Marine Biodiesel- Does it Affect You?
Until recently that would have been a difficult question to answer, in fact we could almost certainly have said that if you own a seagoing vessel the answer would be ‘No’. But things are changing, although the law still only applies to inland waterways, fuel wholesalers are increasingly finding that they cannot keep stocks of two types of marine diesel. For this reason many coastal marinas now stock only biodiesel (and have no obligation to advertise the fact).
The informative article below should answer all your questions. Although originally aimed at inland waterways it now applies equally to all pleasure craft owners.
Marine Biodiesel- Your Questions Answered
(Reproduced with kind permission of Dave White)
The fuels used in inland waterways craft are changing. EU Directive 2009/30/EC requires that the fuel used for inland waterways craft and boats 'not at sea' must contain no more" than ten milligrams of sulphur per Kg of fuel”, generally known as ULSD. At the same time 'biodiesel' is being introduced which will contain up to seven percent biologically produced diesel, or FAME.
These two changes present some important issues for inland waterways craft users. For a long time there have been problems with microbiological spoilage of stored diesel on boats. This is caused by diesel bug, the generic name given to a group of organisms that enjoy growing in fuel tanks. These organisms can include yeasts, moulds and bacteria and they often develop at the interface of water and fuel. This occurs when water is held in suspension within the fuel, or more commonly in the water bottoms in the fuel tank where condensation ends up. These organisms prefer not to be disturbed while replicating, so boats not used for a few weeks at a time are the ideal environment for them.
Symptoms that occur from spoiled fuel include a slime formation in the filters, poor starting, smoking and often a lack of power or inability to achieve full revs. The sludge that forms from these organisms also tends to be acid and can cause corrosion problems within the fuel system. There are also sulphate reducing bacteria that thrive where there is no oxygen. Their presence can be recognised by a bad egg smell and the by-product is sulphuric acid which has been seen to eat through half inch thick steel plate.
When biodiesel is blended, fatty acid methyl esters (FAME) are added to the mineral diesel and it would appear that micro-organisms love FAME. The fuel supply industry has added control measures and generally throughout the supply chain there does not appear to have been a problem so far.
Once the fuel is in your tank, however, it is up to you to take care of it. If the fuel is no longer being disturbed the FAME attracts moisture which allows the organisms to grow. Add condensation which forms water bottoms and the bugs have all they need for proliferation: water and carbon forms that they can break down.
There are precautions you can take to prevent the occurrence of these problems. Whenever possible keep your tank full to eliminate condensation. Be aware of what fuel you are buyng. Ask the supplier for details. Try to use fuel from a source that is regularly turned over.
You can also use additives and biocides. These can claim to solve the problem in a variety of ways. Some claim they can break down the size of the organisms so that they pass through filters or that they remove the water that is required for organisms to grow. There has been test work done comparing all of these approaches but the biocidal route has been shown to be the most effective. Biocides should be used with due care but should not be perceived as particularly harmful or dangerous. Many foods, paints, shampoos etc contain biocides as preservatives and so at the level we need to use it these additives are not generally damaging. Often the preventative level is only 50ppm( 0.005%) and this of course is burnt along with the fuel itself. This is probably the safest route and in the long term this actually prevents overuse of the biocide. This is because it eliminates spoiled fuel and so there is no requirement for dumping of unusable fuel and shock dosing of biocide.
Overuse of antibiotics has led to the formation of so called superbugs. It should be noted that these are resistant to antibiotics within the human body. Some biocides work better with some organisms than others so a choice has to be made. There does not appear to be evidence in the field of resistance to biocides happening, but if it did then the suppliers would introduce alternatives to rotate. The use of FAME has also given some side effects. FAME is an excellent solvent and can start to break up the sludge found in the bottom of most fuel tanks. If released this sludge can block filters. If you can have your tank cleaned, then do so. Ideally, water in the tank should be removed regularly either using a drain plug or through the filter separator. Keep turning over the fuel on a regular basis, ie use your boat.
Most modern diesel systems should not have a problem with parts and FAME but older engines might be affected. When having older engines serviced it would be advisable to check with your engineer that your fuel hoses will tolerate biodiesel and that all seals are compatible. It is advisable, as the new fuel is introduced to change your filters more often to start with. It has also been shown that the use of RME (rapeseed methyl ester) and FAME has led to fuel system deposits being formed. These in turn cause power loss, injector plugging, higher fuel consumption and higher emissions. This can also be counteracted by the use of aftermarket additives. You should also remember that diesel engines like to run hot, so wherever possible keep them under load when running. This is not always possible on the inland waterways of course where boat speeds are severely limited, and so this side effect of RME and FAME is likely to be more prevalent.
In summary, in the interests of global warming we will all have to take more care of our fuel and its use. As fuel gets more scarce and expensive it should be used as efficiently and in as environmentally a way as possible.