Are fuel ethers considered renewable fuel components?

The EU Renewable Energy Directive (2009/28/EC) lists ETBE, MTBE and TAME as renewable fuel components provided they are produced using bio-methanol or bio-ethanol.

Are there any safety or environmental concerns about petrol containing fuel ethers?

Petrol  should not be allowed to contaminate soil or groundwater. In most countries, strict regulations exist to prevent petrol leaks and spills, unfortunately these are not always properly enforced. Oil companies, their distributors and retail site operators have comprehensive procedures in place for the safe storage and handling of petrol.

No component of petrol, including fuel ethers, is capable of seeping through properly designed, constructed, tested and maintained systems. A responsible attitude and good operating practices will prevent leaks and spills, and the resulting contamination of soil and groundwater. Nevertheless, human error or equipment failure may lead to an accidental release. In such cases, immediate steps must be taken to deal with the situation. Delays or attempts to cover up the incident can lead to more serious pollution, greatly increased clean-up costs and significant legal penalties.

Are there benefits (or concerns) with the use of fuel ethers on vehicles and their components?

Ethers have been successfully used in Europe for 40 years at levels up to 15% and the Fuel Quality Directive 2009/30/EC permits levels up to 22% v/v.

Can releases of fuel ethers in soil and water be cleaned up?

Yes, fuel ether contamination can be cleaned up in the soil and water by using well-proven remediation technologies such as air stripping, granular activated carbon (GAC), advanced oxidation, and soil vapour extraction (SVE).

Traditional “pump and treat” technologies available for water plants have been proven effective in remediation of petrol-contaminated water, even if it contains fuel ethers. In the event of a contamination incident, activated carbon cartridges installed at the tap could be utilised as a temporary solution. These household filters have been commonly used for many years by private consumers to remove off-taste and odour from drinking water, and the devices work well for petrol components, including fuel ethers. No matter what method is used, the key issue in groundwater remediation is immediate action to eliminate the contamination source, usually a piece of leaking equipment or contaminated soil.

The problem of fuel ethers in groundwater is not inherent to the products themselves, but can arise when the products are not handled correctly.

Further reading: Fuel Ethers and Groundwater

How are ethers produced?

Ethers are synthesized by combining an alcohol and an olefin by a chemical reaction. The chemical name of the ether reflects the two starting materials. For example, ETBE is ethyl-tertiary-butyl ether and is synthesized by reaction of ethanol and isobutene. MTBE is methyl-tertiary-butyl ether, and is synthesized by reaction of methanol with isobutene. In case of the bio-ether, a bio-based alcohol is used.

What are fuel ethers?

Fuel ethers (MTBE, ETBE, TAME and TAEE) are efficient fuel components which enable cleaner burning of petrol in engines.  They act as octane boosters to replace unwanted compounds such as metal-organics, aniline and its derivatives, aromatics that have critical technical or toxicological properties.

Oxygenates are blended into petrol in two forms: alcohols or ethers. MTBE (methyl tertiary-butyl ether) and ETBE (Ethyl- tertiary-butyl ether) and are the most commonly used ether oxygenates, followed by TAME (Tertiaryamyl -methyl ether). European fuel specifications allow them to be blended into petrol in any proportion up to 22% v/v.

Ethers can be both bio-based (e.g. bio-ETBE produced with bio-ethanol) and non-bio-based. The technical properties when used in fuels do not change.

Further reading: Ethers

What are the advantages of ETBE blending compared to ethanol blending?

ETBE features very different and advantageous physical and chemical characteristics, compared to ethanol, when blended into petrol. These include:

  • significantly lower blending volatility,
  • no significant distortion of the distillation curve,
  • better tolerance of wet distribution systems,
  • double the octane increase per “barrel” at equivalent ethanol content and narrower octane sensitivity,
  • better material compatibility.

When ETBE is co-blended with ethanol in petrol, those characteristics entail a whole series of practical advantages, including: 

  • positive economic impact by mitigating the need to remove light components such as butanes/pentanes,
  • reducing risk of phase separation in the presence of water,
  • better compatibility with seals and gaskets,
  • octane sensitivity in line with finished petrol specifications requirements.

