Microorganisms, it seems, can live in about anything — including diesel fuel.

That’s why it’s taken the city of Kokomo several months to — quite literally — work the “bugs” out of the city’s K-Fuel biodiesel program.

The biodiesel production program received national attention when it was announced in February, a green initiative aimed at turning used restaurant cooking oil into fuel for city trucks.

But the program ran into trouble shortly after the rollout, when a rash of gummed-up fuel filters parked numerous city vehicles.

By mid-June, city officials had ceased biodiesel production, and were seeking answers on what went wrong.

What they eventually discovered wasn’t pleasant.

A contractor ended up cleaning about 250 gallons of black sludge out of the city’s main diesel storage tank, a sludge created by microorganisms in the fuel.

Jack Harrison, assistant wastewater plant superintendent, said an Ohio laboratory confirmed the problem after analyzing samples of diesel fuel taken from several points — including the main diesel tank at the Kokomo Street Department garage.

After the lab samples determined the diesel tank was full of gunk, the next step was figuring out what to do, Harrison said.

In June, an attempt was made to clean the diesel in the main fuel tank, but simply filtering the fuel proved ineffective. At that point, city officials hadn’t realized microorganisms were causing the problem.

Once the lab results came back, the city found a different contractor.

The new contractor, city officials said, managed to solve the problem in two steps.

First, it killed all the bugs in the diesel tank with a fuel additive, similar to fuel-injector cleaner, Harrison said.

Second, after all of the dead microorganisms settled to the bottom, the contractors vacuumed the sludge out of the tank.

Randy Morris, city director of operations, said the city ceased K-Fuel production from about mid-June to mid-September.

Once city officials determined the problem seemed to be solved — and samples from the diesel tank came back a nice, clear yellow — K-Fuel production resumed.

For the past several weeks, about 15 diesel vehicles used at the city wastewater plant have been running on a 20 percent biodiesel mixture, wastewater plant superintendent Chris Cooper said.

No further problems have been reported, and the city is now ready to begin adding K-Fuel to the main diesel tank again, weather permitting.

Because biodiesel begins to gel at a higher temperature than regular diesel, city officials plan to carefully monitor how much K-Fuel they add to the diesel reserve during winter months.

Cooper anticipates eventually running a 5 percent mixture, while Harrison said he intends to monitor any gelling problems in cold weather.

Shutting down the program for the summer meant the city will fall considerably short of some of the goals set for the program when it was introduced.

City officials had hoped to produce up to 18,000 gallons per year, at a cost per gallon up to two-thirds less than the cost of purchasing regular diesel.

The city has managed to collect more than 13,000 gallons of cooking oil this year, Harrison said, but city officials didn’t have immediate figures on how much K-Fuel has actually been produced.

To make sure the microorganism problem doesn’t reappear, the city will have to continue using the fuel additive. In addition to killing any bugs in the biodiesel, it also removes water from the diesel tank, Harrison said.

That will add about $6,000 a year to production costs. City officials also haven’t accounted for the number of fuel filters which had to be replaced, or the number of man hours spent replacing them.

The city will also have to do a better job of filtering out animal fats in the cooking oil. The more animal fats survive the processing and end up in the final product, the more likely the final product is to breed microorganisms, Harrison said. The city is now forcing all of its raw feedstock through a 10 micron filter to take care of that problem, he added.

It wasn’t unanticipated that city officials would see fuel filter problems, once they started adding K-Fuel into the main diesel tank.

Because caustic soda is used to process the raw cooking oil, the finished biodiesel product was expected to have a detergent effect on city vehicles’ fuel tanks and engines.

Harrison said the K-Fuel staff thought the detergent effect was causing the fuel filter problems at first.

But the problems kept getting worse and worse, he said.

By June, he said, the gunk in the clogged fuel filters was so pronounced, “it looked like someone had smeared Vaseline all through [the filters].”

By then, the city had already paid one firm to filter the fuel stored in the main diesel tank, but the filtering didn’t work, Harrison said.

So the samples were taken, and sent to the lab. While the K-Fuel processing plant was shut down, city workers performed preventative maintenance on the unit.

Since returning to action about a month ago, it has produced almost 900 gallons of biodiesel, Morris said.

“It’s just something we had to learn,” Morris said. “It’s back up and running. It’s a good thing.”

• Scott Smith is a Kokomo Tribune staff writer. He may be reached at (765) 454-8569 or via e-mail at scott.smith@kokomotribune.com