A huge explosion at a Fertiliser factory in West, Texas, has caused deaths, injuries and destruction to the town, near Waco. It's also drawn attention to the huge fertiliser industry. So, what is it, where is it - and how big is it?
Accidents and explosions
The explosion in West is only the latest in a long list of fatal incidents involving ammonium nitrate. The chemical compound is used both as a fertilizer and for explosive devices. Since 1921, at least 17 unintended explosions of ammonium nitrate including casualties have been recorded.
The most desastrous incident happened yesterday 66 years ago, when cargo ship Grandchamp exploded in the Port of Texas City, leaving 581 dead and 3500 injured. It is the deadliest industrial accident in the history of the United States.
Three other ammonium nitrate accidents have caused more than 100 deaths: The explosion of a BASF plant in Oppau, Germany in 1921 (561 dead); the explosion at a plant in Tessenderlo, Belgium in 1940 (189 dead); and the 2004 cargo train explosion of Ryongchŏn, North Korea that caused at least 160 deaths.
• List of major explosions
How big is the fertilizer industry?
The food shortage and consequent rise in world food prices has led to record demand for fertilizers around the world - and increasing trade in nitrogen, the main ingredient of many fertilizers.
Nitrogen imports chart Photograph: Guardian
Fertiliser production is big business - the United States exported $10.8bn-worth of them in 2012, around 9% of world consumption. And it imported another $13bn. That is equivalent to the annual GDP of North Korea.
The chart below shows where they go to and come from. Click the buttons below the heading to toggle between them.
Production facilities
Nearly every state in the US has at least one major fertilizer production facility located within it somewhere. This map, based on a list from industry body the Fertilizer Institute, shows where they are.
Why ammonia?
One of the most common ingredients found in fertilizer is ammonia - made out of nitrogen and hydrogen - which is created by sending natural gas, steam and air into a large container. The nitrogen and hydrogen is isolated before an electric current is sent through to turn it into ammonium, which is in this case was mixed with nitric acid to create the potentially explosive ammonium nitrate. This and all the other components of fertilizer have to then be whittled down and then mixed together before the final product is created.
Ammonium Nitrate is a strong oxidant - and is highly flammable in its raw state.
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