You may have seen reports in the press and on social media of incidents where agricultural and commercial machinery have suffered fuel starvation resulting in poor performance or ceased to operate caused by blocked filters; some HGVs have also been affected. This article offers advice on what to do to help prevent these issues from arising and how to treat such issues if they occur.
The Renewable Transport Fuel Obligation (RTFO), introduced in 2008, forms part of the government’s drive to fulfil climate change commitments, decarbonise the transport sector and increase the UK’s energy resilience. In broad terms the RTFO requires oil refineries and importers of fossil based road transport fuels and non-road mobile machinery (NRMM) fuels in the UK to add a percentage of fuel from renewable and sustainable sources. Bioethanol is added to petrol and biodiesel (or fatty acid methyl ester or FAME) to diesel and gas oil.
What has changed? Initially the requirement was to supply up to 3.5% renewable fuel into road fuels. This percentage has increased significantly in the last couple of years and the scope widened to includes NRMM fuel; this year the obligation increased to 9.18% and rises to 10.637% next year although the UK fuel specification currently limits the amount of FAME in diesel and gas oil to 7%.
Whilst the increase in the FAME content of diesel has been gradual over the last few years we believe that the increase in the FAME content of gas oil has been much more dramatic, rising from between 0-2% to 5-7%, this year.
How can increased FAME content cause contamination issues?
FAME has innate solvent properties which have a cleaning effect on fuel tanks causing the removal of particles and accumulated dirt from the tank and pipeline. FAME’s solvent properties can also have a corrosive effect on tank components, degrading rubber and plastic surfaces. Small particles (less than 10 microns) of tank debris are held in suspension within the fuel and can ultimately block the engine filters leading to an increase in fuel consumption and difficulties starting the vehicle. Unless a tank is new, or has been thoroughly cleaned, it is likely that a sudden increase in the FAME content of gas oil would cause this ‘cleaning’ effect to occur. This effect is unlikely to continue once the contents of the tank have been washed through although new deliveries can stir up debris which has settled at the bottom of the tank.
The methyl esters found in biodiesel have the ability to absorb considerable amounts of moisture and hold this water solution in the fuel. Fuel/water emulsion can affect performance and over time create suitable conditions for microbial growth. This in turn can lead to diesel bug (slime substance), yeasts and bacteria (algae) appearing within the fuel. This contamination will also lead to filter blockages and injector fouling resulting in reduced fuel flow and cause unexpected loss of power.
In cold weather, FAME, like fossil fuels, can result in waxing but it is then more likely to remain separated, leading to filter blocking issues even when the temperature increases.
What we have found so far…
The fuel meets British Standard.
Not everybody has been affected, in fact it is a small number of customers overall who have experienced problems. The initial ‘cleaning’ effect of FAME is probably the most common cause of problems. We do not fully understand all of the factors that might be involved but they include the age and condition of the storage tank and equipment, type of filters used, make and model of the machinery operated, and the temperature.
Instances of microbial activity found in customers’ tanks.
Some samples sent from customers’ tanks have shown instances of a presence of microbial activity (BUGS) which is a microorganism that can live, feed and proliferate in a fuel environment where there is water present. These instances have, so far, been relatively few and far between but are more likely to occur over time especially in older tanks, tanks with more dirt and debris and in warmer weather.
As the percentage of FAME in fuels goes up there is an increased risk of microbial growth and fuel tank contamination.
Our advice to customers is that proper maintenance of equipment and fuel storage tanks is now essential and the use of fuel additives is recommended. Keeping tanks as free as possible of condensation, regularly drained of water, and free from dirt are the minimum that will be required.
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