Rubbish collection seems complicated these days. Where I live, I use five different bins and the collections are fortnightly. Unlike many people I observe, I squash things like aluminium cans and plastic milk bottles. It seems logical and reduces the volume of rubbish stored in the house – but does doing so help collection and recycling?
• Most material recovery facilities use conveyor belts. First, magnets detect metal, but the remaining materials are processed by shape. Flat things are considered to be cardboard; 3D objects are glass (which smashes), plastic or aluminium. This metal isn’t magnetic but can be separated using electric eddy currents induced by a magnetic field. Very flat items will not make it to this sorting stage.
So flattening cans and plastic bottles can lead to them being processed as cardboard, rather than the materials they are. Sophisticated material recovery facilities use lasers, weights and buoyancy to separate materials, but these are not commonplace.
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More beneficial is to wash your items. Any smell in the bin is likely to be food remnants, not aluminium or plastic. And never put plastic bags in recycling, unless you live in one of the few areas that can deal with them.
Marty Middlebrook, Planet Ark Environmental Foundation, Sydney, Australia
• In the 1970s, I worked in a large hospital. In order to reduce the space that waste took up, the management bought a compactor to reduce it to bales. But the idea was short-lived because the first collection was declined. The refuse firm also had compactors. Already-compacted waste gave its compactors indigestion.
Roger Miles, St Albans, Hertfordshire, UK
• Most collection vehicles compress the rubbish as they go along.
Alastair Mouat, By email, no address supplied
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