There are around 1.3 million leisure boats and more than
600 000 outboard motors in Sweden. Most of these are traditional
two-stroke engines that have inefficient combustion. Between
20 and 30 percent of the fuel mix in these motors ends up
uncombusted in the water. And the fuel that does burn in the
engine is converted into toxic or carcinogenic substances
in a higher proportion than from a four-stroke engine.
Each year 15 000 tons of hydrocarbons are emitted from outboard
motors on leisure boats in Sweden. Around half of these emissions
remain in the water in small droplets. Outboard motors are
mostly used in a short season that is coincides with the time
when aquatic life is most sensitive. These motors are often
driven in calm, shallow inlets where the rejuvenation of many
water organisms takes place.
The idea of running two-stroke engines on a much cleaner
fuel was raised in a report entitled 'Mindre gift på
drift' which was written as part of the Swedish Government´s
'Archipelago project' (Skärgårdsuppdrag). This
fuel is alkylate petrol. The fundamental idea was to use the
cleanest available fuel for the most polluting engines.
Alkylate petrol is free from aromatic hydrocarbons and olefins.
This means that the emissions of carcinogenic, persistent
and toxic polyaromatic hydrocarbons (PAH) are up to 90% lower
than with conventional fuel. Furthermore, alkylate petrol
has a lower emission of nitrogen oxides and a smaller contribution
to the creation of ground-level ozone.
Alkylate petrol works well as a fuel in two-stroke engines.
Independent tests have even shown that engines show better
performance, clean idling and lower smoke generation than
the conventional fuel. It is, however, important to regularly
check the gasket and pipe work in order to avoid leaks.
Alkylate petrol is a high quality product with limited availability.
It is somewhat more expensive to produce than conventional
petrol and in the past it has had a higher tax. After intensive
pressure from, amongst others, environmental and boating organisations,
the government reduced tax on alkylate petrol by a total of
1.85 kr/litre from the 15th November 2002. This means that
the cost of a litre of alkylate petrol at the pump is just
a little higher than for 95 octane petrol.
So far the share of alkylate petrol sold to two-stroke outboard
engines hasn´t markedly grown. One reason is that the
Swedish oil companies hasn´t fulfilled their commitment
to significantly increase the offering of alkylate petrol
for sale from petrol pumps. The Swedish Minister of Environment
has put a pressure on the companies to fulfil a promise that
was given in connection with the tax reduction.
The project Grön Kemi is collaborating with "Miljösamverkan
i Väst" trying to enchance the offering and use
of alkylate petrol on the west coast of Sweden.