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Posted on: 18/06/2018

RTFO and FAME advice sheet

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The use of biodiesel is driven by both European and UK legislation. In Europe, this is known as the EU Renewable Energy Directive and is supported by UK legislation (generated by the Energy Act of 2004) known as the Renewable Fuel Transport Obligation (RTFO) which since 2008 has set the volume target for renewable fuels in the UK supply chain. In April 2018, the percentage of fuels derived from renewable sources increased to 7.25%.  From January 1st, 2019 this percentage will rise to 8.50% and continue to increase up to 12.40% by 2032.

Suppliers have obligations to meet these targets, but how they meet these obligations is up to them (increasing ethanol in petrol, purchasing tickets to cover the shortfall - the more expensive option – or adding FAME to sulphur free gasoil also known as SFGO).

The British Standard for non-road diesel (known as BS2869) was revised in 2006 to allow the addition of FAME to both classes of middle distillate fuel, however this was rarely realised.  Then the EU Fuel Quality Directive was implemented in the UK on the 14 January 2011 introducing changes to the composition of SFGO.   Fuels intended for use in non-road mobile machinery (NRMM e.g. tractors) will have a sulphur content of 10ppm.

With the new RTFO changes, all our suppliers have told us that they cannot now guarantee that their SFGO will be FAME free. Also because many distribution terminals only have facilities to handle and store three grades of distillate fuel so it is possible that road diesel (including FAME) will now be marked and supplied for NRMM use.

What is FAME?

Biodiesel is a diesel replacement fuel, which in the UK is manufactured mostly from feedstocks of recycled cooking oils but may also be made of a variety of blends of other renewable and recyclable material including tallow (animal) fats and plant oils. The biodiesel manufacturing process converts these oils and fats into long chain molecules. These molecules are also referred to as Fatty Acid Methyl Esters and are more commonly referred to as “FAME”. FAME has been blended into UK road fuel since 2004 in levels up to 7%.

FAME is a powerful solvent, with good detergency properties. Unlike diesel, FAME is “hydroscopic” which means it attracts and holds onto water.

Oil Samples

Potential Problems

There is considerable experience within the automotive sector and oil industry regarding the use of FAME in diesel and much of this will have some relevance to SFGO. The main issues to be aware of include: -

•            Material incompatibility (many common rubbers, plastics and surface coatings will degrade from contact with fuels containing FAME) 

•            Residual deposits causing clogged filters

•            Water uptake - with enhanced potential for mould, bacteria and algae growth

•            Fuel stability (may degrade over time by oxidation and hydrolysis)

•            Cold flow waxing and precipitation problems   


Ideally, before taking a delivery of any bio fuel, the tank should be cleaned internally. Solid deposits, mould growth and water build up or ingress should be removed as efficiently as possible. This may require specialist tank cleaning service.

If it is not possible to undertake a full clean before receipt of the first delivery, then it is advised that a thorough inspection of the tank’s condition and suitability is undertaken and recorded. This should include the construction material(s), age, condition and appearance of the tank, any damaged areas and surface coating(s). Any obvious deficiencies or concerns should be remedied as a matter of priority.

Delivery Tanker at plant nursery 3

Ongoing Housekeeping

There is a risk of microbial growth for all distillate fuels, but the biodegradable nature of biofuel blends is thought to heighten this risk. Therefore, more regular tank checks will be required, (due to FAME’s strong detergency, solvent and hydroscopic properties) compared with those of purely hydrocarbon fuels.

Tanks should be examined for signs of degradation in structure, material or coating. Prompt and appropriate removal or remedial action must be taken for any water, dirt, mould or growth present in the tank. 

Note: tanks that don't already have drain points for removing water are likely to need modification. Examine sight gauges on older fuel storage tanks for signs of leakage and replace any leaking seals.

Filters should be examined at frequent intervals and fuel filters replaced after two or three deliveries.

Pipework, seals, pumps and other components must be checked continually for signs of actual, or potential, oil leaks and, if found, remedial work and/or material replacement undertaken immediately.

If you are having tanks serviced before you receive the new fuel it would be advisable to replace fuel seals as a one-off, precautionary exercise.

Most NRMM engines, maintained in compliance with manufacturer’s service guidelines, are fully compatible with fuel containing FAME in the proportion found in fuel. However, some fuel system components on older engines, including seals and pipes, may not be compatible.


Water is possibly the biggest problem with regards to SFGO containing biodiesel. Therefore, all effort must be made to safeguard any tanks or containers from water ingress by rain or moisture in the air as well as regularly draining any water off. Additionally, keeping a tank brim-full ensures that there is little air left in a tank to draw moisture out of.  Once in a fuel, water brings about increased corrosion of equipment and worse, allows bacteria to breed.

To reduce these risks, many industry webpages suggest that biodiesel (and therefore bio SFGO) has a limited shelf life and some suggest it is best to avoid storing FAME blends for more than six months. 

Things to consider:

•            Ideally, undertake a full, professional clean of your tank ahead of the first delivery of a bio blend.

•            At least initiate an immediate check on the tank checking condition and suitability. This should include the construction material, pipework and seals. Any obvious deficiency or damage must be remedied.

•            Subsequently check the tanks often and have a regular maintenance programme.

•            Keep the fuel clean and dry and top up the tank to reduce air which can draw moisture.

•            If you find sediment or bacterial growth seek professional help.

•            Home remedies such as fungicides or microbiological killers may do more harm in the long run. Those that do work may kill the bacteria but the dead growth on the bottom of tank can also build up and cause issues.

•            Buy your fuel direct from a reputable distributor.

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