A matter of identity

SORTING out similar types of plastics from waste may now be possible through a system based on the different ways various plastics reflect a near-infrared light (Environmental Science and Technology, Vol 27, No 7). The different reflection patterns are then analysed by an artificial nerve-like computer programme, which is "trained to recognise" the plastic by its resin type.

Kathy Alam and her team at the Sandia National Laboratories in Albuquerque, who developed the system, claim it has been used to sort out most types of plastics with absolute accuracy.