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How common are fertilizer explosions?

Firefighters conduct a search and rescue of an apartment building destroyed Wednesday by an explosion at a fertilizer plant in West, Texas on Thursday. (AP Photo/LM Otero)

The explosion at a fertilizer plant in Waco, Texas Wednesday night was unique in the way that all disasters that claim unique human lives are, especially as it comes after the horrific bombings in Boston, making this a very bad week for the U.S.

But fertilizer explosions have happened before, and certainly aren't a dwindling threat given the booming petroleum-based fertilizer industry. (Most modern fertilizer is made of ammonium nitrate, which is highly flammable under the right conditions.) The Guardian, in lickety-split time, has produced an excellent data-based spread on its website that breaks down the multi-billion dollar fertilizer industry and lists pasts accidents, a chart sortable by fatality and by other factors.

Explosions of the accidental variety, The Guardian points out, include a 1947 accident in Texas in which the SS Grandcamp, a ship carrying ammonium nitrate and docked at the Texas City harbour,  violently blew up. That is still the worst industrial accident in U.S. history: it killed 581 people and injured 3,500. 

Other accidental explosions include the 2004 explosion of a cargo train in North Korea that killed at least 160 people and fertilizer plant explosions in Germany and Belgium.

But fertilizer is also a common ingredient in intentional bombings. The 1995 Oklahoma City bombing, an act of domestic terrorism that killed 168 people, involved a rented truck and bags of fertilizer. One of the worst episodes of violence during the Northern Irish "troubles" involved a fertilizer car bomb that exploded in the town of Omagh in 1998, killing 29 people.

Closer to home, the Toronto 18 terrorist plot would have involved fertilizer bombs had it been carried through -- two of the conspirators were unloading what they thought was ammonium nitrate when the RCMP descended in a planned sting, arresting the pair. (They later pled guilty to terrorism charges).

The Waco explosion has sent the fertilizer industry into PR overdrive, as this "talking points and facts" document provided on the website of The Fertilizer Institute, a Washington D.C.-based lobby group, can attest. They point out that fertilizer is relied on by farmers the world over (a problem deserving of another blog post, or perhaps a whole book, at a later date, though the TFI would never put it that way.)

As the document points out, petroleum-based fertilizer is made by combining nitrogen with hydrogen from natural gas. That creates "anhydrous ammonia," which is technically not a flammable substance on its own but will catch on fire with a "strong ignition" source, especially if combined with other flammable materials.

Global agriculture is so dependent on fertilizer products to maximize crop output that some academics speak of "peak fertilizer" rather than "peak oil." In other words, when we finally tap the world's finite supply of petroleum, our biggest problem will be creating food, not driving cars. 

Check out the Guardian's full data spreadsheet here.

READ MORE: Texas fertilizer plant explosion: Rescue crews search for survivors; up to 15 dead, 160 injured

Kate Allen is the Star's science and technology reporter. Find her on Twitter at @katecallen



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Not sure why the talking heads still bring anhydrous ammonia up when the post blast pictures clearly show the anhydrous tanks intact, while the building where the ammonium nitrate was stored is a crater. Doesn't lend to their credibility.

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