Such a “co-blend”, implying a reduced volume of alcohol movement and management at terminals, also allows significant logistic advantages, e.g.:

  • reduced movements of ethanol to terminals,
  • smaller tank size requirements,
  • lower logistical complexity, lighter administrative burden.

Last but not least, ETBE provides a series of environmental benefits compared to ethanol used alone, such as lower VOCs emission, lower permeation losses in the vehicle, and additional CO2 emissions reduction due to less severe refinery operations.

What are the benefits of using fuel ethers in petrol?

Fuel ethers are high-octane, efficient petrol components, which can immediately enable CO2 reductions from petrol vehicles via improved fuel efficiency. They also reduce emissions of harmful air pollutants from passenger cars.

 In the case of MTBE, typical emission reductions are:

  • Carbon dioxide (CO2): Replacing directly blended ethanol with ETBE can save 4 million tons per year of CO2 emissions
  • Carbon monoxide (CO): Emissions are reduced on average by at least the same percentage as MTBE content in petrol.
  • Unburned hydrocarbons (HCs): For each 1 or 2 % of MTBE, there is a 1 % reduction in total HC emissions.
  • Particulate Matter (PM): It is estimated that each 1 % of MTBE results in a 2 to 3 % PM emission reduction.
  • Volatile organic compounds: Fuel ethers can save more than 50,000 tonnes per year of VOC emissions compared with other blending components.
  • Ozone: MTBE generates about half the ozone compared with isooctane /alkylates and one-tenth that of aromatics.
  • Benzene: For each 1 % of MTBE there is an equivalent percentage reduction in benzene emission, both evaporative and exhaust. As benzene is a class 1 carcinogen such a replacement is important.

In addition to air quality benefits, fuel ethers offer an effective substitute for lead, a toxic compound that has been phased out in most parts of the world. It can also effectively substitute other harmful components including metal organic components (MMT), aniline and derivatives.

Further readingFuel Ethers Benefits and Uses

What are the greenhouse gas impacts from petrol containing bio-ethers?

Studies undertaken by an American consulting firm Hart Energy and Dutch CE Delft both showed that ETBE offered an additional CO2 saving versus ethanol; typically 24kg of CO2-equivalent/GJ. In effect, replacing directly blended ethanol with ETBE can save 4 million tons per year of CO2 emissions.

The saving occurs because blending ETBE results in more pronounced modifications of the refining operations as it provides the petrol pool with more octane barrels than ethanol alone. This more than compensates for the energy consumed by the additional processing step.

What are the impacts to vehicle seals with higher dosages of fuel ethers?

Ethers such as MTBE have been commercially used in petrol for more than 40 years.  While alcohols blended into petrol at higher concentrations and under certain conditions may present a compatibility issue with some materials found in the vehicle fuel systems, the ether versions of the same alcohols will usually be much more compatible with the metals and the non metals (elastomers and plastics) that are commonly found in the vehicle fuel systems and fuel distribution systems.

Compatibility with non-metal materials has the potential to become an issue as the concentration of oxygenates (alcohols and ethers) are increased in fuels as a means of reducing the dependency on crude oil for producing transportation fuels. Various elastomers, rubbers and plastics are used by OEM (original equipment manufacturers) for sealing and containing liquid fuels in closed systems such as automotive vehicles, non-automotive small engines, bulk fuel storage and fuel distribution systems. The performance properties of some elastomers may alter when in contact with fuels containing higher volume concentrations of some oxygenates which can then contribute to higher permeation of evaporative VOC emissions (volatile organic compounds) and possibly shorter service life (lower durability).

What are the implications to the environment with the use of fuel ethers?

The EU Risk Assessment on MTBE concluded that there was no need for additional risk reduction measures in addition to those in place for MTBE.

