Ethanol as Fuel

Not to start a debate. It seems to be a factual question:

Can corn-produced ethanol provide more energy that went into producing it?

It seems a straightforward question, but an easy answer is hard to figure. If farmers did not get corn subsidies, if the gasoline market were undistorted, if the tax system did not tilt in the favor of farmers, would ethanol be a reasonable substitute or supplement for gasoline?

The answer is NO. If you add up the following energy inputs:
-energy used to make fertilizer
-energy used to grow and transport the corn
-energy used to convert the corn starches to sugars
-energy used to distill the fermented corn sugra solution into alcohol

You wind up with a net loss. the increase of production (of corn-based ehtnaol0 will make the oil consumption INCREASE, not decrease. and finally: ethanol yields only about 70% of the energy of gasoline (per volume). the whole corn-ethanol stupidity represents the triumph of the farm lobby over common sense. It makes as much sense as paying unemployed people to dig holes, and then fill them in.

From a physics point of view, of course no fuel can release more energy when you burn it than was used to create it - the laws of thermodynamics forbid it, but there’s no reason why the energy released by burning ethanol must be less than the amount of energy available from the fossil fuels required to produce it - because the energy in the ethanol doesn’t come from the fossil fuels used to produce it, it comes from sunlight that fell on the plants that made the materials from which the ethanol was produced.

Indeed, it’s perfectly possible to make ethanol without using any fossil fuels at all.

In practical terms, though, I think it is true that the production of ethanol is not currently efficient enough to make it worthwhile, but if we’re going to make the comparison between ethanol and petroleum, and we’re going to factor in all the costs of producing ethanol, then it should be compared to all the costs of producing petroleum - including drilling for it, refining it, transporting and storing it, etc. As I understand it, these costs are often overlooked in such calculations.

Also, there’s no reason why ethanol must be made from corn. In fact, other plants are much better suited for ethanol production. A type of grass called switch grass looks pretty promising, and there have been suggestions that certain types of algaes could be used as well.

But off course there is the energy that enters the system from the sun. What we are doing is taking “free” solar energy and making into a form my Volvo can digest.

Making the stuff from sugar cane might make more sense.

Yes, the system has a significant energy input from the sun, which is why it would be fallacious to say that the amount of available energy in the ethanol product could never exceed the input from fossil fuels. Not that anyone has come straight out and said that here or in any recent thread on the topic, but it always feels like someone is just about to say it.

We could farm and harvest the plant material using wood-fuelled steam tractors, process and mix it by mechanical water or wind power, distil it using direct solar energy, distribute it by horse-drawn cart or sailing barge, etc. - and we would be certainly be producing more energy from ethanol than was available from the fossil fuels used (i.e. none of them).

Of course that might not be an economically viable model, but there’s no fundamental reason why ethanol production must make things worse than not doing it at all.

Cecil addressed the subject already: What’s the true story on ethanol? (28-Nov-2003). The upshot is that it seems likely that ethanol production is a net energy loss.

But hold on a second. The real answer is: it depends. Energy input into ethanol production depends on a lot of things: the raw material, the farming methodology, the ethanol processing technique, economies of scale, transportation costs, and so on. There’s a very good thread related to Cecil’s column (Ethanol as Fuel) that presents and discusses a lot of this information (and includes some awful stupidity, too, but you can probably figure out for yourself which is which).

Unfortunately, a lot of the studies in this area are just that: studies. These require assumptions, and reasonable and knowledgable people can disagree on what the “best” assumptions are. From what I’ve seen, it seems that if a refining process with good efficiency is followed, ethanol production can be a net positive. but even in the best case the “energy production efficiency” will never be as high as it currently is for petroleum.

Yesd, but the whole corn-ethanol thing has been sold as a way to reduce oil imports. it doesn’t! what sense does it make to employ people and lose money? the fact is, an increase of corn-based ethanol production will result in MORE oil consumption, not less. from that point of view, its a failure.

That’s a bit of a stretch. Even if you conclude that ethanol production is a net energy loss (which is debatable, but not unreasonable at all), a large part of the energy input is in the distillation and processing phase. The energy input there would be unlikely to come from oil, but rather from coal (or nuclear, or renewables).

The ethanol produced would then be used (presumably) in automobiles instead of gasoline. Thus, the ultimate energy source would be shifted from purely petroleum to some combination that includes coal (or nuclear, or renewables).

Now, you could argue that ethanol production still doesn’t make economic sense, or investment in ethanol production would be better spent on hybrids, or fuel cells, or electric cars, or whatever, but that’s straying rather far afield from the question in the OP, whic was: Can corn-produced ethanol provide more energy that went into producing it?

It is my understanding that the main reason so much ethanol is being produced right now is not to avoid foreign oil importation, but to replace MTBE as required by law. (MTBE, if you care, is an octane booster which was banned over concerns that it was leaching into ground water. I believe that the deadline for replacing it with ethanol was Summer 2006.) I understand that cellulosic ethanol and ethanol produced from municipal waste gasification has the potential to be a net energy source, but not enough of it can be produced to replace gasoline in the US. Here is another thread about it:


By the same standards, is gasoline any better? We ship crude oil half way around the world, refining uses energy, then gas is trucked or piped across the country. Is that more efficient?

I guess it would be, because time and geology have done some of the work concentrating the energy sources together.

So here’s a short and colorful paper (pdf, but small) that covers ethanol production and compares it to gasoline. The upshot is that for every BTU of gasoline delivered to your local gas station, an additional 0.23 BTU of energy had to be expended in recovery, refining, and transport. For every BTU of ethanol delivered to your local gas station, an additional 0.74 BTU of energy had to be expended in farming, production, and transport.

That, unsurprisingly, makes gasoline a more “efficient” form of fuel because it takes less input (from humans) to make gasoline than it does to make ethanol. However, the total energy coming from fossil fuel is less with ethanol, because only 0.74 BTU of fossil fuel is required to make 1 BTU of ethanol, while 1.23 BTU of fossil fuel is required to make 1 BTU of gasoline.

Note also that this paper concludes that it takes less energy input to make ethanol than you get out of the process.

At tis moment strides are being made in this field. To judge the future use of ethanol on todays info is short thinking. I have run into some new technologies that will use the left over from rice plants. It does not have to be food or feed corn. For example.

We have to do whatever it takes to get us off our addiction to middle eastern oil. As soon as the world moves on from fossil fuels and its non-stop dumping of money into corrupt middle eastern governments (many of which fund terrorist orgs) the better the world will be

Not if “whatever it takes” makes the world unlivable. We’d be far better off reducing our oil consumption overall, rather than trying to grow it. There isn’t enough unused arable land in the US to make enough ethanol to replace oil imports, so it would have to come at the expense of growing food. So then you’re left with importing food instead of oil.

We have the resouces, why not use them? While we piddle with windmills, solar panels and food, the Russians claim the reserves at the North Pole. Seems like the world knows what we are trying our best to ignore.

Fine, use them. What then?

While we/you piddle with those things, countries like Denmark and Germany do them seriously and they make up an increasing portion of their generating capacity. Russia != the world.