Ethers and Ethanol

Ethers and Ethanol


Studies commissioned by leading regulatory agencies across the world have demonstrated that the use of MTBE reduces permeation—a key contributor to evaporative emissions. The use of MTBE, thus, reduces ground-level ozone and airborne particulate matter formation. The Coordinating Research Council E-65 study (CRC E-65) that was commissioned by the California Air Resources Board, for example, shows that fugitive emissions with 11% MTBE gasoline were 12% lower than with un-oxygenated gasoline.

In contrast, ethanol use significantly increases hydrocarbon permeation from the fuel tank and gasoline distribution system. In its 2014 Evaporative Emissions from On-road Vehicles in MOVES2014 report, the United States Environmental Protection Agency concludes that “ethanol was then seen to have a significant effect compared to E0 fuel (that does not contain ethanol)”. The table below, recreated from the study, summarizes those findings, according to the type of vehicle being used:

acela-ethanol-emissions-increaseU.S. EPA study shows increase in emissions from gas containing Ethanol

In addition to the detrimental effect of ethanol on permeation, the table also suggests that this effect has worsened as the US vehicle fleet modernized. Studies that looked at MTBE and ethanol simultaneously, such as the CRC E-65 study, show that gasoline blended with 6% ethanol increased VOC permeation by 70-74% in pre-2001 vehicles compared to  gasoline containing 11% MTBE and that those fugitive VOC emissions could increase ground level ozone by as much as 55% compared to MTBE-blended gasoline.

Finally, international studies whose methodology is appropriate for analyzing tailpipe emissions (not fugitive ones), have shown that MTBE use also provides tailpipe emissions benefits compared to ethanol. For example, a 2011 study from the Mexican Petroleum Institute (IMP) showed that, with 11% MTBE volume in fuels, formaldehyde emissions and acetaldehyde emissions decreased by as much as 17 and 29 percent, compared to fuels oxygenated with 6% ethanol by volume. Aldehydes, besides being carcinogenic air toxics, are also potent ozone precursors.

Ethers also vaporize more readily during the cold-start cycle, during which 80% of PM is formed.


Ethers vaporize at lower temperatures which means fewer emissions


In addition to reports that look directly at air quality components, recent studies have challenged the notion that the use of ethanol, compared to unoxygenated gasoline, reduces GHG emissions—even when looking at US ethanol production, which is widely acknowledged as leading in terms of agricultural efficiency. For example, a 2016 study from the University of Michigan concluded that «when it comes to the emissions that cause global warming, it turns out that biofuels are worse than gasoline». This represents one more data point that supports the fact that ethers are more “emissions efficient” than all other octane sources, including ethanol.





United Nations Intergovernmental Panel on Climate Change

  • “Since for some biofuels indirect emissions—including from land use change—can lead to greater total emissions than when using petroleum products, policy support needs to be considered on a case by case basis”


U.S. Government Accountability Office

  • “Results from a completed study indicate that such blends [ethanol blended gasolines] reduce a vehicle’s fuel economy (i.e., fewer miles per gallon) and may cause older automobiles to experience higher emissions of some pollutants and higher catalyst temperatures. Results from another completed study indicate that such blends may cause some non-road engines to run at higher temperatures and experience unintentional clutch engagement, which could pose safety hazards.”


The International Council on Clean Transportation (ICCT)
Katherine Blumberg, Mexico Lead, on the NOM-016 (on fuel quality) public consultation process

  • “Due to the great risk associated with high VOC emissions in Metropolitan Areas, we recommend that the CRE considers restricting or prohibiting the use of ethanol in gasoline commercialized in the Valley of Mexico and in any another city where the production of ozone may be correlated to the availability of VOCs.”


Environmental Working Group

  • “Using the EPA’s own estimate, we calculate that the corn ethanol mandate has been worse for the climate than projected emissions from the controversial Keystone XL pipeline. … So far the federal corn ethanol mandate has resulted in a massive influx of dirty corn ethanol, which is bad for the climate and bad for consumers. The only interest it benefits is the ethanol industry. As we’ve said before, it’s time for Congress to correct course and reform the broken RFS to make way for truly green biofuels.”


Natural Resource Defense Council

  • “[W]e don’t need an additional 1.4 billion gallons of corn ethanol, or the higher prices for grains and more deforestation that come with it. … It’s time to transition from corn ethanol’s pollution and pork to a new generation of more sustainable biofuels that brings us closer to real energy independence.”


