Organics Waste Recycling

Removing Contaminants From Compost

When it comes to organics waste recycling, having the right technology in the right places can help boost profitability for commercial composters by enabling production of better-quality compost. Komptech Americas has developed proven organics waste processing technologies that help you efficiently remove contaminants like plastics and glass and improve the quality of your compost products.


Quality compost is a high-demand product that is widely used as fertilizer and soil amendment for residential, commercial and agricultural applications. Compost that is made from recycled food waste has a high potential for contaminants like plastic and glass, which can ruin the quality and ultimately the value of the finished compost. Contaminants that make it into finished compost generally are too small of a particle size to be able to be removed. Therefore, the first, and most important step in organics decontamination is education on the front end of the recycling process.

Despite the tremendous efforts of municipalities and waste processors around the country to provide public guidance on proper recycling techniques for food waste, it still only takes one bag of plastic or glass garbage mixed in with compostables to jeopardize an entire batch of compost. It is critical that a concerted effort be given to succinctly educate populations in both urban and rural communities on proper separation of compostable items BEFORE they enter the general waste stream. Through education we can improve the purity of organics to be recycled, create better quality compost and divert more methane-producing organic materials from landfills.


Sorters at the front end of organics processing lines are there to manually remove large contaminants like glass bottles, shoes, lawn tools and more. Grinding directly onto the sort line belt can quickly overburden sorters with material depths that are unmanageable. By screening materials before they hit the sorting line, fines can be removed and larger contaminants can be distributed more evenly onto the belt for easier identification and more efficient sorting and picking.

A trommel screen like the Komptech Nemus 2700 is perfect for pre-screening organics waste. The horizontal drum allows materials to ride on the screen surface as it moves it from one end of the drum to the other, removing fines through the screen holes and keeping glass contaminants intact without breaking. By pre-screening prior to sorting, processers save money on wear and fuel costs on their grinders by eliminating further processing of fines and increase efficiency and effectiveness of their manual sort lines.


One of the biggest problems with compost contaminants is size. Many commercial compost processors grind their incoming food waste with high-speed grinders. While these high-speed machines may increase throughput, they also subsequently grind down plastics and other contaminants to less than 1/2-inch and end up contaminating the finished compost product. By keeping particle sizes large, contaminants remain easier to sort, separate and remove down the processing line.

A low-speed shredder, like the Komptech Crambo, is built for organics waste processing. The Crambo, with its counter-rotating shredding drums and aggressive teeth, shreds to a coarse-cut, producing material that maintains porosity and airflow. More importantly, the low-speed shredder minimizes fines, keeping the size of plastics and other contaminants large enough for easy mechanical separation and removal.

Crambo dual-shaft shredder processing green waste


If plastics and other contaminants do end up making it into the windrow pile, they can still be removed if the particles remain large in size. Once those contaminant pieces become smaller than 1/2-inch, they are nearly impossible to remove from finished compost. It is important during the windrow turning process that the contaminants in the windrow do not get further reduced in size by the turning equipment. This is easily solved by using a windrow turner with a drum engineered to turn the compost effectively without reducing contaminant size, vs. high-speed drums that utilize knives that chop up material and further reduce contaminants.

One of the key differentiating features of the Komptech Topturn X Series compost windrow turner is its drum engineering. Komptech turners feature large diameter turning drums engineered to create the optimum tall, peaked windrow shape while enabling complete mixing of the row from outside to in. This moves the hot, wet compost from the middle of the windrow to the outside, and the dry materials from the outside to the middle, without reducing the size of contaminants. Using the chimney effect, air (O2) is drawn in from the base and heat (CO2) is released from the top.


Following the windrow composting process, it is critical to remove the remaining contaminants from the overs fractions. This prevents reintroduction of contaminated overs back into the composting process. If plastics and other contaminants make it into the fines fractions, they will end up in the finished compost product. This “Screen With Windsifting” process can be completed easily with either a star screen or a trommel screen followed by a windsifter separation machine.

The Komptech Hurrikan S is a mobile, high-throughput windsifter that efficiently removes light plastics, film and foils from screened overflow particles using a patented “pressure-suction“ process that enables an effective separation and removal of light fractions from screened compost in two steps. First, material is separated by a targeted air knife. Then, lightweight material is drawn out by a powerful suction blower, adjustable to separate material by variation of blower speed, blower distance and vent flaps. The material then goes over a head-pulley magnet which removes metal contaminants followed by a stone trap which removes rolling fractions such as rocks and other round contaminants.


Compost industry expert Todd Dunderdale, CCP™ recently presented an in-depth overview on the importance of contaminant removal from organics waste in commercial composting. Please complete the form below and view the complete video presentation.