Texas fertiliser plant explosion – experts respond

An explosion at a fertiliser plant in the US is reported to have injured more than 100 people and killed an unknown number killed in the town of West in Texas.

Our colleagues at the AusSMC collected the following expert commentary. Feel free to use these quotes in your reporting. If you would like to contact a New Zealand expert, please contact the SMC (04 499 5476; smc@sciencemediacentre.co.nz).

Dr John Price, Principal at Integrity Partners. Dr Price was formerly a Professor in the Mechanical Engineering Department at Monash University, comments:

Footage of the explosion taken from a car which appears to be about 1 km away from the plant shows a large fire which is then followed by a major explosion.  The occupants of the car are strongly affected by the shock wave from the explosion.

“It is the nature of Ammonium Nitrate fertilisers and explosives, that they can resist large fires for about half an hour, but can then detonate.  This would appear to be the situation here. The occupants of the car have been attracted to look at the fire, not realising that in Ammonium Nitrate explosions that a fire is a possible precursor to a major explosion.

“A similar large fire, followed by explosion has a been a feature of many fertiliser explosions.

“The people in the video clip are lucky to have survived, since it appears major damage occurred further away than they would have been parked.  They have survived because they are near the ground, and the undulations in the ground and where the explosion occurred have protected them from the full shock wave.

“We hear a child complaining about loss of hearing in the video.  The loss of hearing may be temporary or it may more permanent since the shock wave is associated with a pressure pulse which can affect ears.  The windows of the car appear to be fractured when the shock wave hits.”

Associate Professor David Cliff is Operations Manager at the Minerals Industry Safety and Health Centre at the University of Queensland. He has particular expertise in emergency preparedness, gas analysis, spontaneous combustion, fires and explosions. He comments:

“In reviewing some of the news stories there are a few key facts.  There are many unknowns.

“There was a major existing fire – presumably, although not definitely, the fertilizer was burning.  This fire could have heated up the pressurised containers of liquid ammonia (also called anhydrous ammonia) (to keep it liquid it has to be under pressure).  Once the pressure rating was exceeded the tanks could have spontaneously ruptured and disintegrated – so it may not have been a chemical explosion but rather an instantaneous rupturing of pressure vessels containing the anhydrous ammonia.  These explosions could have then spread the fire.

“There are other possibilities depending on the chemical processes used at the site.  It may be that the ammonia was produced on site.  The ammonia is formed by chemical reaction needing hydrogen gas and nitrogen.  The hydrogen is highly explosive.  Some processes use methane to generate the hydrogen – this is also explosive.  It the fertiliser produced comes into contact with organic materials it can form explosives – such as are commonly used in mining – ANFO is ammonium nitrate (fertilizer) and fuel oil mix.

“The sudden release of large clouds of ammonia is very dangerous – it is extremely corrosive and toxic.  There are other dangerous chemicals present such as concentrated nitric acid, that could also pose a major problem.

“It is difficult to be more definitive without knowledge of the actual plant and processes.”

Professor Clive Williams, Visiting Professor, Australian Centre for Military and Security Law, and Visiting Fellow, Strategic & Defence Studies Centre, at the Australian National University, comments:

“It is 20 years since the Waco siege come 19 April, but the greater likelihood is that this was not a deliberate act but an accidental explosion involving ammonium nitrate (AN). AN is often used in making home-made explosives and for blasting purposes when mixed with diesel fuel (known as ANFO). Accidental explosions have occurred in the past at AN manufacturing plants. Heating of AN or any ignition source may cause violent combustion or an explosion. AN reacts with combustible and reducing materials as it is a strong oxidant. Pretty much anything with “ate” in the title can be used for explosives.”

Dr David Caldicott,an emergency doctor based at Calvary Health Care in Canberra, comments:

“Anhydrous ammonia is used in the manufacture of ammonium nitrate, an extensively used agricultural fertilizer globally, and when mixed with diesel or fuel oil, produces ANFO, one of the world’s most readily available explosives.

“The live feed from West, Tx, suggests that there has been a massive explosion, several orders of magnitude greater than that of the recent Boston explosions. That will change the nature of the injuries suffered by patients, the number of patients involved and the nature of the disaster scene.