It however identified a need for specific measures to limit the risks in relation to the aesthetic quality of ground water (taste and odour). These proposals recommended, as part of the Risk Reduction Strategy, the application of the best available techniques for the construction and operation of petrol underground storage and distribution facilities at service stations, and that harmonised technical standards for the construction and operation of the storage tanks be developed at a European level by the European Committee for Standardisation (CEN). The EU standard for storage tank construction (EN 12285-1) was published in 2003 and requires them to be double walled with proactive leak detection.

Europe choses to focus on the standards for construction and operation of petrol underground storage and distribution facilities at service stations, including identifying local factors such as use of groundwater and soil migratory conditions.  This is important as petrol, whether or not ethers are present in it, needs to be managed so as prevent contamination of groundwater.

Further reading: Fuel Ethers Risk Assessments

What are the potential health concerns regarding the use of fuel ethers?

The human health impact of MTBE has been extensively studied, with the first tests screening health risk conducted more than 30 years ago. MTBE has never been classified as toxic or carcinogenic by any regulatory body anywhere in the world.

There have been numerous toxicological studies of MTBE, none of which indicates that MTBE is a cause for concern. For example, the WHO International Programme on Chemical Safety (IPCS) says that “based on collective evidence, it appears unlikely that MTBE alone induces adverse acute health effects in the general population under common exposure conditions” (2005 WHO Guidelines on MTBE in drinking water).

ETBE, MTBE and TAME have been subjected to the EU risk assessment process to a greater or lesser extent. The Risk Assessment Reports for MTBE and TAME were published in the Official Journal of the European Union on 4 December 2001 and 21 June 2008, respectively. Whilst ETBE has been subject to a call for a reduced data set under Article 12 (2) of the Existing Substances Regulation (EEC No 793/93; Commission Regulation 1217/2002). The completed data set was reviewed by the EU Technical Committee on New and Existing Substances in November 2005. After these comprehensive reviews, the EU concluded that fuel ethers are unlikely to present a hazard to health or the environment under normal handling and use conditions.


Further reading: Fuel Ethers Risk Assessments

What are the storage and handling guidelines with regards to the use of neat and blended fuel ethers in petrol?

A study undertaken by the European Commission has demonstrated that requirements governing the construction and operation of the Underground Storage Tanks (UST) systems are in place across much of the EU to safeguarding water quality in Europe.
Generally, all technical requirements and operational practices which apply to petrol are applicable for neat ETBE and MTBE and also petrol containing them. However with the following areas requiring specific attention:

  • Gasket materials compatibility to be checked
  • Vapour recovery design, capacity to be checked
  • Storage tanks should have floating roofs and domes
  • Tank bottom water phases to be directed to adapted waste water treatment
  • Special emphasis on leak prevention/detection and soil/groundwater protection
  • Emergency response: oxygenates-compatible extinction foams, adsorbents
  • Minimised response time for soil/groundwater remediation in case of a leakage or splash
  • Medical emergency response (MSDS)

With respect to spills or leaks, owners and operators of installations that handle petrol should be well aware of local, regional and national regulations and legislation. As a minimum, it is recommended to alert local water authorities in any major petrol spill or leakage whether there are fuel ethers or other oxygenates involved or not. The same applies even for small spills and leakages in sensitive areas. More details are available in the MTBE Resource Guide.

Unlike most ethers, MTBE does not tend to form peroxides (auto-oxidise) during storage.
However, ETBE can form peroxides in the presence of oxygen gas or oxidative agents. The peroxidation reaction is slow in typical storage conditions, but it is enhanced by the UV light. Peroxides in ETBE reduce its octane performance very rapidly even at low concentrations. Higher peroxide concentrations can catalyse gum formation and even lead to breakdown into corrosive acids. Therefore, peroxide formation during storing of neat ETBE should be prevented by the addition of an adequate quantity of a typical petrol antioxidant agent such as phenylene diamine. When used in petrol blends, no additional stabilization is needed due to the presence of ETBE.

Appropriate emergency notification and response systems for fire and spill management should be in place at each facility where MTBE & ETBE are received, stored, or used. They should be handled only by workers trained in safe handling methods and response to emergencies such as spills or fires.

Further reading:

Code of Best Practice for Fuel Ethers

2009 Update on Code of Best Practice for Fuel Ethers

What can other regions learn from the European clean air legislation?

