In general there are two ways of reducing SO2-emissions, using fuel with less sulphur content or clean the exhaust gases. In line with our strategy Wallenius is focusing on upstream solutions, i.e. the fuel based option.
Different qualities of fuel oil
There are several qualities of fuel oil for example normal heavy fuel oil, low sulphur heavy fuel oil and distillates. The cleaner distillates are significantly more expensive than the heavy fuel oils.
Test with clean fuel - Marine Diesel Oil
During a period of four years, from January 1998 to December 2001, m/v TURANDOT was operated on Marine Diesel Oil (MDO). As a result, the SO2 emissions were reduced by more than 75 per cent. The SO2-emissions of m/v TURANDOT was equivalent to about 300 tonnes of sulphur while her sister vessels m/v TITUS and m/v DON JUAN emitted SO2 corresponding to 1,200 tonnes and 1,400 tonnes of sulphur respectively. Apart from lower sulphur content, it was noted that a dramatic reduction of ash, carbon residues, aluminium, silicone and other particles also occured. The amount of those unwanted residues is zero, or non-measurable, according to the normal fuel test procedures. The emissions of ash from the vessels operating on HFO are about 4—5 tonnes per year.
The heat value of MDO is around 5 per cent higher than that of HFO, resulting in reduced fuel consumption. Additionally, no pre-heating is necessary and therefore less oil is used.
When operating on clean fuel like MDO, the cleaning and maintenance work of all fuel-related systems and components are reduced. Comparing m/v TURANDOT to m/v TITUS and m/v DON JUAN saw a reduced work level for the engine crew by about 65 per cent and for the second engineer by about 75 per cent. The time required for overhaul of parts was reduced by about two thirds of the time thanks to less and easier cleaning. The quantity of spare parts required is also reduced.
Fairway fees in Sweden are reduced when a cargo vessel is operating on fuel with less than 1.0 per cent sulphur content. With low sulphur fuel, the total base number (TBN) of the cylinder oil can be lowered, becoming less expensive. This was tested on m/v TURANDOT where four cylinders were lubricated with TBN 70 and four cylinders with TBN 50. The volume of sludge was expected to be reduced by more than 50 per cent thanks to the smaller amount of cat fines, aluminium and silicone residuals and other particles. However, the total volume is depending on how sludge and waste oil are treated onboard. It has also become evident that MDO bunker can create large volumes of sludge due to problems with quality. These problems are probably related to blending products in order to meet the low sulphur specification.
The aim of the test was to establish what savings could be achieved and if they could balance out the higher price of the fuel. Unfortunately they could not.
Evaluation of low sulphur heavy fuel oil
A new test started, the question was: is it possible to run our vessels on LSHFO? Today, this seems like a strange question to ask but in those days it was said that the sulphur content in the fuel was needed to lubricate the engine. We therefore tested running one of our vessels on LSHFO with sulphur content below one per cent.
This test was successful and we implemented a procedure of taking delivery of LSHFO whenever possible. It started with deliveries in Europe but our commercial carrier Wallenius Wilhelmsen Logistics later expanded the contracts to also cover deliveries in other locations, such as Singapore. The result in average sulphur content for an ocean going service was at a record low level: 1.16 per cent for our Swedish flagged vessels. Since 2004 we have been running our vessels on fuel with sulphur content well below 1,5%.
When running on lower sulphur fuel, cylinder oil with a lower TBN can be used because less neutralisation of sulphuric acid is needed. There has been lots of speculation on problems when shifting from a bunker with higher to lower sulphur content and vice versa because of the possibility of an excess or a deficit of neutralising agents. We have seen no such problems so far. Both m/v ELEKTRA and m/v BOHEME ran on TBN 70 whether they received LSHFO or not while m/v OTELLO was operated on TBN 40 with good results.
Auxiliary engines on MDO
Since 1999, our policy has been to run the auxiliary engines on Marine Diesel Oil (MDO) or Marine Gas Oil (MGO) with a maximum sulphur content of 0.2 per cent. The experience from that has been very positive.
Maintenance has been minimised, and the time between overhauls and total lifetime have both been extended. The substantial reduction in soot particle levels is one of the main reasons for using this fuel when the vessel is at berth and large numbers of people, at the quaysidenand in the surrounding areas, are exposed to its exhaust fumes.
Is LNG the future fuel?
Liquified Natural Gas, LNG, is practically free from sulphur. Recently we have been exploring the possibilities to convert our old vessels to dual fuel engines enabeling us to run on LNG when for example in Emission Controlled Areas. The study showed really promising results. The technology is there and it gives significant reduction in environmental impact; practicably no suphur, 80% NOx reduction and some 20% CO2 reduction, however the infrastructure for the LNG supply is not yet developed and the installation costs are very high.
LNG is however likely to develope as a marine fuel during the near future and will hopefully be bridging the gap to bio gas.
Read about our results and statistics within sulphur emissions