Protecting Land-based Diesel Assets in a Greener World

by Pierre Poitras (Conidia Bioscience/Biofuels Digest) ... how the increased percentage of biofuels can raise the cost of fuel as well as leave it susceptible to microbes. The analysis is based on the white paper Protecting equipment from microbial contamination when changing fuel chemistry

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 will separate from fuel, but the introduction of FAME into its chemical composition means it will retain water at greater concentrations. At the refinery, fuel contains <200 ppm water content but, once exposed to the elements, B7 diesel can contain over 500 ppm water. Typically, the greater the FAME content, the potential is greater for increased amount of emulsified water which can reach up to 1500 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. If a fuel tank is only half full, half of the tank contains air which, in turn, contains moisture. 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.

So why is this water such a problem? First, 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. 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.

Protecting assets

As we look to further increase the percentage of FAME to reduce environmental impact of fuels, the risk of microbial contamination also increases.

A study by the EPA¹ showed that the introduction of biodiesel in underground storage tanks (UST) has led to an increase in corrosion issues of around 40-50%.

Recommended maintenance can include testing, monitoring via sensors, sampling, or fuel “polishing”, depending on the nature of the application.

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.”

Why test on site?

It is good practice to remove as much water as possible from fuel supplies, but a sound testing regime will also help ensure contamination does not lead to corrosion or damage of systems.

As the chemical composition of fuel changes, however, we need to recognize the increased risk of microbial contamination and adapt routine operations to ensure advanced corrosion and damage to system components does not threaten business continuity and profit.

Although operators may have previously had no issues with microbial contamination, fuel management procedures should be updated to protect land-based assets. Contamination can occur throughout the fuel supply chain and simple, onsite testing may save thousands in repairs and help protect the environment from fuel leaks.