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UC Berkeley Study: Corn Ethanol is Better than Gasoline, But Not by A Lot

Scatterplot of Net GHG and Net Energy Value results from the EBAMM model. Note Cellulosic ethanol to the right. Click to enlarge.

A new analysis by researchers at the University of California, Berkeley concludes that the production of ethanol from corn uses less petroleum energy than the production of gasoline. However, they also conclude that the reduction in greenhouse gases derived by using corn ethanol as a fuel is smaller than some thought—between 10% to 15%.

The researchers note that new technologies now in development such as those for the production of cellulosic ethanol promise to make ethanol a truly green fuel with significantly less environmental impact than gasoline.

The UC Berkeley study, published in this issue of Science, deconstructed six separate high-profile—and contradictory—studies of ethanol. They assessed the studies’ assumptions and then reanalyzed each after correcting errors, inconsistencies and outdated information regarding the amount of energy used to grow corn and make ethanol, and the energy output in the form of fuel and corn byproducts.

It is better to use various inputs to grow corn and make ethanol and use that in your cars than it is to use the gasoline and fossil fuels directly. The people who are saying ethanol is bad are just plain wrong.

But it isn’t a huge victory—you wouldn’t go out and rebuild our economy around corn-based ethanol.

—Dan Kammen, co-director of the Berkeley Institute of the Environment and UC Berkeley’s Class of 1935 Distinguished Chair of Energy

The goal of the UC Berkeley analysis was to understand how six studies of fuel ethanol could come to such different conclusions about the overall energy balance in its production and use. Kammen and Alex Farrell of the Energy and Resources Group at UC Berkeley, with their students Rich Plevin, Brian Turner and Andy Jones along with Michael O’Hare, a professor in the Goldman School of Public Policy dissected each study and recreated its analysis in a spreadsheet where they could be compared side-by-side.

The studies reviewed were:

  • Fossil Energy Use in the Manufacture of Corn Ethanol; Dr. Michael S. Graboski, Colorado School of Mines, Prepared for the National Corn Growers Association (2002)

  • The Energy Balance of Corn Ethanol: An Update; Hosein Shapouri, James A. Duffield, and Michael Wang; U.S. Department of Agriculture, Agricultural Economic Report No. 814 (2002)

  • The 2001 Net Energy Balance of Corn Ethanol; Shapouri, H., Duffield, J., Mcaloon, A.J.; Proceedings Of The Conference On Agriculture As A Producer And Consumer Of Energy, Arlington, VA (2004)

  • The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) Model, version 1.6; Michael Wang, Transportation Technology R&D Center, Argonne National Laboratory

  • “Thermodynamics of the Corn-Ethanol Biofuel Cycle”; Patzek, T.W.; Critical Reviews in Plant Sciences 23(6), 519-567 (2004)

  • “Ethanol as Fuel: Energy, Carbon Dioxide Balances, and Ecological Footprint”; Marcelo E. Dias de Oliveira, Burton E. Vaughan, and Edward J. Rykiel, Jr.; BioScience, 55(7), 593 (2005)

  • “Ethanol Production Using Corn, Switchgrass, and Wood; Biodiesel Production Using Soybean and Sunflower”; David Pimentel and Tad W. Patzek; Natural Resource Research, 14(1), 65-76 (2005)

The UC Berkeley team has made its spreadsheet model, the Energy and Resources Group Biofuels Meta Model (EBAMM), available to the public on its Web site.

The team said it found numerous errors, inconsistencies and omissions among the studies, such as not considering the value of co-products of ethanol production—dried distillers grains, corn gluten feed and corn oil—that boost the net energy gain from ethanol production. Other studies overestimated the energy used by farm machinery.

On the other side, some studies ignored the use of crushed limestone on corn fields, which can be a significant energy input because of the need to pulverize the rock. Farrell noted that some numbers needed for the analysis, such as the amount of limestone applied, are just not known reliably. On the other hand, some of the studies used outdated data when more recent numbers were available, making ethanol look worse.

The UC Berkeley team calculated a Net Energy Value (Output energy - Input energy) for corn ethanol of 4.5 MJ/Liter. Cellulosic ethanol fares much better, with a calculated Net Energy Value of 22.8 MJ/L.

Farrell, Kammen and their colleagues considered not only the energy balance of corn ethanol production, but also the effect on the environment through production of greenhouse gases. While corn ethanol came out marginally better than gasoline in terms of greenhouse gas production, Farrell noted that corn production has other negative environmental impacts associated with fertilizer, pesticide and herbicide use. These need to be taken into account when considering the balance between corn ethanol and gasoline, though emerging cellulosic technologies using waste would push the equation more toward ethanol.

