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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 They assessed the studies’ assumptions and then reanalyzed each after correcting errors, inconsistencies and outdated information regarding the amount of energy used to grow corn and make ethanol, and the energy output in the form of fuel and corn byproducts.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



These studies seem to have forgotten a pilot technology mentioned right here in GCC. A nebraska facility will power an ethanol plant with sewage methane, derived from feedlot manure. Undigested sewage is nitrogen rich, qualifying as substitute corn fertilizer. No petroleum used at all. Since feedlot methane is essentially a stranded fuel evaporating into the air, you can consider this a net increase of fuel stock.

Also: Ethanol and the hydrogen economy are NOT really two diffent things. You can heat ethanol or methanol anaerobically to release hydrogen, if you needed pure hydrogen badly enough.

Dolly Madison

Oh hydrogen contained in a sealed gaseous vessel does not leak. That is the fodder of those shilling out a propaganda campaign. You should question very deeply the source where you heard that lie. Hydrogen is produced in massive quantities all over the world today. 45 billion kilograms or enough to fuel 250 million fuel cell vehicles (per the Air Products web site).

Like any needs to be contained in an appropriate storage vessel. Gaseous hydrogen storage vessel simply do not leak.

Dolly Madison

Nice to see GCC has weighed in showing the advantage of Virent Technologies biomass to hydrogen conversion techique. This is hardly to discount the validity of ethanol to hydrogen, but it does show that APR is even more efficient.

The key to understanding why even ethanol to hydrogen is still a good idea is realizing that hydrogen is not the end game. They game is to achieive miles on the road. A fuel cell vehicle running on hydrogen can achieve those miles on the road 2-3 times more efficiently than a vehicle running on ethanol internal combustion. Not to mention it does so while emitting zero green house gases and most importantly zero harmful pollutants.

Here's the new GCC post on Virent...



Those technologies relying on offal or waste are functional and efficient -- but in general don't scale. That doesn't mean that they shouldn't be persued, but that their costs don't accurately "speak for" the costs necessary to meet a wide-scale demand.


My mistake... I was under the impression above that H in PHEV was related to hydrogen, but it's plug-in hybrid electric vehicle. With the batteries I mentioned on their way into production, PHEVs will be kicking hydrogen's butt in the next 2-3 years, with the last nails going in that coffin when the plunging costs of solid oxide fuel cells make their efficiency gains vs. ICEs worth their higher cost.

But that's what I said above. :-)

[q->t to email]


Adam, glad you finally agreed with me. This board can be brutal at times!

I find it odd that so many people are supporting the hydrogen ICE concept, to go along with this new sugars-to-hydrogen proposal. Perhaps people didn't read down to the paragraph about the 80 mile range! All the efficiency in that process is gained in production, not distribution. If we even try to sell people on that concept, they'll never buy it. 80 mile range....

Forcing hydrogen ICE's to the market just to get this sugars-to-hydrogen process to the market is not wise at all. Instead, as I proposed earlier, bring it to the market right now, but turn it into electricity using existing technology (and eventually, fuel cells). There is quite a market for electricity right now. WHEN there is a market for the hydrogen, some or all of these plants could just start distributing the hydrogen. It's as simple as that.

Some guy was knocking the inability to store large amounts of electricity. A couple things - one, there are plenty of generating plants that can vary their output, to balance out the overall grid (and conveniently, most of those are the dirtier fossil-fuel driven ones). Second, people's CARS (PHEVs) collectively serve as additional electrical energy storage. Third, how the hell do we start stockpiling these excess reserves of hydrogen? For that matter, how much refined gasoline does this person think we now have stockpiled? (PLEASE don't get gasoline confused with our Strategic Petroleum Reserve)


For example, here is a realistic near term solution we could strive for:

1. Plug-in Diesel hybrids that can run on any percentage of biodiesel.
2. Finding more efficient ways to produce biodiesel. This can be accomplished through more efficient farming methods and/or by finding a source with higher yields than soybeans (and many exist that do)
3. Biodiesel waste, the cellulose from the soybeans (or whatever stock is used for the biodiesel) is used for this sugars-to-hydrogen process, and turned into electricity to supplement the grid.
4. Applying the Fischer-Tropsch process to turn sewage and animal waste into diesel.
5. Increased production of tradtional diesel to make better use of the petroleum we have.
6. Additional sugars-to-hydrogen plants using other sorts of cellulose. Primarliy waste, but supplemented by surplus food-source production.
7. Ramping up renewable energy production such as wind (which already is as cheap as coal), solor, geothermal, and others (such as the new hydro proposals that capture wave energy or run underwater turbines to take advantage of currents) to supplement peak energy demands that the PHEVs will hopefully result in over time.

