Why Do We Use Explosive Fertilizer?

Isn’t there an alternative?

Officials from the Bureau of Alcohol, Tobacco, Firearms, and Explosives are searching for an unidentified man who has been trying to buy between 500 and 1,000 metric tons of ammonium nitrate fertilizer. When combined with fuel oil and a detonator, ammonium nitrate can become a powerful explosive—it’s what Oklahoma City bomber Timothy McVeigh used. ATF is concerned that the man they’re looking for, who has allegedly been using a Middle Eastern surname and phony credentials, has similarly destructive plans. If ammonium nitrate fertilizer is so dangerous, why does the agriculture industry keep using it?

Because ammonium nitrate is in many ways one of the best (and certainly one of the cheapest) sources of crop-nourishing nitrogen available. For starters, ammonium nitrate is inexpensive to manufacture. The process involves nothing more complicated than mixing together ammonia and nitric acid; the first batch of the stuff was synthesized way back in 1659 by German chemist Johann R. Glauber. A ton of ammonium nitrate fertilizer costs, on average, about $100 less than a ton of anhydrous ammonia fertilizer, one of the best alternatives.

Ammonium nitrate is also well-suited to bolstering certain types of crops. It’s quite effective with fruit trees, for example, providing more efficient nitrogen delivery than ammonium sulfate. Ammonium nitrate fertilizer is also popular for top-dressing pastures at midsummer since it evaporates more slowly than some competitors.

It’s not only farmers who prize ammonium nitrate, however. A low-density powder containing the chemical is vital to the construction industry, which considers it preferable to dynamite. Ironically, one of ammonium nitrate’s attributes is its stability—it won’t explode unless it comes in contact with both a hydrocarbon (such as fuel oil) and a detonation source. That’s not to say, of course, that tragedies haven’t occurred as the result of improper handling, perhaps most famously in Texas City, Texas, in 1947. A carelessly tossed cigarette sparked a fire aboard the S.S. Grandcamp, which was carrying a massive load of ammonium nitrate fertilizer. At least 567 people perished.

Both the government and the fertilizer industry are well aware that the fertilizer is coveted by terrorists, although regulation in the United States is light compared to Europe. Several European countries, including Germany and Ireland, ban pure ammonium nitrate fertilizer outright, mandating that it be mixed together with calcium carbonate. The mixture is more difficult for potential bomb-makers to use.

The European Union as a whole requires that ammonium nitrate fertilizers containing more than 28 percent nitrogen feature large, high-density granules, which are more difficult to saturate with fuel oil. However, it’s reported that bomb-makers can easily circumvent this measure by crushing up the fertilizer in an industrial-grade coffee grinder.

Only two states, South Carolina and Nevada, require purchasers of ammonium nitrate fertilizer to produce identification. But the Fertilizer Institute, an industry trade group, has asked vendors to request ID voluntarily and to report any suspicious buyers to a hot line. TFI’s pamphlet on the topic, titled “America’s Security Begins With You,” warns fertilizer salesmen to be wary of anyone paying with cash or who “avoids eye contact.”

Sen. Charles Schumer, D-N.Y., has proposed legislation that would make ID checks compulsory and require producers to add unique chemical tags to batches of fertilizer. These “taggants” would enable federal agents to better trace the source of any ammonium nitrate used in future terrorist attacks.

It’s also possible, especially if another ammonium nitrate bomb is exploded on American soil, that insurance companies will refuse to offer policies to fertilizer dealers carrying the product. Or perhaps manufacturers will simply bow to public safety concerns, as has already happened in Australia: Last spring, that nation’s largest fertilizer manufacturer voluntarily stopped selling all of its ammonium nitrate products. This was largely in response to concerns stemming from the 2002 Bali nightclub bombing, in which an ammonium nitrate device was detonated.

Next question?