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Thermal Technologies – overcoming the variability of waste by Dr Tim Johnson

28th February 2012 in What’s been happening

One of the most difficult aspects of waste treatment is that ‘waste’ is
a highly variable thing.  By its very nature, waste comes from an almost
unlimited number of sources and in a huge range of compositions and
forms.  Unfortunately, this inherent variability makes it harder to
select the right waste treatment process for each pile of waste.
Thankfully, many wastes can be kept separate as they are being produced
and this makes finding the right treatment option much easier.  For
example, catalytic converters, old tyres and used engine oil all come
from cars that end up in scrap yards, but they are pretty easy to keep
separate from each other during the dismantling process.  This general
principle of keeping wastes separate, or ‘segregation’ as it is known in
technical-speak, can be seen spreading to most areas of waste
management, as anyone will testify who (like me) has the weekly
excitement of feeding multiple green bins, brown bins, black boxes and
blue sacks with the correct parts of their household waste.  Not
bothering to segregate your waste certainly makes throwing things away
much easier, but since all the goods we use are produced in separate
industrial processes it is not very surprising that recycling those
things at the end of their useful lives works best when the waste is
also separated into piles of similar objects.

In several of my previous blogs I have explained how Tetronics’ plasma
technology can be used to treat specific waste streams and often to
extract valuable materials or energy from them, so that ‘disposal of
waste’ becomes ‘recovery from waste’.  Naturally, each of these
processes depends on someone making sure those waste streams are kept
nicely segregated from other things.  The good news is that the list of
wastes suitable for a ‘recovery’ process is growing all the time, as
Tetronics and other waste treatment innovators roll out new
technologies.  However, it is clear that eventually, after all materials
suitable for recycling and recovery have been picked out, there will
still be a motley collection of unwanted wastes with no elegant and
economic treatment solution.  For these wastes a more generic treatment
solution is required, one that can accept everything from liquids to
solids, flammable or non-flammable, hazardous or benign.

There are very few such treatment processes available and historically
the choices have tended to be restricted to landfilling and
high-temperature incineration, both of which have their drawbacks.  In
the case of landfilling of generalised hazardous and industrial wastes
this was often preceded by mixing various different types of waste
together in an attempt to create a mixture that was less hazardous than
the sum of its starting materials.  For some years now regulators have
frowned on such practices because in many cases the ‘treatment’ amounted
to little more than dilution of hazardous materials rather than
rendering the waste non-hazardous in any true sense of the word.  Even
when materials are encased in concrete (a process known as
‘cementation’) the hazardous aspects of the material often still remain
for future generations, it is just that the materials are contained more
effectively in the short term.

Happily, Tetronics plasma technology offers the sort of generic waste
treatment solution that many local authorities, waste operators and
communities are looking for.  Plasma furnaces are very ‘omnivorous’
animals and will eat more or less anything, since using plasma to heat
waste up to 1600°C results in almost everything melting or being
vaporised.  Plasma’s combination of high temperatures and high
ultra-violent light leads to efficient destruction of organic pollutants
and the capturing of heavy metals in a glassy non-leaching material
suitable for inert disposal or reuse as aggregate.  The fact is, all
materials look fairly similar at plasma furnace temperatures, which
means that although treating a mixed bag of very different wastes in a
single process will never be easy, the enormous versatility and
effectiveness of Tetronics’ plasma technology looks certain to make it
an increasingly obvious choice for the treatment of hazardous and
industrial wastes around the World.

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