Two things are going to push the commercialization of cellulosic technology. One is driving the cost down, which is mainly research and development; the other is that environmental concerns are increasingly entering into commercial calculations about biofuels."

—Alex Farrell

Kammen estimates that ethanol could replace 20% to 30% of fuel usage in this country with little effort in just a few years. In the long term, the United States may be able to match Sweden, which recently committed to an oil-free future based on ethanol from forests and solar energy.

Kammen last year published a paper, also in Science, arguing that even Africa could exploit its biomass to build a biofuel industry that could meet energy needs for the poor and develop a sustainable local fuel supply, a future much better than using fossil fuels.


  • “Ethanol can contribute to energy and environmental goals”; Farrell, A.E., R.J. Plevin, B.T. Turner, A.D. Jones, M. O’Hare, and D. Kammen; Science, 311. 506 - 508 (2006)

  • ERG Biofuel Analysis Meta-Model



Well, that's a big win for Ethanol: it ain't bad.

Seriously. That's what it will hang it's hat on. It ain't bad.

It results in less oil consumed. That aint' bad.
It results in more jobs and money staying US-side. That ain't bad.
It results in less greenhouse gas emissions. That ain't bad.

None of it is amazing, but it ain't bad. Since every little bit helps, a move toward more ethanol would be a positive step, albeit a fairly small one in a long journey.


Please keep in mind that all farm equipment- tractors, etc, could and should be made to run on SOLID biomass ( by stirling engines) which would make the petroleum input less and the energy return better.

Some Guy

Have any studies similair to this been done for bio-diesel?


Assuming the best case of 15% savings, this is equivalent to increasing the gas mileage of a 20mpg car to 23.5 mpg. And I am not sure that this considers any decreases in mileage that may occur from using ethanol.

This is why we need to not be deluded into thinking that we solve the oil and ghg problem by converting to ethanol. It helps a bit but real progress will occur when we significantly increase the average mpg to the entire fleet. GM is emphasizing their efforts in the ethanol area in an attempt to cover up their pathetic progress with respect to their CAFE.


FINALLY, a reputable source has set the record straight!

Considering the 15% reduction in petroleum is essentially the worst case scenario, this seems to be a very viable option to help offset our petroleum consumption in the near future.

We need to do everything to encourage the production of flex-fuel vehicles right now, so that about the time there are enough of them on the road to make an impact, a higher percentage of ethanol will inevitably be coming from the much more efficient cellulosic methods. The market will dictate that even if the government doesn't.

It's not going to solve the problem, but it'll help.

Harvey D

Cellulosic ethanol with 5X Net Energy Value is certanly more interesting than corn/grain ethanol and should be favoured. The 15% net gain with corn ethanol makes it hard to sell. Why use good corn or other edible grains to run our gas/ethanol guzzlers if we can use waste and other less useful stocks? The choice seems to be an easy one to make. Of course, the corn and grain lobbies will put up the usual fight and probably win.

An Engineer

Finally, a study that makes some logical conclusions:
1. Converting food to fuel is at best marginal.
2. Converting waste to fuel is a great solution!

George Bush

So this study shows us that ethanol is worthwhile if we burn it in a automobile...then the next question is how can we do even better. Well the answer to that has been discovered by long time ethanol research Dr. Lanny Schmidt. Call it the last mile on the quest of ethanol...that last mile that turns it into hydrogen.

"Ethanol is easy to transport and, as Schmidt puts it, "relatively nontoxic." It's already burned in car engines, but it would yield nearly three times as much power if its energy were channeled into hydrogen fuel cells instead.

"We can potentially capture 50 percent of the energy stored in sugar by the corn plant, whereas converting the sugar to ethanol and burning the ethanol in a car harvests only 20 percent of the energy in sugar," says Schmidt.

The difference is largely due to the fact that the last thing you would want to do is put water in your gas tank, says Gregg Deluga, a coinventor of the reactor and a scientist who formerly worked in Schmidt's lab. The fermentation reactions that produce ethanol take place in water, and removing every last drop of water from a batch of ethanol takes plenty of energy. But the Schmidt reactor doesn't require that water and ethanol be separated. In fact, the reaction strips hydrogen from molecules of water as well as from ethanol, yielding a hydrogen bonus. "

You can read more about Lanny Schmidt's work here...

My good friend Senator Barak Obama has worked hard to bring this last mile to Chicago...with an ethanol to hydrogen fueling station. The fuel can be transported the same as fuel is today...and then converted efficiently to hydrogen using a process like Dr. Lanny Schmidt describes above.

You can read about the ethanol to hydrogen fuel station here...


