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Fuel ethers are additives that promote the better and cleaner burning of gasoline in engines. They are a type of oxygenate, that is, a compound containing oxygen in a chain of carbon and hydrogen atoms. In vehicle fuels today they work as boosters to replace more toxic and carcinogenic compounds such as lead.
Oxygenates are blended into gasoline in two forms: alcohols or ethers. MTBE, is the most commonly used ether oxygenate, followed by the fast growing biofuel ethyl-tertiary-butyl-ether, or ETBE, and tertiary-amyl-methyl-ether, or TAME. European fuel specifications allow them to be blended into gasoline in any proportion up to 15%.
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Fuel ethers have many properties making them good gasoline components for technical and environmental reasons. Their high performance, cost-effectiveness and ease of blending make them ideal substitutes for other fuel additives.
Lead has traditionally been added to gasoline to prevent engine "knock". Lead is, however, a toxic compound, and leaded gasoline deactivates catalytic converters. For these reasons it has been phased out in most areas of the world, including Europe.
Ethers have high performance characteristics and are ideally suited to produce unleaded gasoline. Adding oxygen to gasoline allows more complete combustion of the fuel and this reduces exhaust emissions of CO (carbon monoxide). When used as part of the gasoline formulation, ethers lead to a reduction in emissions of exhaust pollutants such as VOCs (volatile organic compounds), NOx (nitrogen oxides) and PM (particulates). Reducing these pollutants improves air quality.
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Fuel ethers are used almost exclusively as gasoline performance enhancers, although minor amounts are used as solvents. They represent between 2 and 3% of the European gasoline pool.
According to the most recent revision of the European fuel quality standards, Directive 2003/17/EC, the Commission has to publish annually a report on actual fuel quality in the different Member States. The latest report is for 2004 and this shows that oxygenates were used to some level in at least one of the gasoline grades sold in every one of the 12 Member States for which data were received.
EU Fuel Quality Monitoring Report (figures 2005):
 
There are over 50 production plants for ether oxygenates in Europe, with a total capacity of approximately 5.75 million tonnes. 85% of this capacity is installed within the EU27.
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Yes to both. Natural gas, one or the alternative sources of energy as defined by the European Commission, can be the basic raw material of both MTBE and ETBE. The Biofuels Directive, issued in 2003, specifically lists bio-ETBE and bio-MTBE as biofuels due to their renewable energy content.
In a context of increasing demand for road transport, reduction of EU oil production over the next 20-30 years and commitment to reduce greenhouse gases emissions under the Kyoto Protocol, Europe faces a major challenge to build a coherent energy policy. To launch the debate, the European Commission published in December 2000 a Green Paper.
Titled "Towards a European strategy for the security of energy supply", COM (2000)769, this paper sets the objective to achieve 20% substitution of fuels by alternatives in the road transport sector by 2020. Other Commission objectives are to reduce the EU’s dependency on external oil supplies and contribute to reducing emissions of greenhouse gases.
Natural gas, powering vehicles with specifically-designed engines, is one of the main alternative sources of energy contemplated by the European Commission. As it is also the raw material for the production of ETBE, MTBE and TAME, this same natural gas is available today, at no extra development cost, to fuel traditional vehicles.
In May 2003 the European Commission published a directive (2003/30) designed to promote the usage of biofuels and other alternative fuels in road transport. The directive requires that all Member States set indicative national targets for the proportion of biofuels in all gasoline and diesel fuels sold on their market; and proposed as reference values a 2% minimum by the end of 2005, and 5.75% by 2010.
This was followed by directive 2003/96 on the taxation of energy products, which allows Member States to apply a total or partial tax exemption to biofuels.
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Yes, alternatives do exist but fuel ethers remain the best in terms of air quality benefits, cost, and availability.
Alcohols are potential renewable alternatives to fuel ethers and non-renewables include aromatics, alkylates and isomerates.
When Europe started to phase down lead additives in petrol in the 1980s, many refiners replaced them with aromatics, which represented the lowest-cost alternative at the time.
Towards the end of the 1990s, new environmental regulations started to limit the aromatic content of gasoline. A convenient replacement for aromatics was MTBE, a high octane, easy-to-blend, reasonable cost oxygenate, which was essentially a drop-in blending component for the refiner.
The adoption by the European Union of the Biofuels Directive, 2003/30, in 2003 created renewed interest in ethanol use in gasoline. However the automotive and oil industry have always preferred ethers rather to alcohols, such as ethanol, for technical reasons. Adding ethanol to gasoline also increases the volatility of the gasoline and thereby causes an increase in the emission of volatile organic compounds (VOCs).
Furthermore, studies in the USA ("Fate and Transport of Ethanol in the Environment", Malcolm Pirnie) have found that when petrol-containing ethanol leaks into the environment, the ethanol causes other components, such as benzene, toluene and xylene (all among the most hazardous components of petrol) to become 25% more soluble in water.
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