keywords: wind power, wind turbines, corn ethanol, ERoEI
If a farmer has 1,000 acres of land, and he/she planted it with corn for making ethanol and erected wind turbines for generating electricity, how much energy will the farmer produce and what are the economics?
Wind Power
A typical wind farm will have about 15 wind turbines per 1,00o acres. Each wind turbine will generate about 500 kW of power (assuming 33% capacity factor). Electricity retails at about 12¢ per kW hour. So 1,000 acres will produce 15 x 500 x .12 = $900 of electricity per hour, which equates to about $8,000,000 per year, representing about 224 trillion BTUs of energy.
Corn Ethanol Power
A typical 1,000 acre corn farm will produce about 7,500 pounds of corn, yielding about 340,000 gallons of ethanol. Ethanol retails at about $1.80 per gallon. So 1,000 acres will produce 340,000 x 1.8 = $612,000 per year, representing about 26 billion BTUs of energy.
Energy Returned on Energy Invested
It takes energy to produce energy. The Energy Returned on Energy Invested (ERoEI) for wind turbines is an impressive, state of the art wind turbines are providing ERoEI of over 50:1.
It takes a lot of energy to produce corn ethanol, which yields a far lower ERoEI of between .8 and 1.65 (see Ethanol’s Energy Return on Investment: A Survey of the Literature 1990-Present by Roel Hammerschlag).
Side-effects of Wind Power and Corn Ethanol Production
Wind turbines are often perceived as an eyesore, marring the land with imposing manmade structures. Flying creatures such as hawks and bats are often killed as they pass through the turbine blades. Wind turbines are noisy, and are best located in rural areas, or at sea. Wind power needs to be located near power transmission resources, it that infrastructure will need to be built.
Corn ethanol yields just a bit more energy than it takes to produce it. It takes about 1,700 gallons of water to produce each gallon of corn ethanol. Corn used for ethanol production is corn not used for food production. As food corn supply is reduced, corn-based food prices rise.
Summary
Given 1,000 acres of land, planted with corn and a typical density of wind turbines, the table below summarizes the annual economic and energy value of corn ethanol fuel and wind turbine electricity.
| Wind Power | Corn Ethanol | |
| Retail Value | $8,000,000 | $612,000 |
| Energy Yield | 224 trillion BTUs | 26 billion BTUs |
| ERoEI | 50:1 | 1.5:1 |
Ade says:
Question: How much energy does it take to build, transport, and install 15 turbines, with the associated cabling, switch gear, control systems? Not forgetting the concrete (which emits CO2 when curing) required to hold the turbines in place. Also, how much energy does it cost each year for typical on-going maintenance, and how long will a turbine typically last before it requires total (or majority) replacement?
I don’t know the answer, but I’m guessing it’s “a lot”.
Now compare that to the installation costs of the corn (1 man in a tractor wandering around his fields for a few days); plus, of course, another tractor in autumn to harvest it, and the cost of a bio-fuel production plant (1000 acres will only require a little one).
Now work it out over the lifetime of a turbine. It’s my estimation that the corn output will look a lot healthier if the _total_ picture is taken into account.
Jay Kimball says:
Hi Ade,
Thanks for your comment.
The ERoEI figure considers the life time and totality of the product, whether it is a turbine, corn ethanol, oil, hydro, etc. So all the things you bring up were considered.
There are some very comprehensive studies out there. Google on “ERoEI” and you will find some interesting reading. You can go through a similar search for CO2 related to corn ethanol and wind. Also worth checking out – amount of water consumed, land displaced from food production, etc.
mus302 says:
Your math in the ethanol section seems to be a bit off. Surely you don’t think that an acre of corn only yields 7.5 pounds of corn. Oops.
The total yield of 340,000 gallons of ethanol for 1,000 acres seems a bit low. That equates to 340 gallons of ethanol per acre.
Last year the corn yield was about 165 bushels per acre. This year the yield is expected to be lower at around 155 bushels per acre.
The USDA released a report in June on the latest survey of ethanol plants through 2008 that shows ethanol yield to be at 2.76 gallons from each bushel of corn. Multiply that number times 155 and you get around 428 gallons of ethanol from each acre of land.