Very true, but keep in mind that much like consumers cannot choose between domestic and imported petroleum, they will not be able to choose between corn-based and cellulosic ethanol.

Regardless of the marginal impact of corn ethanol, we should only encourage it. That's the only way consumers are going to buy into this right now. We need this so that flex-fuel vehicles start becoming the norm. The increased demand will necessitate increases in cellusosic ethanol to meet that demand. Corn ethanol just won't do that.

We currently have excess production capacity of corn as a food source, so the corn ethanol isn't really taking anything away at this point.

Changes aren't going to happen overnight, so we need to start the ball rolling now. Most current hybrids only reduce oil consumption about 15%, and that's for less than 1% of the cars on the road right now! Given the limited modifications required to run on 85% ethanol, that could very quickly account for a significant portion of our cars. That doesn't even consider the 10% that nearly every car in America could run on right now.


Regarding the research by Dr. Lanny Schmidt.....

The conversion of ethanol into hydrogen makes a lot of sense. However, wouldn't it make much more sense to place larger-scale fuel cells right at the ethanol factories, and just transport the electricity instead of the hydrogen?

This seems like it could complement Plug-in hybrids very well.....

Dick Cheney

Electricity on the wire must be consumed at the time of production to be usual. Batteries are much to costly to save up energy that way. Ethanol and hydrogen of course can be stored indefintely without giving up any of it's energy. This means you don't have to build your electrical infrastructure to be so enormous to cover the peak demand...and have it go to waste during off peak. This lets you produce the energy and use it independently of production very efficiently. In addition, plug-ins will do little to stop pollution on our highways. Once folks turn on the heaters and the air conditioners while sitting idle in traffic...that battery charge will go quick...leaving the vehicle to run on gasoline for the remainder of the time. During this period it will continue to emit harmful emmissions just as our vehicles do today. With hydrogen vehicles, however, be they hydrogen internal combustion engines, hydrogen hybrids (plug-in or otherwise), or fuel cell vehicles the emmissions will be almost nil.


The problem with corn-based ethanol is that, at least for now, it is more expensive to run your car on ethanol than on gasoline, due to its lower energy density. Increasing fossil fuel prices will presumably also translate into parallel increases in ethanol prices, due to the increased cost of growing, refining and transporting it. It sounds like cellulosic ethanol may be a different matter, but it seems to me that the pure economics of the current ethanol realities will not drive the market to large scale adoption. If I have a flex-fuel car, and it costs me more to drive 100 miles on ethanol than it does to drive on gasoline, I'm going to buy gasoline. The exceptional consumer altruists out there who will pay more for fuel for the sake of a marginal benifit to the planet are too few in number to change this basic economic fact.

The real solutions lie in changing how we use energy to get around, i.e. mass transit, denser housing patterns, bicycles, *much* higher mileage vehicles, etc.


Also keep in mind that the lower energy density can be partially offset by an engine truly optimized to run on ethanol. Existing FFVs only make minor adjustments. Saab's Ecopower concept takes advantage of ethanol's significant higher octane rating. Much higher compression ratios can be used to take advantage of this increased octane, making the engine more efficient. In turn, Saab's concept could be applied to a smaller engine to make the same power as a larger gasoline engine. This would make the overal fuel consumption very close.


"Batteries are much to costly to save up energy that way"

Not sure what types of batteries you are referring to (to treat all equally does not make sense) or what you are benchmarking this against. If it's fuel-cells, I fail to understand your reasoning. Many theoretical ideas need to come to fruition before these are affordable, whereas efficient battery technology is being developed right now. Check out

Also, near-term PHEVs would be most likely charged during off-peak hours. Additionally, electricity is bought wholesale. If this concept is as efficient as you advertise, it will be very competitve from a cost perspective, and thus it would be the fossil fuel plants that might have to cut back on their production. Sounds like a win-win scenario to me.

There is NO WAY that using a liquid, transported primarily by trucks, is a more efficient energy carrier than using our existing electical grid.

Barak Obama

As stated by my esteemed colleage Mr. Cheney, there is no decent means by which to buffer thousands of megawatts of energy within our existing electric infrastructure. A123 Systems will make nice batteries for electric drills for sure...but they will not be buffering thousands of megawatts of energy. If everyone switched to plug-in hybrids there would no doubt need to be an increase in the current electrical infrastructure of at least 25%. That's a heck of a lot of new coal plants, oil plants, and nuclear plants.

