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New Study: Ethanol Not a Sustainable Path to Petroleum Independence

A new study of CO2 emissions, cropland area requirements, and other environmental consequences of corn- and sugarcane- ethanol production in the US and Brazil concludes that despite the net energy and CO2 benefits offered by the fuel, using ethanol as a full substitute for gasoline is neither sustainable nor environmentally friendly once the ecological footprint values are factored in.

The researchers also concluded, however, that as part of a diverse energy and fuel portfolio of alternatives to petroleum, “ the ethanol option probably should not be wholly disregarded.”

The paper, “Ethanol as Fuel: Energy, Carbon Dioxide Balances, and Ecological Footprint,” is to be published in the July 2005 issue of BioScience, the journal of the American Institute of Biological Sciences (AIBS).

The researchers, Marcelo E. Dias de Oliveira, Burton E. Vaughan, and Edward J. Rykiel, Jr., use the “ecological footprint” concept to frame the requirements for ethanol production from sugarcane, now widespread in Brazil, and from corn, the main feedstock in the United States.

The ecological footprint is an accounting tool based on two fundamental concepts, sustainability and carrying capacity. It allows the estimation of the resource consumption and waste assimilation requirements of a defined human population or economy sector in terms of corresponding productive land area.

Based on their assumptions and analysis, ethanol carries a positive energy balance (i.e., yielding more energy than directly required to produce it). That conclusion will be somewhat contentious on its own, as the academic debate over ethanol continues to volley back and forth over that precise question.


The energy comes with a fairly steep ecological footprint, however, based on extrapolation from modeled vehicles.


In their calculations, the team used a 2001 Ford Taurus flex-fuel vehicle for the US and a 2003 Volkswagen Golf 1.6 for Brazil.

Fuel Consumption of Modeled Cars
 2001 Taurus (US)2003 Golf (Brazil)
 GasolineE85Gasohol (E24)E100
Fuel Consumption11.2 l/100km14.7 l/100km7.16 l/100km9.81 l/100km
Miles per Gallon (US)21 mpg16 mpg32.9 mpg24 mpg

Dias de Oliveira and colleagues then looked at some consequences of moving to greater fuel ethanol use. The results were unfavorable to fuel ethanol in either country. In Brazil, reducing the rate of deforestation seemed likely to be more effective for taking carbon dioxide out of the atmosphere. In the United States, reliance on ethanol to fuel the automobile fleet would require enormous and ultimately unachievable areas of corn agriculture, and the environmental impacts would outweigh its benefits.

However, the ethanol option probably should not be wholly disregarded. The use of a fuel that emits lower levels of pollutants when burned can be important in regions or cities with critical pollution problems. Also, in agricultural situations where biomass residues would otherwise be burned to prepare for the next planting cycle, there would be some advantage in using the residues for alcohol production. However, further research should be done to improve the conversion process.

Considering that, eventually, petroleum may no longer be available in the amounts currently consumed, one must conclude that substitution of alternatives to fossil fuel cannot be done using one option alone. It will prove more prudent to have numerous options (e.g., ethanol, fuel cells, solar energy), each participating with fractional contributions to the overall national and global need for fuel energy. Finally, it is important to notice that no option comes free from significant environmental problems. [Emphasis mine.]

As a corollary to this, we can note that consuming less is better than consuming more—for example, using a plug-in hybrid architecture to reduce the size of the engine required and the fuel consumed.




We are sooo screwed.


Did anybody think that Ethanol was a sustainable path? After all, it's not even clear if ethanol carries a positive energy balance.

Still, we must continue researching ethanol, and maintaining an ethanol infrastructure. Developing choices that will reduce our reliance on foreign oil will help reduce risk in the long term economy, shielding us from supply shocks like the 70s. Unfortunately, at this point, we're even more subject to possible shocks than 30 years ago... so we really need to get on the ball.

John Norris

My guess is they didn't study (still in its infancy) cellulosic ethanol. And didn't I read somewhere (GCC?) that you can convert part of the conventional ethanol production by-products to biodiesel? Both these would improve the numbers. And another thing, isn't Switch Grass multiples of times better for ethanol production than corn?


They didn’t—they just focused on what are currently the major feedstocks in Brazil and the US. (And yes, there’s a process that allows the development of a biodiesel production line along with the ethanol. :-))

The study is not saying:“Don’t do ethanol.” It’s saying not to expect ethanol to be able to be a complete substitute for gasoline, but that as part of a portfolio of solutions, it may be worthwhile.

