Ethanol In Context
Use of corn ethanol has
become a contentious issue. What could be
By Eric Jensen, IWLA Energy Coordinator
Ethanol, specifically corn ethanol, has become quite a contentious issue. We deride its short comings in public debates and highlight every aspect of its production and use that doesn’t achieve our goals of what the fuel of the future should be. Our arguments for and against ethanol often sound as if we’re talking about a wholly isolated topic. But we’re not. We’re talking about fueling vehicles. With the current market and state of technology dominated by liquid fuels, there are just two primary options: gasoline and ethanol. So an anti-ethanol stance is effectively pro-gasoline. Therefore, when we weigh the shortcomings of ethanol, we need to make sure our scale is calibrated to gasoline.
Critics often call out ethanol for its poor “energy balance.” Technically speaking, a fuel’s energy balance is calculated by dividing the usable energy contained in the fuel as a finished product by the energy that was required to produce that fuel. One gallon of ethanol (which contains approximately 76,330 BTUs* of energy) requires about 56,500 BTUs of energy to produce. This result gives corn ethanol an energy balance of 1.35. Another way to think of it might be that we put about 7.5 gallons of ethanol in to get 10 gallons out. It’s a small gain, what with all the growing, harvesting, processing, and distribution involved in production.
But what about gasoline? That takes no small amount of extraction, refining, and distribution to produce. For each gallon of gasoline (which contains approximately 116,090 BTUs of energy), the entire production process uses about 142,800 BTUs. That means that gasoline’s energy balance is about 0.82. In other words, we must put in 12.2 gallons of gasoline to get 10 out. Few people realize that we actually lose energy by producing gasoline. If corn ethanol was simply less of an energy loss than gasoline, it would win by comparison — but ethanol is actually an energy gain.
It is also a common argument to call out ethanol for its lower miles per gallon (MPG) value than gasoline. As indicated, the energy content of a gallon of ethanol (about 76,330 BTUs) is less than gasoline (about 116,090 BTUs) — about 35 percent less. Less energy per gallon means we can perform less work by burning that gallon. However, case studies and personal experiences have not shown a 1 to 1 correlation between the energy content and MPG result of using ethanol. For example, although a fuel mix of 85 percent ethanol (E85) has 29.1 percent less energy than pure gasoline, observed mileage reductions are typically in the range of 15–20 percent. This is due to ethanol’s higher octane rating, which allows more efficient conversion of ethanol’s energy potential into actual miles traveled. And this balance could be even more favorable as vehicle technologies advance to better handle a variety of fuels.
Another point of concern regarding corn ethanol is water consumption. Advances in ethanol production have lowered water use down to around 3 gallons of water per gallon of ethanol produced. On top of this, water used to produce corn (which is dominated by irrigation) adds anywhere from 5 to 300 gallons of water per gallon of ethanol, depending on where in the United States the corn is grown. Gasoline production edges out ethanol by using about 2.5 gallons of water per gallon of gasoline produced. However, with greater reliance on crude oil sources like tar sands, this number will jump to around 6 gallons of water per gallon of gas.
In water use, ethanol initially looks like a loser, particularly when taking into account energy content. However, water used to irrigate crops tends to cycle back around, but water used for tar sands mining gets stored in toxic tailing ponds that require active deterrents to ensure migrating birds don’t land on the water and die. So each fuel’s environmental impact regarding water use is also less cut and dry.
An often noted statistic from the U.S. Department of Agriculture suggests that around 40 percent of the corn produced in the United States is used for ethanol. However, there are caveats to this number that aren’t often highlighted. Corn used for ethanol (yellow corn #2) is not the variety of corn used for human consumption. So it’s too simple to suggest that a bushel of corn used for ethanol directly reduces a bushel for someone to eat. Additionally, if you take into account co-products of the ethanol process, such as animal feed, a more accurate number for ethanol’s take of the U.S. corn crop is closer to 20 percent. By comparison, in 2010, a full 40 percent of the U.S. corn crop went straight to animal feed. Although ethanol is clearly a part of the agriculture market, the demand drivers affecting corn and food prices — which include market speculation that can cause significant price fluctuations — are much more varied.
Gasoline infrastructure is already established, and ethanol is difficult to move through pipelines due to corrosion and other issues. On the other hand, corn ethanol is more renewable than gasoline. But increased demand for corn is a partial driver of global land use changes. Closer to home, corn ethanol raises pressure on issues like the conversion of prairie to farm land. However, gasoline demand increases environmental impacts from drilling, flaring, and spills during transportation. Either way, the Gulf Coast gets hit — dead zones as a result of excess fertilizer use on farms or massive oil spills as a result of our demand for crude sources. Clearly, the list of faults when comparing corn ethanol and gasoline can grow rapidly if you’re being thorough.
When all is said and done, it’s important to balance our criticisms with a focus on our goal: Improved transportation fuels. Every point we make has to account for a frame of reference, and it really begs for complaints against corn ethanol to be a bit more measured.
This article might suggest that I’m proethanol. Actually, I’m pro-better-fuels. The future of gasoline is expanded tar sands extraction or deep water drilling, negligible improvements in refining, expanded pipelines over vital aquifers, and long-buried pollutants released into our atmosphere.
In comparison, the future for ethanol is not nearly as dreary. Ethanol plants that use coal for heat are converting to natural gas, while others are integrating biomass-based energy into their systems. The industry as a whole is also advancing — producing more ethanol using less energy, less water, and less corn per gallon. As corn ethanol improves, better and more beneficial biofuels are coming along for the ride, including cellulosic ethanol — fuel produced from other crops and non-food plant materials. The infrastructure used to distribute corn ethanol can do the same for fuels created from more sustainable feedstocks.
Last but not least, it’s important to note the changing playing field. Nearly every major auto manufacturer has or is in the process of introducing an electric vehicle. And natural gas, hydrogen, and other fuel opportunities are being explored. Although not every new option will be an improvement, we need to judge each fuel in the context of competing alternatives to understand its benefits. I’d rather not support a step backward when our new footing puts us ready to leap forward.
— Eric Jensen is the Energy Coordinator for the Izaak Walton League’s Midwest office in St. Paul, Minnesota. He holds a degree in Chemical Engineering from the University of Wisconsin-Madison.
* A BTU or British thermal unit is a common unit of energy approximately equivalent to the amount of heat needed to raise the temperature of a pound of water by 1 degree Fahrenheit.