Ammonium nitrate faces unwelcome spotlight - again

The past couple of months have seen a renewed spotlight turned upon ammonium nitrate, after it has been found to have been used in a number of terrorist attacks around the world. The Mumbai bombings of 13th July and Anders Breivik’s attack on central Oslo on July 22nd have both been found to have used ammonium nitrate fertilizer as their base. On a visit to Islamabad in August, US Senator Robert Casey told Pakistani officials that the CIA estimates that 80% of all improvised explosive devices (IEDs) used in Afghanistan to kill and injure US and allied troops (there have been record numbers of IEDs this year, killing or injuring 368 US soldiers so far) are based on calcium ammonium nitrate fertilizer produced in Pakistan and smuggled across the border into Afghanistan. And now suspicion has also fallen upon ammonium nitrate in the car bombing of the UN compound in Abuja, Nigeria on August 26th.

The succession of incidents has led to intense discussion in governments across the globe, and the use of ammonium nitrate as a fertilizer has come under scrutiny of a sort it has not seen since the mid-1990s, in the wake of the 1993 World Trade Center and 1995 Oklahoma City bombings in the US, and the IRA’s 1993 Bishopsgate bombing and 1996 Docklands bombing in London. The reaction this time has been swift. Even in just the first few weeks following the new set of incidents the US Department of Homeland Security has finally issued its notice of proposed rulemaking on AN – something that was mandated by Congress in 2007 but left on the back burner. India likewise has dusted off its own plans for reclassifying AN with a high nitrogen content as an explosive, and there are also reviews under way in Europe, Norway, and other Scandinavian countries. It seems a fairly safe bet that there are likely to be further moves to regulate AN around the world. Already straight ammonium nitrate is banned as a fertilizer in China, Colombia, Afghanistan, Ireland, Germany and the Philippines. Might more countries follow suit? Could this be the end of AN as a fertilizer?

Outright bans are fairly unlikely, and there are still powerful arguments for continuing the use of AN, which has definite agronomic benefits in some climates, and which is widely and safely used as a fertilizer across Europe and the CIS – but the major threat that the compound faces arguably comes not from an outright ban, which has by and large so far only happened in countries where usage was already fairly low, but rather a gradual accumulation of regulations on storage, handling, transport and security which make it too expensive or impractical or even simply too much of a hassle to use, compared to urea or various NPKs. Many dealers in the US have already stopped handling AN fertilizer because of steadily growing restrictions, and those in Europe could begin to follow suit if the regulatory burden became too onerous.

To head this off, various methods have been proposed on the production side to try and reduce the risk posed by AN. The question of ‘tagging’ ammonium nitrate to determine its origin – something that was initially proposed in the 1990s – has been raised again, as has colouring it so that it can be immediately spotted by customs officials. There have also been the usual calls to blend AN with other substances to make it less explosive, although it remains is arguable to what extent this is truly possible and still have a usable fertilizer. Honeywell sells a mixture of AN with ammonium sulphate which it claims meets Department of Homeland Security guidelines, and during the 1995-6 lawsuit against ICI Explosives that followed the Oklahoma City bombing there was also mention of a patent filed by a Samuel Porter in the US which mixed AN with ammonium phosphates to reduce its explosive characteristics. However, calcium ammonium nitrate is arguably already an attempt at such a formulation, and yet has been successfully used as an explosive by the IRA and the Taliban, as the compound can be dissolved and the AN can be recrystallised from solution.

What will happen as a result of the current focus on AN is still very uncertain, but what is not in doubt is that manufacturers and users of AN face their greatest challenge in more than a decade.