VIGILANCE and intelligence will always be the best weapons against terrorism. But it may possible to make it harder for terrorists to turn one readily available chemical into bombs. Ammonium nitrate, a widely used fertiliser, has been used in several IRA attacks, the World Trade Center bombing in New York in 1993, the Oklahoma City bombing in 1995 and the Bali bombing in 2002. The massive bomb found outside the US embassy in Karachi, Pakistan, on Monday also contained the chemical, according to some reports. Millions of tonnes of ammonium nitrate are produced each year for use as a fertiliser. Mining companies turn small quantities into an explosive by mixing the chemical with fuel oil. While it is not necessarily easy for would-be bombers to do this with fertiliser-grade ammonium nitrate, it is not impossible.
Now Speciality Fertilizer Products, a company based in Belton, Missouri, is patenting a water-soluble polymer coating for the fertiliser granules that repels fuel oil. The coating dissolves rapidly in soil, so it would not interfere with ammonium nitrate's main function as fertiliser. If it works and is widely adopted, the treatment could make it harder for terrorists to turn fertiliser-grade ammonium nitrate into bombs, and could also help prevent industrial accidents. "We have done infiltration tests that show that the oil does not get into the ammonium nitrate," says company founder Larry Sanders. That should at least reduce the force of any explosion that did occur. He is now sending the product to labs for tests. The cost of the coating would depend on how widely manufacturers adopt the technology, Sanders says. Not everyone is convinced, however. One expert, who asked not to be named, said that the polymer might react with ammonium nitrate under the high temperatures and intense pressures that follow the initial detonation, perhaps even providing additional energy for an explosion. But other groups are also working on ways of making ammonium nitrate less explosive.
"There's lot of research going on," says Jimmie Oxley, an explosives expert at the University of Rhode Island in Kingston. "It is way too sensitive to talk about." Most countries, including the US and Australia, do not regulate the sale of fertiliser-grade ammonium nitrate, but in the European Union it is already tightly restricted. "We are all aware of the sensitivities," says David Heather of the Agricultural Industries Confederation in Peterborough, UK. Anything sold as fertiliser must pass a detonation resistance test that determines how well the product resists an explosion. In the EU, fertiliser-grade ammonium nitrate is actually manufactured to higher standards than the explosive grade, with large, dense granules to prevent them absorbing fuel oil. Stabilisers are sometimes added to prevent the granules breaking down. Another approach is to mark fertilisers so that any bomb can at least be tracked back to its source.
Authentix of Dallas, Texas, says it can chemically tag any fertiliser during manufacturing. In the case of ammonium nitrate, molecules that contain different isotopes of nitrogen and hydrogen can be added in concentrations of parts per billion. "We can pick up traces of that marker in the explosive up to five kilometres away after an explosion," says Ian Eastwood at Authentix's UK office. Microtrace of Minneapolis, Minnesota, makes microscopic plastic barcodes that can be added to fertiliser. These barcodes can survive explosions and can uniquely identify up to 37 million products. However, while such technologies have long been available, they have yet to be widely adopted by fertiliser manufacturers.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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