn. The Argonne report found an increase in the average yield of 6.4 percent, up to 2.81 gallons per bushel. The survey’s highest reported yield was 2.96 gallons per bushel. Data from wet mill plants also showed an increase, up 2.4 percent to 2.74 gallons per bushel.

At the same time that ethanol yields are increasing, so are those for its predominant feedstock – corn. Improvements in crop genetics and in agronomic management practices are allowing corn yields per acre of American farmland to steadily increase.

Data from the National Corn Growers Association shows that America’s farmers grow five times as much corn today as they did in the 1930s – on 20 percent less land. In 1931 the national average yield was 24 bushels per acre, while it has reached 150 bushels per acre today. And the USDA expects the average yield per acre to double over the next 25 years.

While yields are popping, inputs are trending downward. Over the last 20 years, significant improvements have been made across several different categories:

· a 37% decrease in the amount of land to produce one bushel of corn

· a 69% decrease in soil loss per bushel

· a 27% decrease in irrigation water use per bushel

· a 37% decrease in net energy used to produce one bushel

· a 30% decrease in emissions per bushel

With these successes in hand, it will be interesting to see what America’s ethanol producers and corn producers can do with new technologies in the upcoming years.

© American Coalition for Ethanol, all rights reserved.
The American Coalition for Ethanol publishes Ethanol Today magazine each month to cover the biofuels industryís hot topics, including cellulosic ethanol, E85, corn ethanol, food versus fuel, ethanolís carbon footprint, E10, E15, and mid-range ethanol blends.
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