(August 2007) Down in the green rolling hills and farmlands around Lexington, Kentucky, Darrell Taulbee can often be found mixing up a fresh batch of homegrown fertilizer. But he’s not looking to grow an heirloom tomato or distill a smoother bourbon. He has his sights set on something sinister.
With funding from the Science & Technology Directorate (S&T), Taulbee putters with the stuff to make sure that an Oklahoma City bombing never happens again.
It was common fertilizer—ammonium nitrate (AN)—that Timothy McVeigh used to build the ferocious bomb that ripped through the Murrah Federal Building in 1996, killing 168 men, women, and children. AN is used to create bumper crops, but when combined with hate and fuel oil, it becomes a lethal mix.
Taulbee is looking for ways to reduce AN’s destructive power. Right now, he’s eyeing coal combustion by-products—fly ash from electric power plants (where 120 million tons are produced yearly)—to make AN less deadly. He coats the fertilizer 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 the help of Tom Thurman, a retired FBI bomb-scene investigator now at Eastern Kentucky University, he has learned that a mix of 20% coal ash to 80% AN prevents such 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,” says Taulbee. “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 nontoxic by the Environmental Protection Agency and may have some beneficial effects for crops. It’s inexpensive and coats easily onto AN particles, forming a hard outer layer that is 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 the Directorate. “If Taulbee can eliminate much of the ‘McVeigh’ factor in ammonium nitrate,” says Matthews, “he’ll go a long way in helping to contain the threat of these homegrown fertilizer bombs.”