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Stanford Study on Ethanol Emissions Generates Counter Arguments and Rebuttal

Last week’s publication of an article in Environmental Science & Technology (ES&T) by Stanford University professor Mark Jacobson, in which he projects that fleet-wide use of E85 in the United States could increase the number of respiratory-related deaths and hospitalizations (earlier post), has stimulated counter arguments from several groups, including various state American Lung Association organizations, the Natural Resources Defense Council (NRDC) and the American Coalition for Ethanol.

In his paper, Jacobson concluded in the abstract that “Due to its ozone effects, future E85 may be a greater overall public health risk than gasoline. However, because of the uncertainty in future emission regulations, it can be concluded with confidence only that E85 is unlikely to improve air quality over future gasoline vehicles. Unburned ethanol emissions from E85 may result in a global-scale source of acetaldehyde larger than that of direct emissions.

In remarks outside the paper, Jacobson was somewhat more aggressive in characterizing the results of the study.

Today, there is a lot of investment in ethanol, but we found that using E85 will cause at least as much health damage as gasoline, which already causes about 10,000 U.S. premature deaths annually from ozone and particulate matter. The question is, if we’re not getting any health benefits, then why continue to promote ethanol and other biofuels?

There are alternatives, such as battery-electric, plug-in-hybrid and hydrogen-fuel cell vehicles, whose energy can be derived from wind or solar power. These vehicles produce virtually no toxic emissions or greenhouse gases and cause very little disruption to the land—unlike ethanol made from corn or switchgrass, which will require millions of acres of farmland to mass-produce. It would seem prudent, therefore, to address climate, health and energy with technologies that have known benefits.

The American Lung Association of the Upper Midwest—a strong supporter of the use of E85—countered first by focusing on the assumption in the study that all vehicles will be operating on E85 in 2020.

E85 was never intended as a complete gasoline replacement, and will only be capable of achieving a portion of the total US fuel demand. Additionally, the areas of the county where this study demonstrates E85 to have the most harmful effects are where E85 is not currently manufactured or sold, making them the least likely areas of concern.

Additionally, the ALA noted that while ethanol-based fuels may increase the emissions of aldehydes, it reduces two air pollutants linked to cancer, benzene and butadiene. (Both those results of the use of ethanol fuels are reported in the Jacobson paper.)

Finally, the American Lung Association noted that Jacobson had not addressed the reduction in carbon dioxide emissions associated with the use of E85.

The NRDC identified what it characterized as a number of flaws with the paper, and recommended two steps to clarify the results of the paper, and take action if warranted:

  • First, that a team of leading vehicle emission experts review the existing data on emissions from E85. Based on this review, if the panel believes the emission scenarios in Dr. Jacobson’s study are incorrect and/or additional sensitivity runs are necessary, air pollution regulators should re-run the air pollution model to develop a broader scientific consensus of the impacts on air quality.

  • Second, based on the results from the above work, NRDC urged the CARB, US EPA, automakers and the ethanol industry to commit to additional testing of E85 vehicles if warranted. If such testing results indicate a need, we call upon CARB and US EPA to immediately set tighter emission standards on E85 vehicles to protect public health.

NRDC made a number of pointed comments on the contents of the paper, including:

  • The study finding conflicts with findings by US EPA, US DOE and NREL that found that E85 can reduce emissions of smog-forming chemicals.

  • The study’s assumption that E85 emissions are substantially different than those of gasoline is incorrect.

  • The study’s findings are primarily driven by assumed decrease in NOx.

  • The study ignores the potential global warming pollution reductions from E85 and the smog impact of rising temperatures caused by global warming.

In conclusion, the NRDC said,

The author’s comments surrounding the release of his study overstate what the study actually shows. An accurate summary would be that this study shows that use of high blend ethanol is unlikely to significantly improve air quality compared to use of gasoline.


In response to all of the above plus other comments in the press and from other organizations, Jacobson published a detailed rebuttal of the various charges on his web site at Stanford (with the promise of additional rebuttal to come, as of 26 April).