You would also get about 2,635 pounds of distillers dried grains for each acre left over after ethanol production. Small point but it too is a source of income that your analysis fails to account for.
It should also be noted that most of that 1,700 gallons of water for each gallon of ethanol produced would be the rain that fell on the corn field while the corn was growing.
The USDA report I mentioned can be found at the following address. http://www.usda.gov/oce/reports/energy/2008Ethanol_June_final.pdf
Jay Kimball says:
Hi mus302. Thanks for your thoughtful reply.
Not 7.5 pounds – 7,500 pounds of corn is produced per acre. See above – I think we are in agreement. So your numbers, and mine, on the bushels/pounds of corn per acre are essentially the same.
Regarding ethanol yield per pound of corn, there are a variety of sources that show a range of gallons per pound of corn. We are both in that range. And I am happy to use the Department of Agriculture numbers. Using their numbers, we get a gross retail value of $770,000 per year for corn ethanol. About 10% of what wind power would produce.
And when you burn that ethanol, it’s gone. When you manufacture the wind turbine, on the other hand, it’s still there, year after year, generating energy, with an ERoEi about 20 times higher than ethanol.
And regarding your comments on water, corn is watered both from above and from ground water. Either way, water is increasingly precious. For more on that, see:
http://8020vision.com/2010/06/27/water-scarcity-in-the-us/
In addition, as we dig in to the secondary aspects of corn production, things like fertilizer needs, nitrogen run-off pollution, etc. are factors to consider.
I was in a meeting last week with congressman Jeff Morris, talking about energy plans for the state, and though we grow corn here, and we have wind, wind power has been the focus of incentives and investments. There is a real commitment to building up renewables and avoiding carbon-based energy sources. And from a jobs perspective, there is a similar commitment to incentivizing cleantech jobs in the state – especially wind and solar technology.
By the way, one of the common wind power issues raised by opponents of wind power is the intermittence of the wind. For an example of the innovations going on to even out wind power production, see:
http://8020vision.com/2010/08/13/using-water-heaters-to-store-excess-wind-energy/
aligatorhardt says:
That 1000 acres could hold a lot more than 15 turbines, and turbines are available up to 5MW each. It sounds like wind energy is a proven money maker.
aligatorhardt says:
The total picture has just been stated. Wind 50 to 1. value in to value out. Ethanol1.5 to 1 or less. ONe man wandering around a field a few days accomplishes nothing. There is far more to ethanol production than just planting some seeds. Wind turbines typically last 25 years with minimal maintenance. When turbines are replaced the foundation and the tower is often reused. Farming can continue around the turbines as larger units have plenty of clearance from the blades. A landowner could make more money off the land by hosting wind turbines than farming could produce.
Grover Lembeck says:
Corn Ethanol is a horrible way to go, but homemade ethanol from available feedstock- now you’re talking! I would primarily like to point out, however, that there is no such thing as ethanol from wood- there’s methanol, with it’s lower energy density (.5 compared to ethanols .75, gasoline being at 1), but there’s nothing you could, say, drink without dying.
That said, corn is an awful feedstock when it comes to gallons produced per acre, and the amount of processing that must be used. In short, the way ethanol is produced could be changed for a huge increase in the EROEI, but that would require decentralizing production, and THAT would lead to fewer profits for Monsanto and AGM.
Mthom3050 says:
Wind and Solar. Bah! In a free market, these pie-in-the-sky dreamcatchers wouldn’t last a day.
jaykimball says:
In a free market, coal and oil couldn’t compete, if you removed their billions in subsidies and tax credits, and made the fossil fuel companies pay the actual costs to the commonwealth, estimated to be between $40 and $90 per ton of CO2. Time to let the free market work for an established industry like coal/oil. If the can’t survive without their subsidies and an honest accounting of costs, perhaps it is time to let them go the way of the dinosaurs and let the new improved cleaner technologies rise.
fireofenergy says:
The graph is misleading because the EROEI for PV is at most, 10