“Depending on the number of people in the vicinity of the explosion epicenter, medical professionals would be more likely to encounter victims of ‘blast type’ injury, including punctured lungs, bowel, and eardrums. Further out, shrapnel injuries would begin to predominate. Structural damage to buildings will also cause injuries and continue to pose problems to both patients entrapped and those responding to assist them.

“Significant numbers of patients are likely to have suffered injuries, and it would be extraordinary if there were no fatalities, particularly as the explosion seems to have been preceded by a fire at the plant, to which first responders would have attended.

“This represents a ‘compound disaster’ situation, in which the effects of the initial event exacerbate the overall effect. The blast has affected West’s electricity supply, which has required rapid intervention, as the evacuation has been ongoing overnight. The rural nature of the location prolongs access times and causes extended delays with ingress and egress of emergency vehicles.

“By any standards, this is a nightmare scenario for local first responders and treating doctors, many of whom would presumably be unfamiliar with injuries more often seen in a military environment. It is a major industrial disaster for the USA but at this stage there is no indication this explosion is the result of anything other than a terrible accident.”

Professor Priyan Mendis is Professor and Discipline Leader of Civil Engineering at the University of Melbourne and author of ‘Blast : why explosive devices kill people and destroy buildings‘. He comments:

“Casualties and damage to buildings etc from this event are much higher than normally anticipated from a normal explosion. But even the experts may not have been able to predict the extent of damage reported up to now in this blast . There are reports about 60-70 killed and 10-15 buildings completely demolished. It looks like this blast is from anhydrous (dry) ammonia.

“The exact cause is still not known. But these combustible materials dispersed in air when triggered can cause massive pressures in confined areas causing large explosions. As we know Ammonium Nitrate fertilizer was used in Oklahoma bombing in 1995, which was the most destructive act of terrorism in America  until the September 2011 World Trade Centre attack. A damaging fire ball is also generated in these explosions. Usually a thorough analysis is conducted to analyse the structures around these plants for possible explosions, and extra protection is provided. It looks like that has not been done here. In Australia, we are getting a bit complacent. We have many vulnerable critical infrastructures which need protection.

“My group (Advanced Protective Technology of Engineering Structures Group, APTES at University of Melbourne)  uses sophisticated computer programs to model these types of events, so we have methods to analyse possible explosions and we have tested many typical structures for large blasts, in Woomera. Just after the Bali bomb, there was some interest in protecting buildings, infrastructure etc in Australia, but now asset owners rarely pay attention to these type of events.”

Dr. Rajat Ganguly, Senior Lecturer within the School of Management and Governance at  Murdoch University, comments:

“Given the timing of this explosion, it is understandable that people’s minds would immediately drift to the possibility of a terrorist attack. While it is too early to be sure, the timing of the fertiliser plant explosion indicates that this is most likely a terrible accident. It took place in the evening, when fewer people are likely to be working at the plant, reducing the potential impact of the explosion. Also, the media would have been better prepared to react had the event happened in the daytime, increasing the amount of coverage and contributing to feelings of panic among members of the public – a useful, but sinister tool for a terrorist.

“Given the size of the explosion, I would expect the number of fatalities to be in the dozens, perhaps even hundreds. Of particular concern are toxic gases, which may have been released into the atmosphere and surrounding area. The footage is incredible, and it is clear that there is a lot of panic and uncertainty about the explosion at the moment. Thankfully, it appears there are highly trained emergency services personnel at the scene to assist and get to the bottom of this as soon as possible.”

Professor Stephen Lincoln, Professor of Chemistry in the School of Chemistry and Physics at the University of Adelaide, comments:

“The most common cause of explosions at nitrogen fertilizer plants is ammonium nitrate which is a high explosive. However, under normal agricultural usage conditions it is quite stable. To cause it to explode a military style detonator, on something similar is usually required.

“Alternatively, high temperature can cause it to explode – and as there was apparently a fire prior to the explosion this may have generated sufficiently high temperatures to cause such an explosion.  The immediate products of the explosion are gaseous oxides of nitrogen and, in the presence of atmospheric moisture, nitric acid. These are very probably the noxious gases referred to in the reports of the explosion.”