The impact of FAME in diesel

If you’re in the fuel industry, or store diesel to refuel your vehicles/machinery on site, then it’s likely you’ve heard about the increasing level of biodiesel and FAME content within diesel. Tougher renewable energy targets set by the European Renewable Energy Directive and the UK’s Renewable Transport Fuel Obligation are forcing suppliers to gradually increase the amount of biodiesel in their total fuel supply. In January of 2019 we saw the target percentage rise from 7.25% to 8.5%, which is further set to increase in January 2020 to 9.75%. But what does this increase in bio content mean for the industry and those using it? What problems can it cause and how do we overcome them? This is what we will answer here…

What is FAME and it’s knock on effects?

Biodiesel is a diesel replacement primarily made from recycled cooking oils, animal fats and plant oils. During the manufacturing process, Fatty Acid Methyl Esters (or FAME) are created that are consequently blended into the fuel.

The quality of European diesel fuel is specified by the EN 590 standard, which currently stipulates a FAME limit of 7%. Up until recently, we’ve seen the FAME content in diesel float around 5%, but now it appears we could be experiencing levels more around the maximum. Therefore, whilst the fuel being supplied into the market is still on spec, the two key characteristics of FAME are likely to be contributing to the noticeable change in your diesel.

  1. Sludge in fuel

    1. It is hygroscopic, which means it attracts and holds onto water. The problem associated with water content in fuel causing sludge, mould and bacteria to arise has been widely reported for years. More FAME, means more water, which means more nasty microbial growth.

  2. 2. It acts as a detergent, essentially cleaning any residual dirt or impurities from the tank walls and pipework it passes through, which ultimately end up in the fuel itself.  

Unfortunately, both of these characteristics mean that an increased level of bio content can result in an increased level of fuel contamination after it has been stored for a while. This is why tank owners may find their filters blocking quicker and them needing to be replaced a lot more regularly.

As well as an overall increase in bio content, it the type of FAME blended into the fuel can also be problematic. As biodiesel made from animal fat (tallow) has a higher level of saturates, it is more prone to waxing/gelling. It begins to crystallise at higher temperatures than bio made from vegetables oils, making your fuel appear cloudy and your filters clog. This higher cloud point makes the use of such biodiesel less suitable in the winter, which can further issues experienced when the cold months arise.

So, as a tank owner, what can you do?

Advice to limit FAME related issues

  • Filter Element

    Keep spare filter elements on site and change them as soon as you notice a drop in the flow rate. Replacing your blocked filter quickly reduces any tank downtime. Remember…A blocked filter is a filter that’s done its job! If a filter is blocked, then it’s full of contaminants. If it wasn't there, such contaminants would have entered the vehicle and caused some real damage. Better replacing the filter than the vehicle engine!

  • Before your next fuel delivery consider having your tank professionally cleaned. By ensuring that the internal tank walls and pipework are as free as possible from water, solid deposits, rust or mould, the detergent nature of the biodiesel will have less to act on.

  • Safeguard your tank against any water ingress by monitoring any leaks, replacing filler caps after deliveries and keep your tank topped up with regular fuel deliveries. Air holds moisture, so the fuller the tank, the less air there is inside the tank for moisture to be drawn out of.  

  • Keep an eye out for your fuel looking cloudy or the presence of sludge. These are important signs of contamination that need to be dealt with.

  • Don’t let fuel sit stagnant! Try and limit the storage time of your fuel as it becomes more susceptible to the problems associated with the water content in bio. However, if your tank isn't regularly used then a fuel recirculation unit could be installed to prevent the bacteria from settling and creating the nasty microbial sludge.

  • Avoid home remedies such as fungicides or microbiological killers that may do more harm in the long run. There may be some that end up working, but the dead bacteria growth will sink to the bottom of tank, build up and cause issues.

  • Try a filter specifically designed for biodiesel. Unlike filters that use a paper element, the Hydroglass filters use a high performance fibre glass element for the more challenging nature of biodiesel. It also benefits from a higher dirt holding capacity which can help to extend the element life.

If you’re noticing a change in the fuel you’ve had delivered, or if your customers have reported that they are experiencing this, then the above recommendations will help. For official notice and advice from UKIFDA; the UK and Ireland Fuel Distributors Association (formerly FPS) please click here

Download our whitepaper on FAME content in diesel here.

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