Making fertilizer safer

Published 5 July 2007

Timothy McVeigh showed how destructive common ferilizers can be; University of Kentucky researcher is trying to make them safer

In 1995 Timothy McVeigh deminstrated how deadly common agricultural fertilizers can be when used as a weapon. Now, Darrell Taulbee, a University of Kentucky researcher, is conducting test to see whether bombs made from fertilizer with ammonium nitrate, the same substance used in the Oklahoma City bombing, can be made less destructrive by coating the ammonium nitrate with coal ash, thus diluting the material and lessening the explosions. Taulbee thinks his method could stop the substance from being used for bombs and keep the fertilizer in farmers’ hands.

Lexington Herald Leader’s Sean Rose reports that following the Oklahoma City bombing, Taulbee thought of adding coal ash, a byproduct of coal-burning electric plants, to dilute the explosive chemical. He had to wait for funds from the National Institute of Hometown Security in Somerset, a contractor for DHS, and tested his theory over the past two years. He found that a mix of 20 percent coal ash to 80 percent of ammonium nitrate would keep an explosion from burning through all its fuel, making the blast far weaker than unmixed fertilizer. Greater concentrations of ash further weaken the explosion’s strength.

Two of the biggest advantages of coal ash over other dilution substances are that it’s non-toxic and cheap. Mass quantities and near-zero demand for it mean one ton of coal ash can be bought for about $5. Keeping the cost down is important because Taulbee wants the fertilizer to remain affordable and still be beneficial to crops. True, some heavy metals that could be in coal ash could damage crops, but at just a 20 percent mix, it would be something to monitor rather than worry about, said Wilbur Frye, executive director of the office of consumer and environmental protection in the Kentucky Department of Agriculture.

Ammonium nitrate supplies crops with nitrogen, an essential chemical in farming. It is applied topically rather than being injected into the ground. It has the advantage over other fertilizers of not losing nitrogen when exposed to air for longer periods of time. Urea is another common fertilizer. It has a greater concentration of nitrogen but is also more expensive, between $450 and $500 a ton, compared with ammonium nitrate at $350 to $400 a ton. Urea also needs rain to carry the nitrogen to the plant and loses its nitrogen if applied during dry spells. Liquid nitrogen fertilizers are another fertilizer option. Liquid nitrogen costs $330 a ton but requires more expensive equipment to inject it into the ground.

Ammonium nitrate has been facing problems since 1995. Fewer manufacturers make it now because of liability reasons, so safer fertilizer could mean more manufacturers might make it again. Adding coal ash could also save the fertilizer from being banned altogether by the federal government, something DHS has been considering for a while now.

Investors note: Taulbee is now looking for additional funding for further research. He is planing to follow up on testing the agricultural side, making sure the fertilizer will still benefit crops and turn more extensive blast testing over to federal agencies like the Bureau of Alcohol, Tobacco, Firearms and Explosives. “It has the potential of worldwide application,” said Ewell Balltrip, president of the Somerset, Kentucky-based National Institute for Hometown Security.