An Insight into Asbestos by Dr Tim Johnson

In ancient times there was a belief in the existence of the salamander, a legendary creature based to some extent on the lizard of the same name, that lived in fires. There were also accounts of objects being made from ‘salamander fur’ that could be cleaned in a fire without being damaged. To me, that sounds like an animal so useful that, had it existed, it would have been hunted to extinction long before now, so who knows, perhaps it did exist after all! Even at the time many hearers of these fantastical tales were sceptical, but it is possible there is some truth behind these myths, although clearly not about the heat resistance of certain lizards. This is because it now seems highly plausible, with the benefit of hindsight, that the sheets of un-burnable cloth that so amazed onlookers were in fact made from mineral fibres of the asbestos family.

These stories illustrate just how long mankind has been using asbestos for its attractive mix of physical properties and widespread availability. Indeed there are reports of asbestos fibres being used to strengthen earthenware cooking pots in Finland dating back 4,500 years. Its use expanded greatly during the industrial revolution, leading to the start of commercial mining in the UK in the late 19th century. Asbestos-based materials continued to be widely used in a dizzying variety of applications until the mid-1980s, until many countries started to place heavy restrictions or outright bans on brown and blue asbestos. The use of white asbestos was later banned in the UK in 1999 and many other industrialised nations have similar measures in place. Of course, these restrictions have come in as a direct result of the increasing awareness of the very serious and well-known dangers to human health that can result from exposure to asbestos fibres. What is less widely appreciated is that the damage caused to the lungs and the subsequent illnesses that follow are a result of the sharp needle-like form of the mineral fibres, rather than because of the chemical composition of the mineral itself, which is relatively unremarkable and entirely benign.

Current regulations in England and Wales classify any waste material containing more than 0.1% asbestos as ‘hazardous waste’. The waste has to be removed under strictly controlled conditions, placed in special plastic bags and sent to carefully designed and managed landfill sites for safe disposal/storage. However, this is becoming increasingly costly, especially when legacy responsibilities costs of the landfill are included, and although production and import of asbestos-based products ceased many years ago in the UK, a large amount remains in place and disposing of these materials safely is now becoming a major issue as the affected buildings need to be replaced or refurbished.

The list of products that have contained asbestos over the decades is enormous. Some look truly bizarre with the benefit of hindsight, such as filters for cigarettes or gas masks. However, most applications are in the construction industry, such as lagging for pipes, dry wall linings, ceiling panels, floor tiles, cement-based products for roofing etc. and also in brake disks, heating elements and other domestic equipment. Given this historical background, it does not take long to realise that one of the problems with asbestos-containing waste is that it is almost always mixed up with a number of other materials. For example, electrical cables were often lagged with asbestos blanket for added fire resistance, with the result that the waste generated by the replacement of these cables is a mixture of copper (a valuable metal), a plastic or rubber insulating sheath (which can give rise to hazardous organic compounds if burnt) and asbestos (which is fire resistant and hazardous).

Here at Tetronics, we have noticed a clear increase in enquiries about the treatment of asbestos-containing wastes, both in the UK and abroad. Motives behind this trend include not only the cost-effective disposal of a hazardous waste but also a desire to find an economic method to recover valuable metals from the mixed wastes and in some cases as a result of increased corporate social responsibility. From all these viewpoints, the ability to completely destroy the hazard, rather than to merely store the problem for future generations to deal with, is a powerful incentive to consider alternatives to the current status-quo.

Tetronics has practical experience of the successful treatment of asbestos using its plasma arc technology stretching back many years. Plasma is a very ‘omnivorous’ technology and will ‘eat’ most things, so treating a waste containing a mixture of materials is familiar territory, and the high temperatures ensure the complete destruction of the deadly needles by converting them to an inert material suitable for use as a construction aggregate. The well-proven ability of plasma to recover valuable metals from other hazardous wastes adds another level of resource recovery and lends even greater economic and environmental weight in favour of the use of DC plasma arc technology for the treatment of this difficult waste.

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