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Brewing a blast-less fertilizer

Preventing another Oklahoma City bombing

US Department of Homeland Security - Science and Technology

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IMAGE: Blast results from coated (top) and uncoated ammonium nitrate fertilizer-packed steel canisters. In fact, most of the blast seen in top photo is from the C4 plastic explosive used to... view more

Credit: Dr. Darrell Taulbee

Down in the green, rolling hills and farmlands around Lexington, Kentucky, Darrell Taulbee can be found mixing up a batch of his homegrown fertilizer. But he's not looking to grow a better Big Boy or distill a smoother bourbon, he tells us. Funded by the University of Kentucky and the Homeland Security's Science & Technology Directorate (S&T), Taulbee sets his sights on something far more sinister.

Darrell Taulbee putters with this stuff to make sure another Oklahoma bombing never happens again.

It was common fertilizer that Timothy McVeigh used to build the ferocious bomb that ripped into the Murrah Building, killing 167 innocent men, women, and especially children. Mixing ammonium nitrate with hate and fuel oil, McVeigh brought us a homegrown brand of terrorism and a raw grief from which we still reel.

Ammonium nitrate (AN) is a fertilizer used to create bumper crops. But, when combined with fuel oil (FO) it becomes ANFO, an explosive mixture of terrifying potential. The United States produces and imports millions of tons of it every year.

Taulbee is looking for ways to to reduce the destructive power of AN. He is eyeing coal combustion by-products--fly ash from electric power plants (120 million tons are produced yearly at coal-burning power plants)--to make AN less deadly. He coats AN pellets with fly-ash, packs them into metal canisters, and takes them deep into the Kentucky hills. There he blows them up.

Taulbee is methodical. With Tom Thurman, a retired bomb-scene investigator for the FBI now at Eastern Kentucky University, he learned that a mix of 20 percent coal ash to 80 percent AN keeps an explosion from burning all its fuel. This renders a blast far less violent.

"There are no commercially available options totally effective in preventing ammonium nitrate from being used as an explosive," Taulbee points out, "Coal ash won't stop the blast from initiating, but it will stop it from propagating." What's more, he adds, the ash is classified as non-toxic by the EPA and may have some beneficial effects for crops. It's inexpensive and coats easily onto AN particles, forming a hard outer layer difficult to remove.

Future research will include confirmation of Taulbee's results by the Bureau of Alcohol, Tobacco, Firearms, and Explosives, and the New Mexico Institute of Technology and/or the FBI. There will also be more extensive evaluations of the potential impacts on agriculture.

Mike Matthews oversees Taulbee's research for S&T. He says, "If Taulbee can eliminate much of the "McVeigh" factor in ammonium nitrate fertilizers, he'll go a long way in helping to contain the threat of these homegrown fertilizer bombs."

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