After gracing us with several eco-oriented features in recent months, including last week's survey on business and climate change, The Economist decided to take on recycling in the current issue's Technology Quarterly section. After first unequivocally stating that, yes, recycling is "worth the effort," citing its benefits in conserving natural resources, reducing the amount of burnt and buried waste and in saving energy, the magazine focuses on the advances made by several cities and firms in dealing with the growing amounts of municipal waste.
It notes that while recycling facilities continue to employ people, investments in the area have shifted away from more traditional sifting technologies that rely on individuals sorting the materials to more advanced optical sorting technologies that can separate different types of plastic and paper automatically. One company that has benefited from this move to modernize recycling systems is TiTech, which developed the world’s first NIR (Near InfraRed) sensor for waste sorting applications after being founded in 1993. It now has over 1,000 of its systems installed in over 16 countries worldwide.
The company's systems use spectroscopy to identify and sort different materials. Paper and plastic items that are spread out on a conveyor belt in a single layer are illuminated by a halogen lamp, which, because of the unique combination of wavelengths in the infra-red spectrum reflected by each, allows the materials to be identified individually. A computer analyzing the sensor's data is thus able to determine the type, shape, color and position of each item.
A defined sorting fraction is then blown onto a second transport system by air jets while the residual fraction is brought to a third conveyor belt for further disposal and sorting. The company claims that the materials are sorted with up to 98% accuracy and that the capacity of each system ranges from 1 to 10 tons per hour. In addition, sorting criteria can rapidly be adjusted with a single click and software upgrades can easily be downloaded via a modem.
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