Making high-quality compost is a challenge for the plant, because the organic waste it receives contains high amounts of contaminants. In among the apples, potatoes and oranges are plastic bags and even the occasional can or glass jar.
“We spend a lot of money each year sorting out the contraries,” says Heinisch. The USUM team manually removes larger items upfront. The subsequent careful prepping with the Crambo and extensive rotting processes ensure that foreign objects aren’t reduced to small pieces. This permits screening with a 20 mm screen cut.
Heinisch: “Screening gives us about 60 volume percent fines and 40 volume percent overs, the latter heavily contaminated with plastic, metal and stones. Our leased Komptech Hurrikan S wind sifter removes about 95 percent of the contraries from that fraction, or about 30 percent of the total.” Currently USUM has to dispose of the screen overflow as well as the contaminants. However, the fees for the screen overflow, which makes up about two thirds of what remains, are now much lower. For Komptech Sales Engineer Karsten Runge, the positive balance is clear: “The costs USUM saves for disposal are estimated to cover all costs for fine compost processing, including contraries removal.”