Ethanol reducing its carbon footprint

by Susan Reidy
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Over the last several years, ethanol plant operators have worked to increase ethanol yields, diversify co-products and improve efficiency with the goal of reducing the renewable fuel’s overall carbon footprint.

Research has shown the efforts have paid off, with ethanol plants reducing the amount of thermal energy and electricity needed to produce one gallon of fuel while at the same time producing more fuel per bushel of corn. New technologies, such as corn fractionation, will improve it even further.

"We know that we’ve demonstrated in the last century in corn and in the last 30 years in corn ethanol that technology advances have given us real reductions in the carbon footprint," said Martha Schlicher, technology lead, Monsanto Bioenergy, during her presentation at the International Fuel Ethanol Workshop in June in St. Louis, Missouri, U.S.

Schlicher said technology is available now, and in the future, that will further decrease ethanol’s GHG emissions equivalent to taking 56 million vehicles off the road. Corn production is also improving with reductions in pesticide, insecticide and fertilizer use. With current yields, 15 billion gallons of ethanol require 14 million acres of corn, after correcting for the fact that animal feed displaces corn and soy acres that no longer need to be grown, she said.

"In the quest for the perfect fuel, we have to remember that fuel ethanol exists today and that it can deliver real and certain GHG reductions today," Schlicher said.


A new report on ethanol’s energy consumption provides hard data supporting ethanol’s efficiency improvements in the last seven years. The study, presented by Steffen Mueller, principal research economist, University of Illinois-Chicago, looked at data from 90 of the 150 dry mill ethanol plants operating in 2008.

Mueller compared the results of his study to one done in 2001, which was the last comprehensive survey of energy consumption.

In seven years time, ethanol plants reduced their thermal energy usage by 28% per gallon to 25,859 Btus and reduced their electricity usage by 32.1% to a total of 0.74 kilowatt hours per gallon. At the same time, the ethanol facilities produced 5.3% more ethanol per bushel (2.64 gallons per bushel). Mueller said the plants used 2.72 gallons of water per anhydrous gallon of ethanol and discharged 0.46 gallons of water per gallon.

Accounting for the wet and dried distillers grains produced at the ethanol facilities further offsets their land use effects. Mueller said researchers examined the corn usage for a 100-milliongallon ethanol plant in Iowa.

The plant used 35 million bushels of corn from within a set radius of the facility, amounting to about 8% of the corn area. But the plant also produced 215,000 tons of distillers grains, which saved 104,000 acres of corn and soybean. Accounting for that credit drops the ethanol plant’s corn usage down to 4% of the total area, Mueller said.

Many facilities also are moving beyond traditional co-products, which further improve their energy consumption. About one-third of plants produce corn oil, mostly from back end deoiling of the DDGS.

For example, producing ethyl lactate, which can be used as an organic solvent, can reduce ethanol’s lifecycle greenhouse gas emissions by 8% to 37%. Adding technology such as controlled flow cavitation, which can increase ethanol yield, can reduce GHG emissions on a lifecycle basis by 2.3% and by 4.9% if it is combined with corn kernel fiber conversion.


As efficient as corn-based ethanol has become, there is a move toward advanced biofuels. What that means and how corn-based ethanol becomes an advanced fuel are questions that must be considered, said Pete Moss, vice-president of marketing, Cereal Process Technologies. According to the rulemaking for the Renewable Fuels Standard 2 (RFS2), released by the U.S. Environmental Protection Agency (EPA) this March, advanced fuels must achieve a 50% GHG emission relative to the lifecycle GHG assigned to gasoline from petroleum. Ethanol plants built after 2007 must achieve a 20% GHG emission reduction, according to the RFS2.

"Currently, corn ethanol plants do not, or can not, reach the 50% reduction target," Moss said.

Ethanol plants can try to reduce GHG by reducing energy consumption with technology, using a different source of energy or using a different type of feedstock, he said.

EPA has identified five possible technologies including: fractionation and deoiling; CHP; membrane separation; raw starch hydrolysis; and back-end deoiling. They also determined GHG emission reductions when the different technologies were used.

A dry mill ethanol plant using natural gas that includes fractionation, CHP, membrane separation, raw starch hydrolysis and produces wet distiller’s grains would achieve a 47% GHG reduction in the best-case scenario and a mean reduction of 36%. In order to reach that 50% threshold, a plant would have to use biomass instead of natural gas. Even then, the best-case reduction is 57%, but the mean reduction is 46%, still under the 50% mark, Moss said.

"EPA uses the mean, not the best, so at 46% you’re still not an advanced ethanol technology unless you can prove to them that you’re different," he said. "If you think you’re plant is at 57% reduction, then you can appeal to them and request a pathway for your plant."

But no matter what an ethanol plant does to reduce its GHG, it can not impact the indirect land use penalty in the RFS2, Moss said. In order for corn ethanol to become an advanced fuel, the international land use assumptions need to be revised.

Moss also said that credit should be given to technologies like corn fractionation that provide additional benefits. Those benefits include creation of food products, creation of high quality feed ingredients, creation of feedstock for cellulosic ethanol and creation of additional renewable fuels (biodiesel from back-end corn oil).

"You can’t get these things from other feedstocks or technologies. This is the fastest way to advanced ethanol," Moss said. "We need to give credit to corn and let fractionation take you there."


Ethanol has been accused of increasing food prices and causing world hunger in the so-called food vs. fuel debate. But in reality, there are ample supplies of corn, and there will be even more as yields increase with technology improvements, said Charles Hurburgh, professor, ag and biosystems engineering, Iowa State University.

In fact, corn-based ethanol has been the growth use for corn for the past 10 years, while other uses have been flat.

"If we don’t allow and encourage corn-based ethanol to meet the 15-billion-gallon mandate and continue to grow, we will have a growing surplus of corn that somebody is going to have to do something with," Hurburgh said. "It doesn’t make good business sense."

Many seed industry analysts predict yield increases of 4 to 6 bushels per acre in the next 10 to 15 years, he said. That would amount to 400 to 500 million new bushels of corn per year, which is equal to eight to 10 ethanol plants.

New infrastructure will be required to support the increase in corn yield, Hurburgh said. He estimates that by 2015, an additional 2,064 grain piles with a storage capacity of 1.5 million bushels will be needed. That number grows to 8,944 storage piles by 2035.

All of this new infrastructure will not be cheap, he said, with storage piles costing roughly $15 billion by 2035, round grain bins costing $39 billion and concrete bins costing $71 billion.

Corn drying will also have to increase to the tune of roughly 500 new grain dryers per year. That number will double if the moisture content of corn goes up 1%, which is not unreasonable, Hurburgh said.

Overall, corn production is increasing much faster than traditional uses can absorb, he said, which will generate huge surpluses beyond anything that’s been experienced before if there is a cap on biofuel demand for corn.

It will be critical that corn-based ethanol production be recognized as an industry with growth potential that has to be realized, Hurburgh said. This will require systems thinking in policy planning that considers all the grains together along with all parts of the system from production to processing.

"The case for corn-based ethanol is very strong, and the negative consequences of the surplus in corn that would arise if we do not match demand with supply have yet to be considered by policymakers and producers alike," Hurburgh said.