Paris (AFP)

Presented as the origin of the devastating explosions in Beirut, ammonium nitrate is mainly used as a "nitrogenous" fertilizer for agricultural use, but can also enter into the composition of certain explosives for civilian use.

- Uses

Ammonium nitrate "is mainly used as a nitrogen fertilizer for leafy legume crops", indicates the Chemical Society of France.

This type of fertilizer, which comes in the form of white granules, is used all over the world for better yields and is considered indispensable by many farmers.

Thus, in Gironde, Benoît Labouille cultivates on 200 hectares of corn, rapeseed and vegetables partly in conventional, partly in organic: it indicates Wednesday to AFP to use each year "a little more than 10 tons" of ammonitrate , a fertilizer composed of ammonium nitrate, "on almost all conventional crops".

This nitrogen fertilizer formula is "very useful", he says, because "directly assimilable by the plant" which needs nitrogen to develop and thus benefits from a "small boost". "It's super important," he sums up. He specifies storing this fertilizer "in clean, dry sheds" and away.

Lebanon is known to be a large consumer of fertilizers: with 330 kg per hectare, the country uses twice as much as the world average, noted in February the United Nations Food and Agriculture Organization (FAO ).

Ammonium nitrate is also used in the manufacture of explosives. "Mixed with TNT (trinitrotoluene) or pentrite, it is used in construction, mines and quarries", specifies the Chemical Society of France.

Other minor uses exist for this chemical body, as a propellant in the aerospace industry for its oxidizing properties. Dissolved in water, it causes an endothermic reaction used for cooling bags. In beekeeping, the white smoke that a small amount of nitrate produces when burning can anesthetize bees in order to be able to move a hive.

- Manufacturing, price and storage

Ammonium nitrate (NH4NO3) is the result of the reaction between ammonia and nitric acid.

Russia is by far the leading producer country, with nearly 10 million tonnes in 2017, or 45% of world production, according to the FAO.

Mainly used in agriculture, it is subject to price seasonality: the average price per tonne was 214 euros at the end of 2018 / beginning of 2019, according to the European Commission.

The compound, like its derivatives, are subject to strict rules: it is necessary "to isolate the storage of fertilizers from products incompatible with ammonium nitrate, especially in the event of fire", specifies a technical sheet from the Ministry of Agriculture, which cites in particular flammable liquids, pressurized liquefied gases or corrosive liquids.

He points out that one of the main dangers associated with fertilizers containing ammonium nitrate is "the detonation of high dosage ammonitrates", ie those containing more than 28% nitrogen. He adds that "this danger is generally considered unlikely for products conforming to the standard and stored under normal conditions".

For the Norwegian mineral fertilizer manufacturer Yara, "in general, ammonium nitrate-based fertilizers are safe if they are handled according to European regulations and those of the sector," he told AFP, specifying that it respects for its part "strictly security standards, which also apply to service providers".

- Main risks and consequences

"Insensitive to impact and friction, ammonium nitrate is a + poor + explosive unless it is mixed with fuels such as hydrocarbons, or if it is melted and confined during, for example, a violent fire" , indicates the Chemical Society of France.

"The detonation wave of ammonium nitrate causes very significant destruction. It is wreaking havoc, its accidentology is well known. The explosion in Beirut is one of the strongest explosions of chemicals in history," said AFP Daniel Vanschendel, explosives expert.

"Explosions are typically detonations that cause enormous damage due to the supersonic shock wave, which is clearly visible on videos" from Beirut, comments Andrea Sella, chemist at London University UCL, quoted by the Science Media Center.

According to him, this is a "catastrophic regulatory loophole, because the rules on the storage of ammonium nitrate are very clear."

In view of "the first white fumes, followed by an explosion which released a large red and brown cloud, then a white cloud in the shape of a + mushroom +, this indicates that the gases emitted are vapors of white ammonium nitrate , toxic nitrous oxide and water ", adds Stewart Walker, professor at the Australian University of Flinders.

mlb-myl-kd-eco-burs / pn / pcm

© 2020 AFP