Sorting machine with conveyor belt, which transports the shredded plastic waste. Credit: Fraunhofer IOSB
Recycling black plastics, such as those found in car instrument panels, used to be impossible because their absorption properties made them simply invisible to typical analysis systems. But Fraunhofer researchers have developed a new technology that can sort black plastics according to type – and at affordable prices.
Shopping at the supermarket inevitably results in a trash bin overflowing with plastic refuse. Whether it's juice, meat, fruit, or other food items, it's all packaged in plastic. The quantities are enormous – Germany alone produces roughly 5.7 million tons of it each year. Although the majority of people conscientiously put these packaging into their yellow recycling bins, only about 42 percent of the waste gets "reincarnated" as diapers, fleece pullovers, stuffed animals, and the like. The rest is sent to waste incineration plants, where it is converted into energy.
Black plastics in particular suffer this fate because it has thus far been impossible to sort them by material type. Conventional sorting systems operate specifically within the near-infrared range, which in general allows them to categorize plastics. But what works especially well for most plastics fails for black ones: the soot that gives them their dark color absorbs most of the signal, so the optical system cannot see these substances.