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Recognizing diesel fuel algae

Posted by: Erik Bjornstad

The last 7-8 years have seen a dramatic rise across the nation in incidents of fuel storage tanks contaminated with "algae". We put that in quotes because we know it's not really "algae", but rather, other fuel microbes like mold, fungus and bacteria. It's commonly called algae because that's what people think it is (it's not really algae because algae is a microscopic plant organism, plants need light to grow, and fuel tanks are too dark to give them the light they need), so we roll with it. Whether it's really algae or it's bacteria or fungus, the problems are the same, no matter what you call it.

28jan10_-_biomass_bug.jpg.scaled.1000Problems? That's the subject of the day today. How to recognize if you've got an algae problem in your fuel tank.

There's a mountain of evidence and information that tells us what contributes to diesel fuel algae contaminating a tank. Loss of sulfur in the fuel (so there's nothing to keep it from growing) makes any free water in the tank a breeding ground for this fuel "algae". But how do you know if you've got a diesel fuel algae problem? Consider these warning signs that may point to a problem.

1. You stick the fuel tank and find any significant depth of water phase. Just as little as a quarter-inch layer of water at the bottom is plenty enough for microbes and diesel fuel algae to grow and thrive. And remember, depending on the size of the storage tank, just a quarter inch can represent tens of gallons of water in that tank.

2. You go through filters at a faster rate than normal. Diesel fuel algae plugs filters like crazy because the microbial bodies themselves get caught, as well as the black, slimy biomass matrix that they produce over the course of their lifecycle(s). Filters are also plugged when the activity of the microbes causes the fuel itself to lose storage quality and break down at a faster rate. Then you get filter plugging from asphaltenes and heavy end fuel components that have stratified and come out of solution. Any abnormal increase in filter plugging rate is a warning sign to check the tank for microbes.

3. You run a microbe test and it comes back positive. There are microbe test culture strips available that cost about $10 each. The test takes about 3-4 days to develop and will give you a qualitative (yes/no) rather than a quantitative (yes and this is how much) answer to your question.

4. Your fuel pH is lower than it should be. Algae in diesel fuel produce acids that gradually skew the fuel's pH towards an acidic environment. A pH of 7.0 is neutral, so adding acid to the fuel will decrease the pH number. A fuel pH of less than 5.8 indicates a serious problem and is strong evidence that there's a microbe problem going on in the tank. Finding this out requires a pH meter, of course, so if you have one, it's another bullet in the arsenal of evidence that you can collect to determine if you've got a diesel fuel algae problem.

And once you've confirmed that, you can take the next step to clearing the problem up.

Check out these other posts about "diesel fuel algae":

Protecting Stored Fuel Quality for Emergency Use

This post was published on April 16, 2015 and was updated on July 29, 2019.

Topics: Diesel, Fuel Storage, Fuel Distribution