Clean Air Task Force

  • The (ethanol) program’s main achievement to date—shepherding an enormous scale-up in corn ethanol consumption—has pushed up food prices in the US and around the world and increased GHG emissions, air pollution, water pollution, and habitat destruction.… Worse, CATF’s review of the EPA data found that US corn ethanol production is actually increasing, not decreasing, GHG emissions.”




Ministry of the Environment and Natural Resources
On the NOM-016 (on fuel quality) public consultation process

  • “Ethanol in fuels increases the potential formation of ground-level ozone. Exceeding the acceptable concentration of said contaminant, can increase negative impacts on the environment and public health, particularly in the three metropolitan zones (Valley of Mexico, Guadalajara and Monterrey).”
  • “Ethanol, being hygroscopic, must be blended (into fuels) at the final stage of the supply chain… “it (may) modify the fuel characteristics (such as RVP), there must be evidence that regulatory specifications are fully complied with after (ethanol is added).”


Mexican Center for Environmental Law
Top environmentalist NGO and member of the NOM-016 on fuel quality working group.
Official statement on the NOM-016 results

  • “It has been proven that 10 percent of ethanol in gasolines increases ozone formation by as much as 640 percent in vehicles with Tier 1 technologies and 400 percent among Tier 2.”
  • “With 5.8 percent ethanol, the maximum allowed by NOM-016, it has been proven that hydrocarbons penetration (sic) increases in 60 percent among Tier 0 and Tier 1 vehicles, compared to unoxygenated fuels.”


Mexican Center for Environmental Law
Top environmentalist NGO and member of the NOM-016 on fuel quality working group.
Gustavo Alanis, General Director, op-ed on fuel quality issues

  • “(ethanol) blending should be prohibited in metropolitan zones and member states of the Megalopolis, due to the critical air quality conditions and in line with the latest measures taken by the federal government regarding air quality in the Megalopolis (the pending verification standard, the definitive standards) since using ethanol in these percentages would cause an increase in ozone formation… per vehicle, per day, worsening air quality.”


Mexican Center for Environmental Law
Top environmentalist NGO and member of the NOM-016 on fuel quality working group.
Gabriela Niño, Public Policy Director, on the NOM-016 (on fuel quality) public consultation process

  • “Because of its high potential for ozone formation , we suggest that the use of ethanol in gasoline blending should be banned in metropolitan areas (ZM) and in the states part of the Environmental Commission of Megalopolis (CAMe), in line with the latest measures taken by the federal government regarding air quality in the megalopolis.»


National Chemical Industry Association
Leading Mexican trade association in the chemistry industry.
On the NOM-016 (on fuel quality) public consultation process

  • “The potential introduction of ethanol as a gasoline component in metropolitan areas (MZ), especially in Mexico City, Guadalajara and Monterrey, would worsen the air quality crisis. Ethanol is highly corrosive and known to degrade fuel system seals and increase the permeability of gasoline plastic tanks. This would increase greatly fugitive emissions of hydrocarbons in contrast to gasoline blended with MTBE, currently in use in the MZ.”


Gabriel Quadri, environmental expert
Op-ed on ethanol risks in Mexico

  • “Identifying what is best for the environment can be difficult in a world full of ‘green’ marketing. This is especially true with ethanol’s decades-long campaign to portray itself as a ‘green’ renewable fuel. While many in the U.S. have been drawn to its siren song, thankfully Mexico has examined it with clear eyes and made a wise choice for its future.”
  • “Ethanol’s hygroscopic and corrosive nature makes it incompatible with Mexico’s current distribution infrastructure and vehicle fleet. This was instrumental in CRE reaching its decision to reduce the permissible limits for ethanol, from an implicit 8% maximum under the previous standard, to an explicit 5.8% cap in the new one.”
  • “A series of studies show that ethanol use among older vehicle fleets, like Mexico’s, significantly increase emissions that form ground-level ozone (smog).”


Mexican Institute for Competitiveness
Leading independent think tank on public policy and economic and social performance
Gabriela Alarcón, Director of Urban Development, interview on fuel quality issues

  • “(Potential ethanol use) greatly worries us, that could even end up increasing ozone levels in metropolitan zones. This has proven to not only have negative effects, but also to generate more emissions that are precursors to ozone.“


Luis Carriles, leading energy journalist
About the NOM-016 on fuel quality

  • “The current NOM, and the liberalization of the fuels market, opens the door to the use of ethanol despite the fact that it’s been extensively demonstrated that it increases the potential for ozone formation. Remembering what the last Pemex CEO explained about why it’s a bad idea to use is not trivial.
  • “Do not be fooled by the fools who believe that ethanol is the solution to ozone; a fact, in Rio de Janeiro, Brazil, when not used by drought and lack of product fell ozone.”
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