IR spectroscopy sorts waste for further recycling

NOVEMBER 5, 2009--In Norway, most waste sorting takes place in the home, but several European countries have chosen other solutions. In Germany, packaging waste ranging from wrapping paper to cardboard boxes and no-refund bottles is sorted at approximately 200 sorting centers. The sorting plants are financed by producers of the packaging in accordance with the cost of recycling their products.

The solution developed by SINTEF is based on infrared spectroscopy, using ordinary halogen lamps as the light source. In the selected range of infrared wavelengths, objects have different reflection properties than for ordinary visible light. This is advantageous because the computer can distinguish between plastic-coated cardboard, ordinary cardboard, and different kinds of plastics by small variations in the color of the reflected infrared light.

The automated sorting machines have been so successful that Ferd (the owner of Elopak, which initiated the development) established its own company -- TiTech Visionsort (formerly Titech Autosort) -- that is now producing the units in larger numbers. Systems have been developed that can sort any combination of common domestic plastic waste and beverage cartons. The largest machines can currently handle ten tons of waste per hour on a conveyor belt that is 2.8 m wide, with a speed of 2.5 m/s. When sorting bottles, the selected plastic fraction is 97% pure and 95% of the desired packaging type is picked up from the conveyor. More than 800 sorting units have been delivered to recycling facilities in Europe, Japan, Korea, Australia, and the United States.

For more information, go to www.sintef.no.

--Posted by Conard Holton, Vision Systems Design, www.vision-systems.com