What are we left with after 10 years of investment? Plenty of vehicles on the road that are primarily driven by electric components (drivetrain and accessories). These would be MUCH easier to convert into fuel-cell vehicles if advances were made there (as most components could be reused, and from above, these suger-to-hydrogen plants would be in place). If battery technology progressed to the point where rapid recharges in the 5 minute range were possible (and this is already here, by the way), we could start building towards pure electric. All the while, our foreign oil dependence was drastically reduced.

Oh, I'm ready for people to pick this apart, but anything can be picked apart if you look close enough. A concept such as this could be put into place. If one of our leaders had such a vision, he could sell the American public on an idea, much the same way Kennedy set our sights on going to the moon. A vision of energy independence is no less grand.

tom deplume

Converting ethanol to hydrogen is about the dumbest idea I've seen. It means not using the solar energy stored in the carbon.


If you are referring to what I wrote, the idea is to BYPASS ETHANOL ENTIRELY, which is what the sugar-to-hydrogen process accomplishes. All the data I've seen suggests it's far more efficient than using ethanol as the energy carrier.

Scott Kruse

Ethanol is still a hydrocarbon - with accompanying air quality problems. This will be an okay short-term measure, but we need a focused effort toward photovoltaic PHEVs for a goal of zero emissions. PV will help to bypass hydrocarbon fuels.


One post I read in this thread stated that right now it is cheaper to drive 100 miles on gasoline than it is to drive on ethanol, and the real solution lay in mass transit denser housing population etc. Well, in response, mass transit vehicles require fuel to operate
as well. These are to seperate issues from within that need to be tackled seperately. Back to ethanol, I cannot imagine that it would be cheaper to transport gas to the United States from other countries, at least in the long run. You would create jobs out the wazoo
within the US, and reduce foreign dependency

Adrian Akau

A good solution would be to develop more wind energy to the grid system for plug in vehicles. Another way would be to use hydrogen-oxygen gas from an on board generator fed straight to the engine via the air intake, a system that has already been developed and proven to increase mpg and reduce pollutants. Burning of ethanol will save little energy but at the same time increase the carbon dioxide burden. The promotion of ethanol means the development of an artificial energy industry which is bound to fail in the long run.

John Kirkpatrick

While I'm sure that this study included some calculation for value from the distillers grains left from the fermintation process, how much is not clear to me from a quick reading. One of the largest problems facing current (summer of '06) large producers of ethanol, is how to get rid of the left-overs, i.e., the distillers grains and solubles. Using it in animal feed is great, but the fact is, at the present time, we are producing much more of these products than can be consumed, using this method. If we are going to increase ethanol production by X times, whatever that number is, how are we going to use the increased volume of by-products? If this comparison study allocated some economic benefit in their spread-sheet for the by-products, and in the end we generate so much of these products that we can't use them, then is there any 'real' value to these products? Large current producers are trying to use more and more of these by-products in animal feed, and are still not using it all up. How are we going to use all the extra stuff from future production?


If you have a car that runs on corn then why arnt we make other engey sources run of the corn to other fueled thing?


Why are they saying it will make are world better ans yes i belive it will but what about the chemicals in the corn? Could that be a harm to our air supply? <3 shelly webster


Why are they saying it will make are world better ans yes i belive it will but what about the chemicals in the corn? Could that be a harm to our air supply? <3 shelly webster

Aishatu Dambam

What is the current situation on research done about the use of lignocellulose for ethanol production. how soon will this technology be available for commercial production of ethanol

Ethanol is way better (enviormenyally)than gasoline duh!!

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Mick Taylor

A conversion to ethanol will be disasterous for the world. Farmers will gladly switch to growing corn in order to satisfy the insatiable need for ethanol. Food prices are rising fast and will go much higher. Milk and cheese prices have gone up 20% and so is the price of eggs and chicken. Rice is rising 30% and there are shortages. Every food product is already getting more expensive. What will happen when crops fail due to weather variations causing periodic drought or flooding? Prices will rise and there will be scarcity of food and fuel! The poorest people of the world will be hit the hardest. Fat Americans can still sit around and stuff their faces with pizza and burgers even if the prices double. But if you are poor and living in Mexico, Latin America, Africa or Asia, the doubling of food prices leads to starvation and malnutrition. And what about the environment? Growing more food will lead to more fertilizers being used and doubling or tripling of nutrients into our rivers, lakes and streams which will KILL them. Do you people know anything about the world or the environment? You endeavor to reduce greenhouse gas emissions, but even the UN has said that even if we reduce to the 1990 levels of C02 emissions, we will have no effect on global warming. So you are willing to endanger the lives of hundreds of millions of people to have NO effect on global warming. That is criminal. You environemtalists are the problem. If the United States had been building nuclear power for the past 40 years, we would all be driving electric cars today, we would be energy independent and the environment would be cleaner. But you oppose all progress and come up with solutions that don't solve problems, instead they create more.

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