The ammonium nitrate that supposedly caused the Beirut explosions on Tuesday is a white, odorless salt used as the base for many nitrogenous fertilizers in granular form. According to the Lebanese prime minister, around 2,750 tons of ammonium nitrate were stored in the warehouse at the port of Beirut which exploded, causing dozens of deaths and unprecedented damage in the Lebanese capital.
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Ammonium nitrates are made up of fertilizers called ammonitrates, which farmers buy in large bags or in bulk. They are not combustible products: they are oxidizers, that is, they allow the combustion of another substance already on fire. " It's very difficult to burn it, " Jimmie Oxley, professor of chemistry at the University of Rhode Island, who herself has worked on the combustion of ammonium nitrate, told AFP. " It's not easy to detonate it ."
Detonation is only possible with contamination by an incompatible substance or an intense source of heat. Storage must therefore follow rules to isolate ammonium nitrate from flammable liquids (gasoline, oils, etc.), corrosive liquids, flammable solids or even substances that give off significant heat, among others prohibited, according to a sheet. technique of the French Ministry of Agriculture (in PDF).
Many tragedies around the world, accidental and criminal, have as their source ammonium nitrate. France retains in particular the tragic memory of the accident at the AZF chemical plant in Toulouse on September 21, 2001. 300 tons of ammonium nitrates suddenly exploded, causing the death of 31 people. The explosion was heard for up to 80 kilometers around.
Ammonium nitrate can also be used in the construction of explosive devices. The ANFO mixture is a highly explosive mixture composed of 94% ammonium nitrate and 6% kerosene, gasoline or diesel, the power of which is comparable to that of TNT.
But Professor Oxley qualifies by recalling that ammonium nitrate has become essential for agriculture and construction. “ We wouldn't have this modern world without explosives, and we couldn't feed today's people without ammonium nitrate fertilizers ,” she says. “ We need it, but you have to be really careful what you do with it. "