Fuel Ethers improve Air Quality and reduce GHG emissions
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Fuel Ethers improve Air Quality
Adding oxygen to gasoline allows more complete combustion of the fuel and therefore reduces exhaust emissions of carbon monoxide (CO). When used as part of the gasoline formulation, ethers lead to a reduction in emissions of exhaust pollutants such as volatile organic compounds (VOCs) and particulates (PM). Reduction of the above improves air quality.
Likewise fuel ethers have naturally high octane numbers. Normally a refiner has to invest a lot of time and energy into raising the octane of gasoline blending components. Achieving this by using ethers allows refiners to substitute other components which are more energy intensive to produce, and/or have less desirable environmental properties e.g. aromatics and olefins.
Direct and indirect effects of adding fuel ethers to gasoline
Fuel Ethers reduce Greenhouse gas emissions
The greenhouse gas (GHG) reduction that is achieved by using biofuels is receiving increased regulatory and public attention. The production chain for the various biofuels is often complex and highly variable making correct "field-to-wheel” assessment difficult. The bio-ethers ETBE and TAEE have been shown to offer GHG additional savings compared to the bio-ethanol used in their manufacture. This is because the energy saved when a refiner exploits the high octane and reduced volatility they deliver more than counterbalances the extra processing step involved in converting the bio-ethanol to the bio-ether.
Studies carried out by Hart Energy Consulting and CE Delft (1,2), both respected independent consultants, using their own in-house modeling systems showed that ETBE offered an additional CO2 benefit over direct ethanol blending.
The studies support the following conclusions:
- Blending ethers into gasoline is more energy efficient (= less CO2 emissions) than blending ethanol into gasoline. Indeed, pure ethanol blending requires a base gasoline that has a lower RVP compared to a base gasoline in which ETBE is blended. Producing a lower RVP base gasoline increases energy consumption in a refinery because the base gasoline requires more processing in order to compensate for the higher RVP of the ethanol.
- Ethanol in the form of ETBE allows for more efficient transport from the source to the pump compared to ethanol which reduces CO2 emissions.
- ETBE decreases crude oil and lowers refinery energy consumption for crude oil processing and octane production and hence reduces CO2 emissions.
- ETBE typically offers an additional saving of 24kg of CO2-equivalent/GJ of ethanol.
It should be noted that the above mentioned CO2 reduction is small compared to the total refinery footprint. However it is significant when considering the greenhouse savings obtained by using ETBE instead of ethanol.
Hart Energy Consulting has also recently completed a follow-up study on TAEE (3) which shows that this is a general benefit for bio-ethers.
Further reading
Fuel Ethers and Air Quality
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(1) Study on relative CO2 savings comparing ethanol and ETBE as a gasoline component, Hart Energy Consulting, July 2007
(2) ETBE and ethanol: a comparison of CO2 savings, CE Delft, October 2007
(3) CO2 reduction of TAEE vs Ethanol, Hart Energy Consulting, October 2010