Sandia LabNews

Sandia offers world a fertilizer that fizzles as a bomb

Image of <p class="wp">BOMB-PROOFING FERTILIZER — Chemical engineer Vicki Chavez (6633) worked with now-retired Kevin Fleming to prove that iron sulfate mixed with ammonium nitrate could produce a non-detonable fertilizer. (Photo by Randy Montoya)</p>
BOMB-PROOFING FERTILIZER — Chemical engineer Vicki Chavez (6633) worked with now-retired Kevin Fleming to prove that iron sulfate mixed with ammonium nitrate could produce a non-detonable fertilizer. (Photo by Randy Montoya)

Ammonium nitrate is an essential fertilizer, high in nitrogen and a staple of the agricultural industry. But it has a dark side.

The raw ingredient in about 75 percent of the improvised explosive devices (IEDs) in Afghanistan is ammonium nitrate, according to US government reports. The fertilizer is illegal in Afghanistan but legal in neighboring Pakistan, where a quarter of the GDP and half the workforce depend on agriculture.

During Afghanistan’s 11-year war, IEDs have killed more American troops than any other weapon. About 1,900 troops were killed or wounded in IED attacks in 2012, 60 percent of American combat casualties. Ammonium nitrate was used in about 16,000 bombs in Afghanistan in 2012, up 200 percent since 2008, according to government reports.

US efforts to curb the flow of the fertilizer into Afghanistan through seizures, export controls, and diplomacy have had limited success.

Kevin Fleming, a Sandia optical engineer who also did counter-IED training for the military, took a different approach. He has developed a fertilizer formula as good as, if not better, than ammonium nitrate, but not detonable. And Kevin, with the support of Sandia officials, decided not to patent or license the formula, but to make it freely available in hopes of saving lives.

An Achilles Heel

“I looked at it differently,” says Kevin, who retired from the Labs in February. “I’ve been an organic gardener since I was 8. We had five acres in Las Cruces with the problems of calcareous soils that are very similar to those in the Middle East. I know something about commercial farming.”

He also knew the chemistry of IEDs from years of training soldiers how to deal with them.

Ammonium nitrate has an Achilles heel from a terrorist’s perspective. The ammonium ion is weakly attached to the nitrate ion. They hang onto each other, but the right chemical reaction can easily pull them apart. Kevin reasoned you could separate the ions by adding a compound they would rather cling to, called a metathesis reaction. “It would change into something else at the molecular level,” Kevin says.

He tried several materials including iron sulfate, a readily available compound that steel foundries throw away by the tons. When mixed with ammonium nitrate, the iron ion “grabs” the nitrate and the ammonium ion takes the sulfate ion. Iron sulfate becomes iron nitrate and ammonium nitrate becomes ammonium sulfate. This reaction occurs if people attempt to alter the fertilizer to make it detonable when mixed with a fuel.

“The ions would rather be with different partners,” Kevin says. “The iron looks at the ammonium nitrate and says, ‘Can I have your nitrate rather than my sulfate?’ and the ammonium nitrate says, ‘I like sulfate, so I’ll trade you.’”

Ammonium sulfate and iron nitrate are not detonable, even when mixed with a fuel. “It’s a different compound,” says Kevin, who completed work on the formula in late 2012. “At the chemical level it’s a great fertilizer but does not detonate.”

Chemical engineer Vicki Chavez (6633) ran a small-scale proof-of-concept of the reaction, and validated it. “We were able to prove that there was little to no ammonium nitrate left in the resulting process,” she says. “It was very cool. We looked at pure ammonium nitrate and pure ammonium sulfate. The resulting sample looked more like ammonium sulfate.”

Kevin says iron sulfate in fertilizer adds iron and acidifies soil. “It does good things for soil health. It takes alkaline soil and makes it more neutral, closer to an ideal pH level,” he says. “The closer you get a neutral pH, the more crops grow. Crop yield would improve significantly.

“And iron-containing fertilizer added to the soil would be taken up in crops and help fight anemia and other iron deficiencies in people who eat them.”

The soil in Afghanistan is alkaline with a high pH, and could benefit from an ammonium nitrate/iron sulfate fertilizer, Kevin says. “What they use now, ammonium nitrate with calcium carbonate — which makes soil more alkaline — doesn’t make sense,” he says.

Danger to soldiers

Sandia could have patented the formula but opted to waive ownership rights for humanitarian reasons.

“One of Sandia’s priorities is deploying the technologies that result from our research for the public good,” says Pete Atherton, senior manager of Industry Partnerships Dept. 7930. “In this case, we believe that making it freely accessible and disseminating it as widely as possible was the best way to accomplish this mission.”

Replacing ammonium nitrate with a non-detonable fertilizer in Afghanistan and other parts of the world will not happen overnight, Kevin says. Ammonium nitrate is produced in huge plants in many locations. “It’s easy to get in large quantities,” he says. “The sheer volume of ammonium nitrate is gigantic.”

But he says there are some thoughts on how to get the non-detonable formula into the marketplace. “We could give the formula to a neutral party and let them work with the Afghanis, Pakistanis, and others,” he says. “They could set up side-by-side demonstrations to see which fertilizer works better. Prove it to them gradually.”

Kevin says his sense of urgency in tackling the issue came from looking into the eyes of hundreds of soldiers he trained in anti-IED tactics. “Explosive Ordnance Disposal techs see a lot of IEDs, and about one third of them will die, be maimed, or injured by IEDs before getting through their tours, and most from ammonium nitrate-based explosives,” he says.

At a meeting last year in Crystal City, Va., Kevin sat next to an ex-Marine who had lost both legs trying to find IEDs. “He had a metal detector, but some bombs are chemically initiated with no metal parts. He stepped on a non-metal trigger and set off a blast that took off both legs. He became a double amputee in milliseconds. So when I sit next to him and see the aftermath of an IED, I have to think of any way possible to keep stuff like this from happening.”