As to the general charge of a misleading study due to the assumption of 100% penetration of E85, Jacobson noted:

The study makes no exaggerations as it does not claim that E85 will or is likely to make a 100% penetration. The purpose of looking at 100% penetration was to determine an upper limit of the effects from which the effects of any smaller addition of geographically-dispersed vehicles can be examined. Once the 100% effects are known, the effects of incrementally-adding a few geographically-dispersed vehicles can be estimated. It is the direction of the effects, not the magnitude, that is important in this case.

Nor was he swayed by the argument about greenhouse gases, characterizing the potential reduction, based on recent life cycle analyses, as too low. Concerning the NRDC paper, Jacobson noted:

In this document, NRDC has suppressed information contrary to its argument, misstated assumptions and conclusions in the paper, and failed to comment on the real issue, the comparative disadvantages of both ethanol and gasoline compared with other existing and emerging technologies that nearly eliminate air pollution, climate relevant gases, and use much less land area than corn or prairie grass for ethanol.




"There are alternatives, such as battery-electric, plug-in-hybrid and hydrogen-fuel cell vehicles, whose energy can be derived from wind or solar power."

How many wind or solar power plants would be needed to produce enought energy to power one car? Because of the small amount of power produced by one solar panel, I'm not sure that this would be a good solution from an environmental point of view. Just a few years ago, the production of a solar panel required more energy than it would produce during its whole lifetime. And do we really want vast fields of solar panels and wind farms instead of forests?


before you make your mind up on this one ask someone
that has spent some time in Brazil what the effects of Ethanol
are on the air quality particularly in the urban enviroment .
My brother spent some six months in Brazil a few years ago
working for a phone company and travelled to every major
city in the country , his overriding memory of the time was
the foul stench in all the citys from the use of ethanol.
The fact is that ethanol is just a loophole to enable the
continued use of the infernal combustion engine , and many
years down the we will find out the true cost of this miss use
the air that we breathe .
Recently studies of the air quality were carried out in Oxford
England and it was found that spending a day in the centre of this
small english city had the eqivalent effect on the lungs as
smoking 60 ciggarettes , a sobering thought !

Rafael Seidl

@Andrichrose -

please provide a link to the Oxford city study. As it is, I don't believe your claim.

aussie paul

there have been huge advances in solar energy with multi- junction cells achieving 40% efficiency. these cells can have 500 suns of light energy concentrated on just a handful of them by parabolic mirrors. this development not only increases the energy collected per square metre but will reduce the cost per square metre. i think about half the average house roof area will easily power the average australian home including daily commuting, hot water and heating.
and i stand by my original post which was removed for some strange reason, that biofuels in their present forma are an ecological and humanitarian disaster, and their production needs to be stopped until they can be made without destroying more forests and without using food crops.


Donkeys and carts; that's the ticket!

aussie paul

if you can't dazzle them with brilliance, baffle them with bullshit! Donkeys and carts? I'm baffled.


I am puzzled by such a strong response from the ALA and NRDC. NRDC talks about potential greenhouse reductions. What on earth does that mean?

On the other hand, the NRDC seems to acknowledge that ethanol won't improve air quality. I think this is the key issue in any event. These are alternative fuels, not green fuels. Whether or not they decrease greenhouse emissions is unclear. A recent study concluded that biodiesel would actually increase greenhouse emissions, mainly because of the significant releases of nitrogen. Might the same logic apply to ethanol?

Frankly, I am not particularly concerned with the air pollution effects from ethanol because I don't think it will ever provide for a signficant amount of fuel demand. Keep this is mind. Ethanol is using up 25% of the corn crop but is only providing 3% of our liquid fuel needs.

The primary focus should be on increased efficiency and conservation garnered from smaller and more advanced vehicles, changes in land use patterns, more ubiquitous mass transit, and carbon and/or gasoline taxes. Biofuels are largely a fantasy pushed by politicians and others who don't want to face reality; we must cut back on the use of liquid fuels, regardless of the source.


I see ethanol as an additive to gasoline. We might get to E10 and maybe E20, but E85 is highly unlikely, for the obvious reason that we could not produce the 85% of 150 billion gallons per year.

