Rising Nucleotides

Ethanol Won't Save the World

Having received a request for more science (and, indeed, for new material of any sort), I decided to go to CNN.com and see what was new. And the first thing I found was:

MINNEAPOLIS, Minnesota (AP) -- Researchers say they have produced hydrogen from ethanol in a prototype reactor small enough and efficient enough to heat small homes and power cars.

Now, I applaud their ingenuity, and I favor hydrogen as the energy carrier molecule of the future. But... extracting hydrogen from ethanol as a source of energy is so utterly wrongheaded...

Wanting evidence to back up this article (which I had planned to be a righteously indignant slam of ethanol energy), I performed a quick Google search for ethanol corn energy production. I was quickly reassured that I was not the first person to look at the matter with a critical eye. By the end of the investigation, however, I had found that ethanol energy is more complicated than it seems.

Firstly, let's lay some groundwork. Ethanol-- a.k.a. grain alcohol, a.k.a. drinking alcohol-- is commonly produced from sugary or starchy feedstocks, via fermentation by yeast. The molecule is made up of two carbon, six hydrogen, and one oxygen atoms. That oxygen is related to why ethanol contains less energy per unit volume than gasoline, but also has a higher octane rating, and results in less carbon monoxide when burned. Ethanol is corrosive, and has an affinity for water, both of which make it more troublesome in gasoline blends than the competing oxygenate MTBE. (Though MTBE has political problems.)

Ethanol is an example of biomass energy, meaning that the fuel comes from living things. Modern living things, that is-- fossil fuels came from biomass originally, but their ancient origin sets them apart. Biomass energy seems like a convenient way to harness the power of the sun cleanly and efficiently, but the reality isn't as tidy-- and ethanol is the worst offender.

Every discussion of this issue seems to bring up Dr. David Pimentel, of Cornell University, who claimed that "about 70 percent more energy is required to produce ethanol than the energy that actually is in ethanol." He is rather quotable, what with statements like "Abusing our precious croplands to grow corn for an energy-inefficient process that yields low-grade automobile fuel amounts to unsustainable, subsidized food burning." (Press release here.)

The National Corn Growers Association fired back, insisting that ethanol energy was a net positive by 29%. Apparently, Dr. Pimentel had used some outdated numbers. A forgivable error, since his work with the Department of Energy was two decades ago-- but a fairly stupid one, as errors go. Dr. Pimentel's newer paper puts ethanol at a net energy loss of 29%. Naturally, most of that input energy comes from fossil fuels-- which would then seem to make ethanol useless... more on that later.

No matter which numbers you use, it clearly takes a lot of energy to produce ethanol-- and that's completely ignoring the energy input from sunlight. Why is that? Well, I'm glad you asked.

Commercial ethanol fermentation currently requires high-quality starchy feedstocks, and that means grain (the overwhleming majority comes from corn). Growing corn involves the use of large amounts of nitrogen fertilizer. Current forms of nitrogen fertilizer require a disturbing amount natural gas to produce. There are other energy costs in corn production, such as equipment fuel, but fertilizer is the big one.

There are many energy costs at the ethanol plant as well, but there is again a single large one-- that being heat for distillation, which is generally supplied by coal. Separating ethanol from water is what we scientists call "a pain." Three distillations isn't enough, in fact, and you have to resort to other tricks to get most of the remaining 5% water out.

Ethanol from corn will never be a stunningly efficient energy carrier molecule. There is a catch to all of the doom and gloom, though. Note that most of the input energy is from natural gas and coal-- both of which are extracted in large quantities in the United States. Ethanol is actually a way of transforming US fossil fuels into a liquid fuel for vehicles. It does, in fact, decrease US dependence on foreign oil-- just by a small amount.

But at what cost? Growing corn requires intensive agriculture, which has its own environmental concerns. As a former farmer, I won't tell you that growing corn is horrible, but that doesn't mean I think we should go out of our way to grow it for dubious purposes. Ethanol production involves burning coal (or natural gas, or #6 oil). Environmentalists, as a group, hate both agricultural runoff and burning coal. Thus, logically, environmentalists should vigorously oppose ethanol from corn.

It is often said that the US government's subsidization of ethanol is at least good for farmers, since it raises the price of corn. This is misleading. True, it does raise the price of corn-- but that's bad for farmers who use corn, which is nearly every farmer with animals. Comsumers of food pay higher prices either way. You're being taxed for the honor of paying more for corn-shelled, meat-filled tacos. Feel free to complain to your US senator, or to the infamous Archer Daniels Midland Corporation. Cecil Adams certainly gave ADM the treatment when he talked about ethanol.

Why do I keep specifying ethanol from corn? Well, that's because nice, starchy corn isn't the only possible feedstock for ethanol. But that's a topic for another day-- especially since such other sources are not yet ready to compete.

Speaking of alternative fuels (tm) to be discussed in my next such article, it turns out that today is National Biodiesel Day. It's Rudolf Diesel's birthday, you see. Of course, I seem to recall that Rudolf's original engine ran on coal dust, but that's just splitting hairs. =) Come on, smile.

Posted by Mitch at March 18, 2004 11:56 PM
You can find this entry in: Environment , Technology