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Study finds that environmental impact of corn-ethanol E85 is 23% to 33% higher than that of gasoline; environmental problem-shifting

Yang etoh
Environmental impacts of gasoline and E85. Error bar shows regional variations for E85. GW = global warming; Eut. = eutrophication; ET = ecological toxicity; FEC = fossil energy consumption; WU = water use; LO = land occupation; “The rest” includes acidification; smog formation; ozone layer depletion; and human health effects. Credit: ACS, Yang et al. Click to enlarge.

When 12 different environmental impacts and the regional differences among 19 corn-growing states are taken into consideration, E85 (85% ethanol, 15% gasoline) blends made with corn ethanol from dry mills show a worse total environmental impact than gasoline, according to a new study by a team from the Universities of Minnesota, Troyes (France), and California, Santa Barbara.

In a paper published in the ACS journal Environmental Science & Technology, the authors reported that if the impacts are aggregated using weights developed by the National Institute of Standards and Technology (NIST), overall, E85 generates approximately 6% to 108% (23% on average) greater impact compared with gasoline, depending on where corn is produced, primarily because corn production induces significant eutrophication impacts and requires intensive irrigation. If greenhouse gas (GHG) emissions from indirect land use (iLUC) changes are included in the analysis, the differences increase to between 16% and 118% (33% on average).

Although ... previous studies have followed the general framework of life cycle assessment (LCA), they have focused almost exclusively on quantifying the energy balance and GHG emissions associated with biofuels production. Such a narrow scope in environmental impact contradicts one of the core principles of LCA: whereby the results of an analysis are meant to prevent problem-shifting between different life-cycle stages and among different environmental impact categories. The singular emphasis on energy balance and the carbon footprint neglects numerous other impacts associated with biofuels production including those related to irrigation, fertilizer application, and pesticide use for feedstock growth.

In a similar way, the full breadth of impacts attributable to conventional gasoline production, such as natural resource consumption and hazardous pollutant emissions, must also be considered in order to make balanced comparisons to biofuels. Few studies have endeavored to make such comparisons between gasoline and corn ethanol on the basis of such a comprehensive set of environmental impact categories, with no study in particular including more than a few environmental impact categories and an assessment of their relative importance.

—Yang et al.

The new study uses of a life cycle inventory (LCI) database that the team recently compiled under a project funded by the US Department of Agriculture (USDA). The new LCI database covers a wide array of environmental pressures associated with biofuels production including releases of toxic substances and criteria pollutants to air, water, and land; emissions of nutrients that cause eutrophication; consumption of water; and occupation of land.

Process flow diagrams for E85 and gasoline. Credit: ACS, Yang et al. Click to enlarge.

For the study, the team compared the suite of environmental impacts attributable to gasoline with that of corn ethanol produced in 2005, including GHG emissions as a consequence of possible indirect land use change (iLUC), as well as measures of the uncertainty associated with the calculations.

In recognition of the impact of local climate, soil, and topography can all have on corn production, they also conducted an LCA of corn ethanol at the state level and for each of 19 corn-growing states surveyed by the USDA.

This full analysis considered feedstock production, shipment of the feedstock to the refinery, refining/conversion, shipment of the fuel to the refueling station, and vehicle operation. For gasoline, the study reflects the US context in which crude oil is to a large extent imported and refined domestically. They used the amount of fuel required to drive 1 km in an average gasoline-powered car and a flexible-fuel vehicle—both as modeled in the Argonne National Laboratory’s Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model.

They found that E85’s heavy impacts on eutrophication, water use, and land occupation outweigh the modest benefits in other impact categories, such as global warming, ecological toxicity, and fossil energy consumption. To check the robustness of the overall conclusion against different choices of weighting factors, they performed a Monte Carlo simulation. The results of that confirmed the general conclusion that gasoline is more favorable than E85. They also applied an alternative allocation method based on substitution, and found that it did not change the overall conclusions either.

Our study seeks to draw attention to the importance of impacts other than climate change in renewable-energy policies, including Energy Independence and Security Act (EISA), that use narrow environmental criteria. A careful evaluation of environmental impacts other than GHG emissions in those policies would be important to minimize the unintended consequences of biofuel development. Particularly, our analysis shows that addressing eutrophication and water consumption impacts is essential in limiting environmental degradation due to biofuel development. Achieving substantial reductions in the nutrient runoff and water consumption associated with biofuel feedstock production are identified as priorities in the effort to mitigate the overall environmental impact of corn ethanol. For this, our analysis indicates that the significant regional variability in eutrophication and water consumption impacts may play an important role in planning future biofuel feedstock production at minimum environmental costs.

...Given the importance of cultivation stage in the total life-cycle impact of corn ethanol, however, the inclusion of other conversion technologies in the analysis will not affect the central message of our study: that replacing gasoline with corn ethanol may result in problem shifting, especially to eutrophication and local water scarcity.

This study highlighted the environmental impacts of corn ethanol in comparison with gasoline. Biofuel policy, however, needs to consider not only the aggregate environmental impacts but also other socio-economic and political issues which were not analyzed in this study. Biofuel’s potentially positive impacts toward, e.g., energy independence, energy security, job creation, and revitalization of rural economy and stabilization of gasoline price, as well as its other adverse impacts toward, e.g., increasing food price, should be duly considered in biofuel policy.

—Yang et al.


  • Yi Yang, Junghan Bae, Junbeum Kim, and Sangwon Suh (2012) Replacing Gasoline with Corn Ethanol Results in Significant Environmental Problem-Shifting. Environmental Science & Technology doi: 10.1021/es203641p



Once again, the majority was not told the whole truth. Corn ethanol that we all thought was a very clean replacement fuel turns out to be a lot worse than even dirty Tar Sands gasoline. What an awakening!


