Sustainable sea-going traffic

Waxholmsbolaget is one the largest maritime stakeholders within the County of Stockholm. With more than 4 million passengers and 7,000 tons of goods each year we are that vital nerve that is required to provide a living archipelago, where people can work and live and where thousands of tourists and summer guests can relax.


We and our owner's, Stockholm's County Council, want this to continue in the future. Therefore we have been commissioned to operate and develop Waxholmsbolaget in the long-term and sustainably, with great consideration for the sensitive environment of the archipelago.

Better fuel, cleaner air and fewer waves.

This not only gives us a special responsibility, but also the strength and chance to lead and direct environmental adaptation onwards. During the approximately 15 years we have focused on environmental issues, we have been able e.g. to test, research and invest in new technology, alternative fuels and operational techniques. This is to improve our own activities, but also to inspire and put the pressure on our suppliers and collaborating partners. There are primarily three areas that we are anxious to work with: reducing the use of fossil fuels, reducing emissions into the air and finally, reducing excess waves that may damage the surroundings.

Reducing the use of fossil fuels

Today – eco-diesel, class 1

All our ships operate on diesel, Eco-class 1. A few years ago we also tried using synthetic diesel. It is manufactured from natural gas and was very well adapted to combustion in our engines, resulting in almost 100% combustion with cleaner exhaust and less smoke. The experiment continued for one year and the synthetic diesel turned out to be perfect as fuel for our ships. However, it was too expensive – and it is still a product of fossil raw materials which we are striving to resist.

Tomorrow – diesel from renewable raw materials

Since both ethanol and biogas are too explosive to be handled on ships, fuel and renewable raw materials are scarce within shipping. To hasten development of sustainable alternatives, we have an active collaboration with both oil companies and engine manufacturers. Together, we test and develop different types of fuels in efforts to find tomorrow's fuel which is manufactured from renewable raw materials and is adapted to ships.

Minimum additions of carbon dioxide

So far, diesel from renewable raw materials is almost twice as expensive as the fossil diesel. However, both the manufacturing methods and the possibility of using different raw materials are being developed continuously. We therefore hope that we will soon be able to run all our ships with renewable diesel. As with all combustion, carbon dioxide is certainly produced in this method as well, however since the plants that the renewable diesel is manufactured from bind carbon dioxide when they are cultivated, our net contribution to the atmosphere will be reduced by 70–80 %.

Reducing emissions into the air

Modern engine technology reduces emissions

Alongside the work in finding suitable fuel, the upgrading of engine technology is ongoing as well. The requirements are high when we build anew and renovate both in our own fleet and towards our contactors. Using new engines with electronic engine control and modern injection systems, we strive to achieve more efficient combustion and use the fuel to its maximum.

New methods of cleaning exhaust

In order to clean our exhaust, we have also installed catalysers in all our ships. But we are also testing other post-treatment techniques to minimise the amounts of nitrogen, soot and dirt. A few examples are selective catalytic purification and a new particle filter that has been developed especially for ships, just like EGR (Exhaust Gas Recirculation) where some of the exhaust gases are returned for combustion in order to reduce nitric oxide emissions.

Economical driving saves time and money

A smooth and adapted driving technique reduces emissions and saves fuel, even when at sea. For this reason, we started the project Economical driving at sea in 2004 together with the Swedish Environmental Protection Agency (Naturvårdsverket). All our captains are involved and the ships have been equipped with fuel computers. Here, we could immediately see how the fuel consumption was affected by driving techniques, different maneuvers, cruising speeds and acceleration. The results were clear-cut - a speed increase means an increase in fuel consumption, multiplied by three! By reducing the top speed and adjusting our driving to a smoother pace, we could reduce our fuel consumption by 10 %. This will result in reduced emissions and less risk of breakdowns, while we save money. Combined with our new navigation system, we can also trim our timetables. With exact information on how long it takes to complete a run, it will be easier to adjust the speed and arrive in time.

Smaller wash from our ships

Economical driving and new trim tabs

Backwash is perhaps not an environmental issue in a traditional sense. However, it is an effect from our activities that affect the surroundings and is therefore something we must work to minimise. One example is the new economical driving technique, which in addition to reducing the fuel consumption also has a positive effect on wave building.

Since the spring of 2007, we have been collaborating with the KTH Royal Institute of Technology and the company Humphree in developing  interceptors for our ships. This is a kind of vertical trim tab which is attached alongside the stern, a few centimeters under the waterline. Here, they help to increase the pressure on the bottom of the hull, which lifts the ship up into a better trim angle.

Tests have been performed on some of our fastest ships with very good results. The height of the backwash was reduced by as much as 20 %. The fuel consumption was also reduced by a further 5 % while the comfort onboard increased. The plan now is to equip all our fast-moving ships with interceptors with GPS-control. This means that they will automatically adjust their position according to speed, so that the ship will always lie optimally in the water and thereby cause the least possible wash.