What is ammonium nitrate, the chemical that exploded in Lebanon's Beirut?

For an industrial ammonium nitrate disaster to occur, a lot needs to go wrong. Tragically, this seems to have been the case in Beirut

The Lebanese capital Beirut was rocked on Tuesday evening local time by an explosion that has killed at least 78 people and injured thousands more.

The country’s prime minister Hassan Diab said the blast was caused by around 2,700 tonnes of ammonium nitrate stored near the city’s cargo port. Video footage appears to show a fire burning nearby before the blast.

 

Ammonium nitrate has the chemical formula NH4NO3. Produced as small porous pellets, or “prills”, it’s one of the world’s most widely used fertilisers.

It is also the main component