Ethanol can be produced, however, even utilizing various forms of intermittent energy like solar and once in the form of ethanol it will stay that way indefinitely rain or shine or whether there is a power outage or whether we are at peak power consumption or not. This allows it to act as a buffer between the act of supplying power for production and the consumption of the resource. This allows supply and demand to be leveled out efficiently, so you don't need to size things based upon the most you might use at any one point in time, but instead by what you would use on average (a much much lower number).

This allows you to utilize your capital resources much more efficiently.

Your very own mother

Did I miss something?

Several comments stated that using ethonal reduced oil consumption by "at best 15%". That's not what this article says. The article stated that "(the) reduction in greenhouse gases derived by using corn ethanol as a fuel is...10% to 15%."


No, you are correct. The author boldly stated, "production of ethanol from corn uses less petroleum energy than the production of gasoline" in his first sentence. However, he implied the GHG benefits were less significant, and quoted that figure of 10-15%

So, for the sake of the argument, I was quoting what I assumed to be the worst case scenario for the petroleum savings.


Mr. Cheney, I think it's becoming painfully obvious that once again, you are speaking on behalf of the big oil companies that have you in their back pockets, as they are better situated to become the power brokers of this new hydrogen infrastructure.

ANY committment to building such will mean a committment to cars that run on hydrogen. This ethanol to hydrogen solution you proposed won't come close to meeting demand, so most of the hydrogen will come from fossil fuel sources in the immediate future.

The point, that you somehow missed, is that PHEVs offer a solution RIGHT NOW. Most likely not the ultimate solution, but one that can nonetheless be significant.

Are you suggesting that our current electrical grid is not equipped to meet fluctuations in power demand? If you average our daily electrical consumption, we have plenty of total capacity to accomodate a significant number of PHEVs. The problem is that there is not enough of a market during these off-peak hours, creating significant surplus production capacity. In the near future, nearly all PHEVs would be charged overnight.

...and the battery technologies SUCH AS the one A123 systems has developed are being developed for automobile applications as well. We are not getting rid of the ICE anytime soon, so we'll have to find a way to make this system more efficient.


Let me be clear though - I'm not knocking this proposal from Dr. Schmidt. I'm saying that if it really is as good as advertised, lets not make it dependent on a market for hydrogen or fuel cells which are farther down the road. Even without PHEVs, we are going to need to add capacity to our electrical grid. It sounds like this could contribute right away. Down the road, if it was determined that the hydrogen could be distributed more efficiently, the production would be ready.


One poster said, "PHEVs offer a solution RIGHT NOW." This is simply not true. The storage technologies are not there, and it requires about a trillion dollars worth of new generation and distribution infrastructure.

Meanwhile, iron phosphate cathode lithium ion batteries are achieving high energy densities (competitive with the best hydrogen storage technologies), low cost (better than hydrogen), fast recharge (around five minutes), and can use existing infrastructure, namely the wall outlet in everyone's home.

And if you want high energy density, use ethanol or gasoline (liquid at room temperature, easy to store, use existing distribution infrastructure) in a solid oxide fuel cell (already in production vehicles, dropping rapidly in manufacturing cost).

How do you propose to overcome these difficulties and competitors?

[q->t to email]

Richard Branson

Right PHEV is not here. What is really here is ethanol to hydrogen and hydrogen internal combustion engines (including hydrogen internal combustion engine hybrids). Lots of folks are working on converting existing Toyota Prius's to run on hydrogen including Energy Conversion Devices and Quantum Technologies among others.

Here's someone doing ethanol to

Tom Toyota

What was that you were saying about converted hydrogen Toyota Prius's?

Here's a few rolling out:

Mary Mazda

Speaking of hydrogen internal combustion...don't forget about that which is also here "now" from Mazda. Mazda has begun to lease the dual fuel capable hydrogen/gasoline RX8 and they have plans by 2008 to introduce a production version of a dual fuel capable hydrogen/gasoline hybrid Premacy mini-van.

"Finally, Mazda continues its push to developing a hydrogen-fueled rotary combustion engine for a mass production vehicle. Imaki affirmed that Mazda will begin leasing its RX-8 RE hydrogen cars (earlier post) starting next spring, a half-year earlier than planned.

Imaki also said that the company intends to offer the Premacy RE hydrogen hybrid concept vehicle, which combines the dual-fuel, hydrogen/gasoline RENESIS rotary engine with a Mazda mild hybrid system (earlier post) as a mass production vehicle within three years"

Here's the story on GCC...

Dolly Madison

Don't forget about my home town friends here in Madison that are able to more directly convert biomass to hydrogen and other alkanes bypassing the ethanol step.


Where is it documented that hydrogen can be stored indefinitely? My understanding is that one of the "challenges" with respect to hydrogen is that, because of its low density, that there will always be leakage regardless of the container.

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