Thick smoke billows from the site where a massive explosion rocked Beirut's port Marwan Naamani / dpa Marwan Naamani / dpa / dpa

LEBANESE AUTHORITIES HAVE said ammonium nitrate was the cause of yesterday’s two major explosions that ripped through Beirut’s port, killing at least 100 people and injuring thousands. 

The second blast sent an enormous orange fireball into the sky, immediately followed by a shockwave that flattened the port and shattered windows across the city.

The explosions — which were heard in Nicosia, 240 kilometres away in Cyprus — were logged by seismologists, registering as the equivalent of a 3.3-magnitude earthquake.

Prime Minister Hassan Diab has said 2,750 tonnes of the agricultural fertiliser ammonium nitrate that had been stored for years in a portside warehouse had blown up, sparking “a disaster in every sense of the word”.

“What happened today will not pass without accountability,” said Diab. “Those responsible for this catastrophe will pay the price.”

So, what exactly is ammonium nitrate? 

Ammonium nitrate is an odourless crystalline substance commonly used as a fertiliser that has been the cause of numerous industrial explosions over the decades. 

These include notably at a Texas fertiliser plant in 2013 that killed 15 and was ruled deliberate, and another at a chemical plant in Toulouse, France in 2001 that killed 31 people but was accidental.

When combined with fuel oils, ammonium nitrate creates a potent explosive widely used by the construction industry, but also by insurgent groups like the Taliban for improvised explosives.

It was a component in the bomb at the 1995 Oklahoma City attack.

In agriculture, ammonium nitrate fertiliser is applied in granule form and quickly dissolves under moisture, allowing nitrogen – which is key to plant growth – to be released into the soil.

Lebanese soldiers search for survivors after the massive explosion in Beirut Hassan Ammar Hassan Ammar

Lebanon’s General Security chief Abbas Ibrahim said the material at the port had been confiscated years earlier and stored in the warehouse, just minutes from Beirut’s shopping and nightlife districts.

Under normal storage conditions and without very high heat, it is difficult to ignite ammonium nitrate, Jimmie Oxley, a chemistry professor at the University of Rhode Island in the US, said. 

“If you look at the video (of the Beirut explosion), you saw the black smoke, you saw the red smoke, that was an incomplete reaction,” she said. 

“I am assuming that there was a small explosion that instigated the reaction of the ammonium nitrate - whether that small explosion was an accident or something on purpose I haven’t heard yet.”

That’s because ammonium nitrate is an oxidiser – it intensifies combustion and allows other substances to ignite more readily, but is not itself very combustible.

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For these reasons, there are generally very strict rules about where it can be stored: for example, it must be kept away from fuels and sources of heat.

In fact, many countries in the European Union require that calcium carbonate to be added to ammonium nitrate to create calcium ammonium nitrate, which is safer.

In the United States, regulations were tightened significantly after the Oklahoma City attack. 

Under the Chemical Facility Anti-Terrorism Standards, for example, facilities that store more than 2,000 pounds (900 kilograms) of ammonium nitrate are subject to inspections.

Despite its dangers, Oxley said legitimate uses of ammonium nitrate in agriculture and construction has made it indispensable.

“We wouldn’t have this modern world without explosives, and we wouldn’t feed the population we have today without ammonium nitrate fertiliser,” she said.

“We need ammonium nitrate, we just need to pay good attention to what we’re doing with it.”

Includes reporting by © – AFP 2020