The key thing is figuring out what portion of the portfolio.

The number will look better if you’re not dedicating crop land to corn production for fuel—i.e., using the cellulosic approach to biomass waste.

The numbers will also look better if we increase the fuel efficiency of the engines and the applications. One of the reasons the US footprint is worse than the Brazilian is simply the extra fuel consumed in the car selected for the modeling.


Was that study done by the Oil companies?

Frankly - in the short term - we should be going whole hog with BioDiesel. We could grow enough Algae around the Salton Sea to supply ALL of our transportation and heating oil needs if we would just make the commitment.

I doubt that will happen though as long as we have a "president" and "vice-president" in the pockets of the Oil companies.


My concern was that if Brazil's success is in question, then where else would ethanol really work? They've got the climate for sugar cane, which is AFAIK the best sugar crop in the history of the planet. They can grow it year-round. They have low labor rates. They probably aren't too demanding on the environmental impact of the crop or its conversion to ethanol. If the summary is correct, that ethanol is not sustainable even in Brazil ... you better look for some big magic(*) to make it work in northern climes, with high labor costs, and an attentive EPA.

* - those future breakthroughs people so often expect, because, you know, they want them.


The key make or break factor in corn based ethanol is the use of irrigation. Corn grown in Louisiana needs almost no irrigation while corn grown in Nebraska often needs irrigation pumped from a deep aquifer which multiplies the energy use.
Another factor is the use of antiquated distilling methods such as throwing away the cooling water instead of using it to cook the mash.
There is a lot of anti-solar propaganda being spread around by oil and coal lobbyists based on experiments that used stupid engineering.


You don't need to make propaganda to damn corn-ethanol as energetically obscene; quotes from some of its proponents do that quite adequately!  More than thirty-three thousand BTU of natural gas to distill a gallon of ethanol... which yields only 75,700 BTU?

Ethanol plants which burn petroleum-derived fuels or natural gas ought to be shut down by law; the only way they should be allowed to operate is if they use solar energy, waste steam from coal-fired plants, or the like.


It might seem pretty discouraging looking at current technologies
without considering existing ethanol technologies that could
increase land area productive considerable along with
dedicated ethanol engines which would increase compression ratios
to reduce considerably the disparity between flexible fuel vehicle
fuel economy that utilize lower compression ratios designed for gasoline.


We better use coal to distil that ethanol - seriously.

Mikhail Capone

Biofuels are really worthwile when they come from what would otherwise be wasted: Corn stalks that would be burned, agro-business waste, waste wood cellulose, etc.

But the monies and efforts put into growing crops specifically for ethanol/biodiesel probably could better be used in conservation efforts.


I watched that presentation today (pointed to by a few people, I think) by Nate Lewis, Argyros Professor and professor of chemistry at Caltech (second one down on this page

He makes what IMO is a common pont among chemists and physicists: that we have lots of fossil fuels ... if we just count coal, and then goes on to make the point that burning (or not burning) coal is greally a global warming and carbon sequestration question.

Now, here is a bit that is very important. He reminds us that burning coal for power will always produce less greenhouse gasses than burning solid biomass, because (important bit) the basic chemistry says so. The stuff in biomass returns less energy per molecule of released CO2 than the stuff in coal. (And of course the reason oil and natural gas are cleaner still on a CO2 basis is again directly tied to their basic chemistry. See the video for details.)

So (as I think I mentioned on WC a while back) a chemist would really prefer coal over solid biomass. Burn that coal (maximizing energy per CO2 released, and trying to capture the emissions) .. and sequester that biomass underground. To repeat the point, the basic chemistry makes solid biomass more suited to sequestration than energy production.


Man that's ugly ... is it still running? Sorry.

sae gozashti

Ethanol, coal, gasoline, biodiesel, etc. Regardless of what fuel we use for combustion, the less we use, the less we need. The less we use, the less we need to make. The less we need to make, the less we need to use. It is full circle. We need to conserve. If a nation that consumes over 25% of the fossil fuel production of the world, cuts its consumption say by 50% in the next 9 years(Time set by JFK for a man on the moon!), then there will be time to diversify our national energy portfolio. Otherwise, more
COx or NOx or not, we may have no alternatives.


