Preventing microbial growth in diesel fuel

I recently encountered a 10,000-gallon diesel storage tank that had been in service for decades. A ladder inspection on top of the tank revealed a defective vent/breather gasket that let water gradually seep inside.

Also, there was no bottom drain to remove the accumulated water. It was no wonder that this farmer’s combine fuel filter plugged shortly after the beginning of harvest. As expected, the fuel filter was black and tested high for microbes.

The best way to control fuel-borne microbes is to prevent or eliminate the free water that builds up in storage tanks. When fuel moves in and out of the tank, moist air and other contaminants are introduced inside.

As ambient air temperatures cool, water condenses on the inside of the tank and falls into the fuel and ultimately to the bottom of the tank. Microbes are typically found at the water-fuel interface -- an environment where they can rapidly grow and multiply.

Reports of filters plugged with microbial growth are increasing. As it turns out, today’s ultra-low-sulfur diesel (ULSD) has a higher affinity to water than traditional, high-sulfur fuels. Some also believe that the higher levels of sulfur that once were present in diesel fuel acted as a natural biocide.

Combines and other diesel-powered machines that are stored away for long periods with empty fuel tanks are likely to accumulate condensation over time and develop favorable conditions for microbial growth. While even full tanks can contain microbial growth, filling tanks with fuel reduces the amount of condensation that occurs and ultimately results in fewer problems.

If you suspect you have microbes in your storage tank, solutions to the problem may be as close as members of local FS cooperative’s energy team. They can test your fuel with a Bug Eye test kit and recommend biocide treatment if microbes exist at or above treat rate thresholds.

Another product, BUG OUT Sticks, provides ongoing protection from microbial growth and won’t activate until the presence of water is detected. After effective treatment, it is recommended that fuel filters be changed frequently as dead micro-organisms continue to be strained from your fuel.

Managing fuel quality may seem foreign if you haven’t had to do it until now. But if you want your equipment to be ready when you are, paying attention to these details can pay big dividends.
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Ken Reichert is GROWMARK’s refined and renewable fuels sales manager. His e-mail address is kreichert@growmark.com.