Lately the increasing amount of contraries in compost has been endangering the high quality of the soils made with it, and the acceptance built up over so many years of hard work. The contraries come from people throwing the wrong things in the organic bin, and most of these are plastic. With experience and passion for composting, Komptech are working with other technology companies on machines and process solutions to make a usable compost product out of contamined biowaste.
A lot of the contraries in biowaste can be removed during processing, as long as they aren’t shredded too small. Excessive shredding of plastic materials is best avoided by using low speed shredders. Komptech offers single-shaft Terminator and double-shaft Crambo shredders for the purpose. Both can be configured for selective shredding by means of settings and equipment options for the shredding unit.
Screening before composting is becoming more important. For example, pre-composting screening at 80 mm and removing or sorting the overs is an option for heavily contamined feedstocks. For this purpose coarse screening drum and star screens can be used, and in some cases disc or spiral shaft separators. These technologies are available from Komptech in a wide range of capabilities, in most cases with versions for both stationary and mobile use.
It is evident that screening machines will need to handle smaller grain sizes in future. Screening technologies combining vigorous material movement (star screens, flip-flow screens) and screen meshes of eight mm and lower are in development. Currently, automatic sorting machines that use near infrared or colour and image recognition to separate contraries from biogenic waste are not in general use. But an increasing number of plants are deploying this kind of technology for compost, compost overs or the shredded feedstock.