The separation and extraction of metals has assumed an importance that could scarcely have been foreseen even a few years ago. Partly this is a consequence of EU regulations – the End-of-Life Vehicles and Waste Electrical and Electronic Equipment Directives have both put a premium on metal recovery and reuse – but also, and perhaps more compellingly, there is money to be made, particularly for non-ferrous material.

According to the BMRA (British Metal Recycling Association), a tonne of ferrous scrap might net you £200 in today’s market conditions, but a tonne of copper can fetch £3,000 and a tonne of nickel anything up to £9,000. For the silver and gold that can be found in the printed circuit boards of motor vehicles, that figure rises even higher.

One consequence of this is that metal separation technology has been rapidly evolving. “The metals recycling industry has already made large strides in advancing separation techniques in recent years,” says Howard Bluck, Head of Environment at the BMRA. “Companies continue to invest millions of pounds annually in improving the efficiency and recovery rates.”

The most common method of metal extraction in the UK is still the shredder, which uses rotating magnetic drums to extract iron and steel from a mixture of metals and other waste materials. However, to extract the valuable non-ferrous materials, metal waste usually has to go through a further separation process. There are a number of ways this can be achieved.

Eddy current separators work by inducing an electromagnetic force into non-ferrous material, so the magnetic fields of the various metals repel each other, thus separating. Elsewhere, air classification uses cyclone technology to achieve the same effect, whirring non-ferrous material up so that particles of different weights eventually fall and separate from each other. Liquid systems, on the other hand, use a slurry of water of a specific gravity in which some low density metals (say aluminium) will float and high density ones like zinc or copper sink.

Of the three techniques, the most reliable and cost-effective is widely thought to be the eddy current separator. “They are the great mainstay of metal separation,” say Brian Gist, Sales Engineer at TiTech, a supplier of recycling and sorting technology. “They are reasonably economic to buy and very economic to run.” Air separation and liquid systems are generally more expensive and only economical when used on bulk quantities. Many of the media plants that process and separate this material are now being built without air classification because of the cost involved and the fact the systems often need a lot of maintenance.

There are, however, further methods. One of the systems TiTech has developed is the optical sorting machine Combisense. “It uses a high-definition colour camera,” explains Gist. “We physically look at the material and either separate via very fine colour differences in material and/or the shape of the material. Typically, it’s usually used to differentiate between brass and copper material.” The company has also introduced a sensor-based system called the TiTech Finder that uses infrared technology to detect different polymer types and types of non-ferrous metal.

Of course, there are plenty of small firms using cheaper, albeit low-tech, options. Cooler Recycling Solutions run an operation whereby metal is separated and sorted manually. “We have trained operatives to recognise different types and segregate them,” explains Quality Manager Roger Milton. “Then we use grinders and shears to separate and compact into bales.
“People are absolutely amazed when they come round to see our operation because it runs so smoothly. Last year we achieved our target of only three per cent landfill and we have set ourselves a target of only one per cent landfill this year.” It’s comforting to know that for all the high-tech wizardry at work in this sector, there is still room for the human touch.