To me an I.C.E. is a smog pump. No matter what fuel you use, you lose. Eventually, perhaps, we can get to EVs and fuel cells, but until that time, I would not worry about E85 nationwide in the U.S.

As far as energy payback from solar panels, the last estimate was about 3-4 years of operation to pay back the energy used to manufacture the panel. If you do some research, I think you will find that this is true.


Farm fields will NOT be replaced by solar/wind farms.
1st, you can farm right around windmills, they do not shade the crops.
2nd, solar's advantage is that it can be used at the end source, so why would we setup solar in rural areas with little electrical usage? We have PLENTY of buildings with a whole lot of nothing on top. All these building do is absorb heat and increase AC costs. We also have a practically unlimited amount of parking lots that would actually benefit from a little shade overhead from the panels. Plus, if we move to EV's, as most predict, you can plug in while your parked.


If you look online, you will see solar panel covered parking structures. This keeps the car cool and the paint from fading. These structures could recharge PHEVs during the day while at work.

Most people could put enough solar PV on the roof of their home to run their car 40 miles per day. It all costs, but so does gasoline, oil and wars.

Green Destiny

It seems to me that many have conflated CO2 emissions and their associated global warming effects with smog producing emissions and the health effects of burning fuel in densely populated environments.


Skropp, each kilowatt of wind turbine will power one PHEV. If our 200 million cars were all PHEVs we'd need 200 GW of wind turbines. If you assume a 40 year turbine life, that's 5 GW/year. The US will install about 3 GW this year and should install over 5 GW in 2010.

We're already there with wind turbines, we just need to start building the PHEVs!



We won't need to replace the entire car fleet though.
Looking ahead, it will be too expensive for a lot of people to have ANY type of car, whether gas or electric. I would predict in 10 years, we'll have half the cars on the road, and many of them will be electric commuter vehicles. You don't like mass transit or can't work from home? Well you're gonna pay a bunch for the privelage of driving a car every day.

Harvey D.

The problem is our polluting inefficient ICE vehicles and our inefficient polluting HVAC systems.

Using ethanol, especially from food crops, instead of gas & diesel derived from fossil fuel (oil and coal) without changing our gas guzzlers and our HVAC systems is NOT the proper solution.

Progressively switching to a mix of 100+ mpg PHEVs and BEVs could reduce liquid fuel consumption by up to 90% over a 20-year period or so.

The remaining 10% could come from cellulosic ethanol and/or butanol and/or FC.

All the extra electrical energy required for our PHEVs, BEVs and electrical HVAC systems could come from clean sources such as Hydro, Solar, Wind, Waves, Geothermal, (wastes disposal with plasma torches) and Up-to-date Nuclear plants.

PS: Switching to an up-to-date geothermal heat pump/AC with 23-SEER instead of the old air cool 10-SEER unit will reduce energy consumption enough for one or two PHEVs in most places.


How do you power a BEV world? Solar is nice but its a intermittent sources of energy. In a BEV transport system cars are going to be driving around at day or parked by plug-less streets, at night the people will plug in their cars at home, content with the belief that their cars reduce emission. Big problem: the sun not up! What do you think is charging the BEV at night? Smog belching coal! Hydrogen would solve the problem by storing the solar electric energy, but with the price of fuel cells and radical means of storage needed hydrogen cars are not likely to be around any time soon. H2EVgo for ~$1million, BEV ~$100K but an E85 ICEV goes for $15-40K or just $300 more then a Gasoline ICEV. Reducing global warming and increasing air-quality are definite goals, but preparing for and dealing with Peak Oil is a whole other problem. Ethanol made from cellulosic agriculture waste could replace 15-30% of our gasoline demand and could do it now invisibly, this would reduce global warming (by producing a carbon net neutral fuel) but (according to this study) do nothing for our air quality in general, so what? The benefits out weigh its disadvantages: it can be implemented now invisibly, it would reduce global warming, but it does nothing for general air quality, so we should just chuck it and keep with gasoline until a perfect solution appears??? Come on people be realistic, we need to implement as many different energy plans now and have them fight it out over the next few Post-Peak Oil decades until the winners appear. In the end its will probably be hydrogen powering most cars (or maybe even Zinc instead of hydrogen), with biomass and fermentation products like ethanol finding there niche in other things (likes race cars, power tools, small airplanes, jets, plastics, asphalt, and basically the other 50-40% of the oil market that no one notices) until then it’s a piecemeal transition economy where anything goes.

