Petrol: Denmark wants to phase out MTBE

In step with the removal of lead from petrol and the reduction in its content of aromatic compounds in order to improve air quality, MTBE (methyl tertiary-butyl ether) has been added to petrol in Denmark and a number of other countries to keep up its octane rating. The switch to MTBE as a substitute for lead and aromatic compounds has resulted in considerable improvement in the quality of the air.

In the past years, however, increasing concern has been expressed regarding MTBE's special properties in relation to groundwater. The main problem is that MTBE is easily soluble in water and only degrades very slowly in groundwater. Moreover, as the presence of MTBE at even very low concentrations causes taste and odour problems, a very small amount of MTBE can render a very large quantity of groundwater unfit as a drinking water resource. This is particularly worrying in Denmark as our drinking water supply is based on naturally pure groundwater.

Fortunately, extensive MTBE contamination of water supply wells has not yet been detected in Denmark. We know that numerous incidents of MTBE spillage to the groundwater from petrol stations has taken place, though. Given MTBE's special properties in water, we have justifiable grounds to fear that the substance will spread to the water supply wells. In Santa Monica in California, this fear has long since become a reality in that 70% of the town's drinking water supply was contaminated with MTBE in 1996.

It has been claimed that it should be possible to solve the MTBE problem simply by ensuring that the storage tanks at petrol stations are leak-proof. In Denmark we do not fully subscribe to this view, however. It is clear that leak-proof tanks will reduce the MTBE problem, just as it would reduce emission of other undesirable petrol and oil products to soil and groundwater. We are therefore in the process of drawing up more stringent regulations for petrol station storage tanks based on the use of the best available technology. Not even the best technology can completely guarantee against leakage, however, so the more stringent petrol station regulations concerning MTBE are supplemented by other initiatives to limit or completely phase out MTBE:

The Danish Minister for Environment and Energy, Svend Auken, has thus contacted the EU Commissioner for the Environment, Margot Wallström, to have the MTBE problem raised on the EU agenda with a view to the phase-out of the substance.
In order to limit consumption of MTBE in Denmark, the Danish EPA initiated a campaign in spring 2000 to encourage motorists to switch from 98-octane petrol if their car is able to drive on 95-octane petrol. The rationale is that many motorists use MTBE-rich 98-octane petrol in cars that are perfectly able to drive on 95-octane petrol, which contains considerably less MTBE.
The possibilities for imposing a levy on MTBE are currently being discussed in Denmark. A levy would increase the incentive for the refineries to find environ-ment-friendly alternatives to MTBE.

In Denmark, we believe that MTBE has outlived its usefulness. Although the substance has helped solve pressing problems with air quality, in the longer term this must not take place at the cost of the drinking water.

Further information: Bo Barrensøe, Danish EPA. Phone: +45 3266 0454. E-mail: bba@mst.dk'>bba@mst.dk

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