Protecting Land-Based Diesel Assets from Risks Associated with Biofuels

Greenhouse gases (GHG) are a global issue. As the planet warms, we need to find any way we can to lower carbon footprints. For the future, there are many projects working to find zero-carbon solutions using new energies, but, while we wait for these developments and the necessary infrastructure to support this energy transition, we need to find ways to reduce GHG, including emissions from current fuels.

More efficient machines, which use less fuel, and changes in fuel composition, incorporating more bio-friendly components, are two of the weapons in our “armory” for a greener world. The challenge we face, however, is that, although biofuels reduce emissions, they also pose increased risk of damage to valuable land-based assets.

Biofuel and biodiesel have been in existence for a long time. The sale of E10 petrol and B7 diesel became mandatory in the European Union (EU) in 2011. B7 diesel contains up to 7% bio component derived from renewable resources, which is generically referred to as Fatty Acid Methyl Ester (FAME). We understand the limitations of this fuel at lower temperatures; however, the addition of FAME also gives it a greater affinity to retain water. 

Water—Essential for Life … and Microbes

We already know that water will separate from fuel and steps to remove it are part of good fuel husbandry. However, with the introduction of FAME into its chemical composition, biofuel will retain water at greater concentrations, and the more FAME is added, the greater the potential for emulsified water.

At the refinery, fuel contains <200 ppm water content, but once exposed to the elements, B7 diesel can contain more than 500 ppm water. Increased percentages of FAME mean this number can go up to 1,500 ppm. Depending on fuel temperature, this can render the fuel hazy; an appearance that is not uncommon in the fuel supply chain when emulsified water is present.

The ingress of water comes from mechanisms such as condensation. As fuel is consumed and air takes its place in a tank, it brings moisture with it. Any swing in temperature can cause this moisture to condense to create free water. Both dissolved and free water will chemically react with FAME to form an emulsion at greater concentrations. 

Let’s be clear, the use of biodiesel is an essential part of GHG reduction and increasing FAME content is a vital part of our efforts to reduce the environmental impact of diesel fuel emissions while new energies are developed. However, the additional water potential that comes with biodiesel presents a problem. Fuel is likely to contain dormant microbial formations, such as spores. The presence of water and air creates an environment where microbes (yeast, filamentous fungi, or bacteria) can thrive.

As microbes multiply in the fuel, they can form a biomass layer consisting of billions of organisms. This biomass, which appears as a stringy, web-like substance, usually grey or brown in color, can block filters, increase injector wear, and even corrode tanks with the organic acid it produces. This was a problem even before the introduction of FAME, but the bio component in the fuel has exacerbated the issue. 

The Risks to Land-Based Assets

The increased percentage of FAME helps the environment but also increases the risk of microbial contamination. Additionally, technological advances in engine technology also make these precisely engineered machines more susceptible to the risks of microbial contamination. Engines have precise, higher internal pressure fuel nozzles, whose smaller orifices have a lower tolerance to sediments and particulate matter that might be generated by off-spec fuel. This requires better fuel management steps to ensure valuable equipment is not damaged and huge costs incurred.

A study by the Environmental Protection Agency (EPA) suggests that moderate or severe corrosion on metal components in underground storage tank (UST) systems storing diesel fuel in the U.S. could be a very common occurrence. The study found 83% of the inspected tanks had moderate or severe metal corrosion and reflects that the introduction of biodiesel in USTs has led to an increase in corrosion issues of around 40%–50%. This has a massive impact on downtime, including the need to replace system parts or even whole systems. A system will always fail at its weakest link, and although these may be relatively cheap parts, the impact on business could be huge.

The report goes on to say: “Prior to 2007, corrosion risks identified in tanks storing diesel fuels were generally thought to be limited to the bottom of tanks … The corrosion observed since 2007, however, may affect owners who have followed the same maintenance practices for years and had no corrosion issues.”

Although typical maintenance can include testing, monitoring via sensors, sampling, or fuel “polishing,” depending on the nature of the application, to avoid costly repairs and unnecessary tank cleaning, onsite testing offers an economical and quick way to determine levels of microbial activity in fuel. It presents a proactive solution and one that, with increasing percentage of FAME, will ensure users are ahead of any problems that may occur.

A research article published in Frontiers in Microbiology concluded: “A mixed microbial community of filamentous fungi and acid-producing bacteria were able to proliferate in B20 biodiesel storage tanks, cause fouling, degrade fuel by metabolizing the FAME, produce organic acids, and accelerate steel corrosion under biofilms attached to metal surfaces.”

Corrosion not only threatens day-to-day operations, but also presents a significant environmental risk if fuel escapes into the ground.

The EPA notes that biodiesel may contain glycerol as a by-product of the production process, and that “Metabolic consumption of glycerol by microbial populations could produce volatile organic acids such as propionic, lactic, or glyceric acids.” These acids were identified in the majority of water samples from the aqueous phase of fuels analyzed.

Onsite Testing Saves Time, Money, and Produces Accurate Results

A good onsite testing regime will help ensure contamination does not lead to corrosion or damage of systems. Understanding levels of contamination means maintenance actions, such as tank cleaning and adding biocide, can be tailored and optimized to avoid unnecessary costs.

Operators have two fundamental options when it comes to sampling to identify microbial contamination: sending fuel samples to laboratories or using onsite test kits. The frequency of testing can be honed according to microbial test results, observed trends, and operational experience. Microbes are living, dynamic organisms. This means that the microbial population can change while the sample is in transit, and, as such, laboratory testing requires careful storage and transportation of samples, and presents a higher risk that results may not be representative of the tank environment.

Onsite testing of land-based assets provides a quick, easy, and cost-effective alternative. Test kits based on antibodies, such as the FUELSTAT test kit from Conidia Bioscience, are a proven method for identifying microbes with the ability to degrade fuel and provide an accurate indication of contamination levels. Kits are low-cost, single-use, and testing is a simple process, requiring minimal training and no special handling. The straightforward nature of this approach means the task can be readily integrated into day-to-day operations with results available in a matter of minutes.


The introduction of biofuels with increased FAME content makes good sense for the environment, but we should not ignore the increased risk of microbial contamination and should adapt routine operations to ensure advanced corrosion and damage to system components does not threaten business continuity and profit.

To protect land-based assets, fuel management regimes should be updated to reflect the increased risk of microbial contamination from higher FAME content. Contamination can occur at any point along the fuel supply chain and simple, onsite testing may save thousands in repairs and help protect the environment from fuel leaks. 

Pierre Poitras is a technical consultant at Conidia Bioscience.

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