Probably ethanol is not worst thing . Hydrogen or photovoltaic could be much more worse from carbon footprint point.


Start hydrogen and photovoltaic commercialisation to push gas and ethanol price down and reduce pollution from the oil lobby.


This doesn't surprize me at all.



.... primarily because corn production induces significant eutrophication impacts and requires intensive irrigation....

Well duh!.. corn must be grown responsibly.. and growing corn for ethanol in drought stricken Texas and California is very irresponsible.

Its very hard to compete with free fuel that bubbles out of the ground.. until it runs out.

Dave R

Kind of ironic that this news is right above the news regarding E15 approval.

Presumably any amount of corn-ethanol added to gasoline has a proportional affect.

If E85 increases GHG by 33% on average, E10 increases GHG by 4% on average and E15 increases GHG by 6% on average.

The only thing corn-ethanol might do is slightly reduce oil imports (how much oil goes into a gallon of corn-ethanol?)


@HarveyD, there is no mention or comparison to Tar Sands gasoline. That is a inaccurate and misleading and I can assure you that almost anything is cleaner than tar sands oil.

Furthermore, the fact that they used data from 2005 is ridiculous, as most of the recent energy efficiency developments in the ethanol industry have occurred in the last 3-4 years.

There is simply no comparison in my mind to almost any alternative fuel to petroleum, as the true cost is never taken into account for both environmental and financial concerns with wars, convoy attacks and our military's continued protection of oil shipping lanes around the world.

@ Herm, great comment about the magical, energy dense liquid called petroleum, which currently has 100 million years of free sunlight, heat and pressure head start on all other alternatives.

Humans pump out of the ground over 3 billion gallons of oil a day... not sustainable and not going to last.


About the only thing that won't increase GHG outputs is the use of stuff that's already being grown to make fuel instead of letting it rot.

The USA produces large amounts of biomass as excess cornstalks (must be removed to plant), corncobs, urban "green waste" and municipal garbage.  Recent advances in thermal hydrolysis appear to allow most of the cellulose in these to be converted to 5-carbon and 6-carbon sugars.  These can be fermented with existing techniques, producing fuel without changing any land use or adding to irrigation or fertilizer runoff.  The conversion of green waste and garbage even eliminates tipping fees and transportation to dump sites.

Today's pressurized-water reactors operate hot enough to supply the process heat without emitting carbon.  If there's a way forward, it's going to look something like that.


Here is where the flaw is in this analysis. The assumption is made that corn would not be grown (or any other agricultural activity would take place) if the the ethanol were not being made. But, farmers farm. The presenters of this work would have to tell me that they are only considering the additional corn being grown because now there is a market for more corn, and more land is being farmed than previously, and that the corn specifically grown for ethanol is somehow more impactful than corn grown simply for feed (or other crops). I however know that is not the case for most corn and most farms. For the most part corn is grown for animal feed, and some is converted to ethanol and the protein part, after having the sugars produce ethanol, is sent for animal feed. I assume this was a hatchet job by someone hired to do so. If this is the actual level of intellectual thought going on in the universities now, we are in bigger trouble than I thought.


Bro4...what would your percentage be if corn farms were returned to nature (pasture and/or forest land)?

EU studies recently revealed that fuel from tar sands was 17% dirtier than from regular crude. Assuming that this 17% and the above study are both correct, corn derived ethanol, at certain mixture level, is worse than our very dirty tar sands fuel?

Just amazing, isn't it?


Last time I looked the U.S. had 100 million acres planted in corn, and 30% of that was for ethanol. Use all the corn grain for feed/food and the stover (stalks and cobs) for fuel.

If you want to use cellulose fermentation methods fine, gasify what is left over and make gasoline. Use the heat from the gasoline plant to ferment and distill in the ethanol plant. We are still going to need an oxygenate for cleaner air.

One day we may all be driving electric cars, but not in the next 10 years. In 10 years the price of oil went from $15 to $145 per barrel and we need all the methods at our disposal to keep from being buried by what is coming our way.

One day we may all be driving electric cars, but not in the next 10 years.
Given the recent push to produce silicon anodes for Li-ion batteries, I wouldn't be surprised if in 2020 just about everything in showrooms has idle-stop, BAS-II or the equivalent, and all-electric operation at low speeds with most models offering plug-in capability.

Look what happened in the 20 years from 1990 to 2010, we have faster computers and flat screen TVs, but no flying cars nor fusion energy.

The point being there have been endless projections of a shiny bright new future and it turns out about the same with some changes. These are the ways of humans over time and not wishful thinking.

By 2020 there will be some changes, buy 2030 there will be some more, but one thing I would count on is oil becoming harder to get and more expensive from here on out. 100 million people will NOT be driving EVs in the U.S. in 2020.


corn ethanol has an EROI of 1.6 to 2.0 in the most modern plants, yet it only requires one gallon of diesel to make 21 gallons of ethanol.. the rest of the energy is about a gallon equivalent also, but in NG and coal.. plus sunlight of course.

If we stop making corn ethanol, corn prices will collapse again, the farmers will need price supports and local growers in third world countries will not be competitive with cheap US corn... but it would boost the consumption of gasoline.


Why not buy the corn stalks and cobs from the farmer, instead of letting them rot in the field and turn them into ethanol and gasoline. Then we would not have the incentive for corn grain future price speculators doubling the price of corn.

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