Ground Fuels Quality

Most liquid fuel systems are vulnerable to microbiological contamination, with middle distillates like aviation kerosene, automotive and marine diesel, gas oil, and heating oils being particularly susceptible.

Currently, there are no widely accepted threshold values for microbial contamination in fuels. Establishing precise correlations between microorganism levels in fuel and their impact on operations and fuel quality is challenging. This difficulty arises because different types of microbes can have varying effects, and microbial contamination is not evenly distributed throughout fuel. Thus, detected microorganism levels can vary depending on where the sample is taken.

Initially sterile after refinery processes, fuel can become contaminated with low numbers of microorganism upon contact with water in distribution and supply chains. Microbial growth primarily occurs in water pockets, commonly found in poorly designed or maintained tanks and system low points. Water is essential for microbial growth, the microbes feed on nutrients in the fuel. Physical disturbance can disperse microbes from water into fuel. Under conducive conditions, these microbes may proliferate to levels that detrimentally affect fuel properties.

Microbial activity can lead to the production of surfactants, affecting fuel water separation and causing water entrainment, leading to failure of the “clear and Bright” visual appearance test due to “haze” caused by suspended water particles.

The formation of organic acids by microorganisms may increase fuel acidity, elevating the measured Total Acid Number of the fuel. Fuel from near the tank bottom may exhibit “blackening” due to corrosive sulphide produced by Sulphate Reducing Bacteria (SRB).  Silver and copper corrosivity tests may indicate failure to meet specifications due to the presence of sulphide. However, such impacts are typically observed in fuel with prolonged, significant microbial proliferation in water.

The most common impact on fuel quality is particulate contamination due to suspended microorganisms and their by-products. Fuel specification tests assessing particulate content, such as visual assessment (ASTM D4156), gravimetric assessment (e.g. IP 415), filterability (e.g. IP 387), or particulate counting (ISO 4406 cleanliness code), may be affected.

Suspended microbial particles can significantly impact fuel usability, causing severe filter clogging in end-user applications like rail, haulage, buses, and both fixed and portable power generation equipment. For further information on fuel contamination issues in the aviation and marine sectors, please refer to our Aviation and Marine pages under the Sectors We Serve section of this website.

How ECHA can help with Microbial Contamination in Ground Fuel 

• Analyse fuel samples from your facility, vehicle, or asset in our UK laboratory to evaluate microbiological contamination.
• Supply on-site microbial Test Kits, including ECHA’s MicrobMonitor®2, an internationally recognised industry-standard test (IP 613/ASTM D7978). This test can be utilised on-site or in the laboratory by non-microbiologists to detect microbiological contamination in diesel fuel.
• Conduct surveys of tanks and systems at your fuel storage facility or depot if there are concerns about microbiological contamination. Learn more about our Site Surveys.
• Provide guidance on remediation, control, monitoring strategies, and best practices. Find out more about our Consultancy Services.
• Offer comprehensive and customised training courses on microbiological contamination of diesel fuels and oils.