Stan Peterson

It is sophistry about "new" fossil fuel as opposed to "old" fossil fuel when the products are indistinguishable.

Fuel made from current production of vegetative plants or from older vegetative plants (Oil and Coal) is indistinguishable and doesn't change a damn thing with respect to the atmosphere!

Only idiots, politicians, and charlatans can speak of the good or bad of the same fossil fuel when they are not different and the consequence is the same.

Now since I think CO2 has been more recently scientifically been shown, to be an effect and not a cause, of the warming we are seeing. Solar irradiance is globally warming ALL the planets of the Solar System, including Earth. It makes no difference the source of the fossil fuel, even more.

The only true "warming polluter" in that case is the use of Solar Energy which absorbs more than any other absorber of solar radiance, including the perfect black body radiator/absorber.

Where do you think the "Solar Energy" comes from, anyways? You can't repeal the Second Law of Thermodynamics.

It is the net energy removed by a Solar Cell, that leaves the residual to be re-radiated as the lower Albedo, that could be a problem. This would only aggravate warming the Globe even more due to the Solar warming. If they have scared you enough that you lose sleep over that microscopic 'warming', then Solar Energy should be the worst anathema.


Your kidding, right Stan?
The law of thermodynamics states that energy cannot be created or destroyed, it can only be converted.

In a solar panel, the sun energy is converted to electricity, as OPPOSED to converting it to heat energy as asphalt shingles do.


if you can't dazzle them with brilliance, baffle them with bullshit! Donkeys and carts? I'm baffled.

Posted by: aussie paul | Apr 27, 2007 6:31:27 AM

You want to minimize your footprint on the Earth? Find alternatives to automobiles Paul. And consume less. The meek will inherit the earth.


"It is the net energy removed by a Solar Cell, that leaves the residual to be re-radiated as the lower Albedo, that could be a problem. This would only aggravate warming the Globe even more due to the Solar warming. If they have scared you enough that you lose sleep over that microscopic 'warming', then Solar Energy should be the worst anathema."

Currently, yes. However, if we use two stage solar thermal or high temp photovoltaic concentrator systems then the effect will be far less pronounced. The first stage is electric generation whether it be turbines, or photovoltaic cells. The second stage uses excess/waste heat for various purposes. Piping in seawater and using the waste heat as part of a desalination (and chemical/seasalt production) system is one of the many possibilities.
__On a smaller scale, running copper/aluminum water pipes on the underside of rooftop photovoltaic setups for hot water, or at least preheat the tap water before reaching the water heater, may be another way to offset the decreased albedo.


"The meek shall inherit the earth"

Since the time that was written (2000 years ago?),
the exact opposite has been true.
The crusades.
resource extraction from poor countries to rich countries.

Why do think that pattern will change?



Where would one obtain, let alone keep, a donkey and cart in a suburban home? There's little things called zoning regulations that prevent the owning of such livestock. Your suggestion is absolutely absurd.

This is Green CAR Congress. That means sustainable personal mobility. Increasing mass transit may be doable in some localities, but the lack of affordable housing close to employment, suburb-to-suburb commuting, low population density, and other factors prevent it being being practical at scales seen in Europe (which has a much more dense urban population).


Rafael ,
Got the info from the website , must admit did not believe
myself , so I checked it through a friend who works in the air quality
study group here at the European research centre here in northern
Italy and he had seen the study and confirmed its findings as being
more or less accurate , in fact recent tests in and around Milan have
come up with in some cases worse results than the Oxford study.


Rafael ,
Got the info from the website , must admit did not believe
myself , so I checked it through a friend who works in the air quality
study group here at the European research centre here in northern
Italy and he had seen the study and confirmed its findings as being
more or less accurate , in fact recent tests in and around Milan have
come up with in some cases worse results than the Oxford study.


The meek may inherit the earth, but the strong will just take it back :)


and blessed are the cheesemakers!

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