Ammonium nitrate: A fertilizer under scrutiny

STOCKHOLM: The storage of ammonium nitrate, the substance behind the deadly explosion in the port of Beirut on Tuesday, has come under increased regulation in recent years to avoid involvement of the ubiquitous product in accidents which, although rare, can be devastating.

Widely used and produced

The world’s annual production of ammonium nitrate is over 20 million tons for fertilizers alone, which means the amount that exploded in Beirut (2,700 tons) is made almost every hour. Storing hundreds or even thousands of tons in the same place is frequent, and a single farmer can easily use several tons a year. Analyst firm IHS says just over three quarters of the world’s supply goes to agriculture as a high-nitrogen fertilizer for crops.

The rest, in a higher and more volatile concentration, is used for explosives, particularly in mining and construction. The substance can be found in its natural state, particularly in Chile, where it used to be mined. But it has been synthesized since the early 20th century and is now almost exclusively produced in factories. Most agricultural use of the chemical-more than 70 percent-is in Europe and the former Soviet Union, according to the International Fertilizer Association.

Accidents rare, but terrible

There have been a few dozen accidents over the past century, with appalling consequences. One of the earliest, at a BASF plant in Oppau, Germany, resulted in 561 deaths in 1921. In 1947, in Texas City, an explosion of two ships in port carrying 3,500 tons killed 581 people. Nearly half of the North Korean city of Ryongchon, home to about 120,000 inhabitants, was damaged in 2004 when two trains, one carrying petrol and the other ammonium nitrate, collided.

The collision caused a massive explosion that killed 150 people, according to North Korea, or 161 people, according to relief organizations. According to a European Commission memo, accidents have been recorded at production sites, warehouses and during transport.