cvitae.org - Is Corn Ethanol "Worth" it?

Is Corn Ethanol "Worth" it?

Wednesday, 15 August 2007

So you think your 10 mpg SUV is green, because it takes ethanol? Latest research indicates that's not so true if your ethanol is made from corn. With current corn ethanol production techniques, the benefit to the environment is roughly 14%, so your 10 mpg SUV is really about 11 mpg. Furthermore, it appears that those engines are not so efficient taking away that 14% edge. You can still be happy, since you just saved the poor American farmer (subsidized at $10 billion annually), as well as the coal and natural gas miners, and improved national security.
	Fig 1. Ethanol conversion rates according to the NCGA http://www.ncga.com]

Ethanol based fuels are a "hot" topic these days. Brazil is extremely successful with the ethanol fuel program based on sugar cane. The US does not want to lag in this area, but, since sugarcane is scarce in the US, corn based ethanol seems to be at the focus. This has gotten the corn industry giddy, considering that corn demand for food remains fairly flat. Corn is not the most efficient source of ethanol, and it is a worthwhile question to ask whether it's a good idea to grow more corn to replace oil.

How clean is corn ethanol?

The main gripe with corn ethanol has been the claim that corn ethanol is energy negative, meaning that it takes more energy to make it than you can get out of it. Furthermore, since the energy inputs to ethanol production are petroleum and coal based, these increase green house emissions. I would think that political value due to self sustainability of corn ethanol is also a significant benefit from a political standpoint. A paper by Farell et. al
in Science [1], discusses the energy balance of corn ethanol and compares several corn ethanol production schemes based on their energy utilization and green house emission. They find that the current ethanol production requires approximately 0.8 MJ of inputs per MJ of corn ethanol output with 0.05 MJ from petroleum and the rest from natural gas and coal. The current ethanol corn production would result is approximately 14 % less green house emissions compared to ethanol. The findings of Farell et. al. mirror those of other authors cited in the work and disagree with two results, which attributed negative energy to corn ethanol. The positive value of current corn ethanol production is not very large. The most important benefit is that petroleum is not a significant component of the ethanol production process with the majority of energy coming from coal and natural gas. Cellulosic ethanol, as analyzed by the authors seems to be the best bet for energy production with a 6 fold increase in energy production over current ethanol and ~ 90 % lower green house emissions than gasoline.

[1]

FarrellEthanolScience012706.pdf

How much does corn ethanol cost?

According to the National Corn Growers Association [http://www.ncga.com], the efficiency of corn ethanol extraction is about 3 galons/bushel, as you can see in Fig 1. One bushel of corn is : 56 lb ≈ 25.401 kg according to wikipedia. And a bushel of corn is expected to sell for approximately $3-$4 [CNN] with US production of approximately 12 billion bushels expected in 2007. With an annual subsidy of approximately 10 billion [see Fig 2], corn is ~ 25% subsidized - so it is effectively $5 for a bushel, or $5 for 3 gallons of corn ethanol. This is indeed cheaper than gas, if we don't consider distribution costs and costs associated with the actual production of ethanol from the corn. The white house also pledged to potentially drive down the cost of ethanol with more corn subsidies.

Can your car run on ethanol?

According to this article on wikipedia 10% Ethanol in gasoline mixtures are OK for most cars today and would only result in a 2% drop in efficiency. Flexible Fuel Vehicles (those taking 10%) would take a much larger hit 15-30% if E-85 is used in them.