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Weapon Of Choice: Making Fertilizer-Based Explosives

by Glenn Hess
February 25, 2013 | A version of this story appeared in Volume 91, Issue 8

Makeshift bombs remain the leading cause of U.S. combat casualties in Afghanistan. The U.S. military says that about 85% of Afghan bombs use homemade explosives as their main charge.

Explosives can be made from a range of fertilizers, but it is far too easy to turn calcium ammonium nitrate into a bomb, says U.S. Army Lt. Gen. Michael D. Barbero, director of the Pentagon’s Joint Improvised Explosive Device (IED) Defeat Organization.

Fertilizer manufacturers began adding calcium carbonate to pure ammonium nitrate in the 1970s to make it less explosive. However, this highly valued and legally produced agricultural fertilizer is easily reprocessed by insurgents and used as the main charge, or explosive element, in IEDs.

According to the Pentagon’s counter-IED agency, insurgents routinely use two approaches to reprocess calcium ammonium nitrate before sensitizing it with a fuel. Ammonium nitrate is very soluble in water and can be separated from calcium carbonate, which is not soluble, by dissolving the fertilizer in hot water and decanting the concentrated ammonium nitrate solution. Excess water is evaporated, and the ammonium nitrate is dried and crushed.

Another processing method involves grinding the calcium ammonium nitrate into a fine powder without extracting the inert material.

The final product is packed into a plastic jug or box and then detonated with a blasting cap.

“The ubiquitous nature of these fertilizers, and their simple and easy processing into an explosive, makes this a dangerous and effective global threat,” Barbero says.

Since January 2011, more than 10,000 IED-related attacks have occurred in 112 countries, including Colombia, Pakistan, India, Syria, and the U.S., the Pentagon says.


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