The EU approach to emissions standards has been widely copied and it is not unusual to see references to new national standards as being “Euro 3”,”Euro 4” or “Euro 5” equivalents. However, the importance of the fuel in enabling these emissions standards is sometimes overlooked.

Any country wishing to take advantage of the European experience should always ensure that it matches its fuel standards to the needs of the new vehicle emissions technologies. It is worth noting that one of the benefits of fuel ethers is that their positive effect on the petrol pool will immediately result in emissions benefits irrespective of the vehicle car park.

Japan ETBE implementation is a success story of transforming into nearly 100% ether usage. The implementation followed a multi-agency and stakeholder involvement based on sound science. Currently, Japan consumes approximately 1.6 million metric tonnes of ETBE per year.

What is Europe doing to address climate change and reduce CO2 emissions from fuels?

The European Union began to focus on renewable energy in transport fuels when the Biofuels directive (2003/30/EC) was adopted. This initial attempt to foster the development of biofuels was justified by three objectives: reduction in CO2 emissions, improved security of supply and support for the rural economy. This has been further strengthened and refined in two major directives: the Fuel Quality Directive (FQD) (2009/30/EC) and the Directive on the promotion of the use of energy from renewable sources (RED) (2009/28/EC). Here the emphasis is to address the climate change challenge by imposing minimum levels of renewable fuels in transport, and specifically biofuels. The directives also set targets for the reduction, in the entire life cycle of petrol and diesel fuels, of greenhouse gas emissions per unit of energy, and for minimum standards for the CO2 reductions of individual biofuels, the so-called “sustainability criteria”.

The introduction of the 2003 Biofuels Directive saw a major shift in EU ether production from MTBE to ETBE as it provided the oil industry with a “drop in” solution for the rapid introduction of bio-petrol, ETBE being substantially similar to MTBE, and easier to blend than ethanol

The two new European directives have also recognised the ability of ethers to deliver emission savings by setting default values of CO2 reduction “equal to that of the ethanol production pathway used”.

What is the most commonly used fuel ether today?

Methyl-tertiary-butyl-ether, or MTBE is the most commonly used fuel ether in Europe, followed by the biofuel Ethyl -tertiary-butyl-ether, or ETBE, the tertiary-amyl-methyl-ether, or TAME, and finally tertiary-amyl-ethyl-ether, or TAEE.

Further reading: Fuel ethers – Benefits and Uses

What other CO2 savings do ethers offer?

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, both respected independent consultants, using their own in-house modelling systems showed that ETBE offered an additional CO2 benefit over direct ethanol blending.

The studies support the following conclusions:

  • By using ETBE a refiner uses less refinery fuel when producing finished petrol than when using ethanol instead. This energy efficiency means naturally less CO2
  • By maximizing ETBE, production and ETBE usage a refinery can further reduce its CO2 footprint.
  • ETBE typically offers an additional saving of 24kg of CO2-equivalent/GJ of ethanol.
  • Replacing directly blended ethanol with ETBE can save 4 million tons per year of CO2 emissions

Hart Energy Consulting study on TAEE, shows that reduction of CO2 is a general benefit for bio-ethers.

Why use fuel ethers?

Fuel ethers have many properties making them excellent petrol components for environmental and technical reasons. Their high performance, cost-effectiveness and ease of blending make them ideal substitutes for other fuel additives/components.

Lead was traditionally added to petrol to prevent engine “knock”. Lead is, however, a toxic compound, and petrol which contains lead deactivates catalytic converters. For these reasons, it has been phased out in almost all areas of the world.

Fuel ethers have high performance characteristics and are ideally suited to produce unleaded petrol. Adding oxygen to petrol allows more complete combustion of the fuel and this reduces exhaust emissions of CO (carbon monoxide). When used as part of the petrol formulation, ethers lead to a reduction in emissions of exhaust pollutants such as VOCs (volatile organic compounds) and PM (Particulate Matter). Reducing these pollutants improves air quality.

Further reading: Fuel Ethers – Benefits and Uses