As a matter of fact it would be far better to simply bury paper and burn coal then it would be to burn biofuels. Its even better to convert coal to fuel and burn that while buryin paper to sequester carbon then it is to create most biofuels.

Also one very important point traping co2 at the smokestack isnt much more energy intensive then the mess we have coal plants do now. Its actauly very easy and cheap on an industrial scale to compress co2 into a liquid and pipe it. Hell its easyer to do and cheaper then TRANPORTING natural gas as the pressures are lower.


wintermane:  CO2 doesn't liquefy at room temperature without pressures of hundreds of PSI; according to a friend of mine who was a pipeline operator in a previous life, gas pipelines typically operate at a few tens of PSI.

odograph:  I don't think we should burn coal just to distill ethanol.  If we are going to make ethanol, we should take heat from coal that is already being burned and use that instead.  A steam powerplant will take a small efficiency hit from tapping steam at 250° F and 30 PSIA rather than exhausting to a condenser at 90° F and 0.7 PSIA, but the cost of the lost energy at the turbine shaft is tiny compared to the value of the heat that would otherwise have been made by burning gas or propane.

wintermane again:  If what you say about biofuels is true, it would pay even better to use the biofuels to run an energy cycle which sequesters its carbon throughput.  I'm checking out some of the implications now, so watch The Ergosphere.


How can ethanol be a CO2 emitter? All the carbon came out of the atmosphere in the first place, right? The sugar cane or corn absorbed CO2 from the air and emitted O2, using the carbon to build its proteins and such. Then, later, when we burn the plant or its products, we return the carbon to the air. It can't be a net emitter! The carbon being emitted this year was just absorbed last year.

Somebody's confused here!


Yes, you are.

  1. The fuel which plants, cultivates and harvests the ethanol crops is all fossil in the USA.
  2. The fertilizer which makes US corn yields possible is derived from natural gas (and produces N2O emissions too).
  3. The distillation of fuel ethanol is done with propane or natural gas; AFAIK there are no distilleries using either solar energy or spent steam from powerplants which would come at a negligible cost in additional fuel of any type.
There's good reason to shut down the production of corn ethanol in the USA immediately.


A gas pipeline tends to run at around 2000 psi tho it varies with the age of the pipe. The pipes around here run higher then that. The pipe to your home however runs much lower psi.

A few hundred psi is nothing.


Halfin - the basic idea is that we might do better than break-even in certain situations. Sure, the hypothetical farm that grows its own energy would be "carbon neutral" - but perhaps a farm that bought coal, and sequestered large amounts of biomass would be better than carbon neutral. It might be taking CO2 out of the atmosphere over time.

Such things shouldn't be too hard to calculate.

Oh, and the worst case for the farmer would be if he was buying ethanol or biodiesel from a "bad producer" who was burning large amounts of fossil fuel in the process. We get into these crazy situations where someone might burn way too much natural gas to make ethanol - when he could just run his tractor on natural gas.

E-P - Whether ethanol can/should be distilled with waste energy, that just sounds like another place to run the numbers. Let the most efficient plant design win.


Wintermane:  I've seen cross-country pipeline pipe; it's not that heavy.  Even this thread claims pressures in the "few hundred PSI" range, though higher than what I recalled.

odograph:  Let the farmer run his tractor on the methane from the manure digester of the dairy farm or feedlot down the road.

We could get the most efficient plant designs to "win" if we stopped the outrageous subsidies given to ethanol regardless of how small (or negative) its EROEI is.  Until then....


Oil companies may need the coal in some form if natural gas
isnt readily available for liquefying, distilling and refining
the huge reserves of tar oil sands and shale in western North America
and elsewhere. One could support imminent domain or any means necessary
to access the more easily pumped crude oil and natural gas reserves.
Who knows, they may come online in the not to distant future
then shipped around the world. Will the world continue to strive
for additional energy sources to sustain us and bring,
"Oil Sands To the Fore? 28 June 2004 -- Green Car Congress


MH:  The tar sands miners will never need coal.  They are preparing to gasify some of the bitumen to get hydrogen if/when natural gas gets too expensive.


Engineer-Poet: How are they planing to deal with the water issues?


Odd I guess maybe the show I was watching was wrong on the numbers.... are you sure it was psi and not bar? It could be one or both got messed up in psi to bar conversion numbers.

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