Recycling: the decontamination quest

Going green is red hot, and nowhere more so than with plastics recycling.

According to a 2013 study prepared for the Canadian Plastics Industry Association, there is nearly country-wide access to recycling for the more common types of plastics packaging, with some 95 per cent of Canadians having access to recycling PET and HDPE plastic bottles, almost that many having recycling access for other bottles, and 61 per cent having access to the recycling of plastic bags and other films.

There are two types of plastics used in recycling: post-consumer and post-industrial rigid plastics, which are mainly PP, PS, and PE. Usually either purchased from manufacturers or gathered from local authority collection schemes, these materials are transported to a recycling plant, sorted according to type and color, and then, depending on the condition of the material, either dry granulated or washed and granulated to remove labelling and/or residue product. After laboratory testing, the cleaned and graded flakes and granules are stored until they’re ordered up by plastics processors — who are moving in faster than tween girls for Justin Bieber tickets.

“Plastics converters all over the world are keen to get their hands on cheaper raw materials, a requirement that can only be satisfied by resorting to secondary raw materials,” said Werner Herbold, managing director of recycling equipment maker Herbold Meckesheim GmbH. “We’re seeing particularly strong demand from countries that have not seemed very interested in recycling up until now, in particular Canada and the U.S.”

And when it comes to selling the finished product to the converters, decontamination is the whole enchilada: if the material hasn’t been decontaminated properly, you might as well use it for confetti at a wedding.

GETTING CLEAN

It’s no surprise, then, that recycling equipment makers are prioritizing the improvement of decontamination capabilities. And they’re cleaning up their acts fast.

Take PP, the strength and high melting point of which make it the most widely used plastic packaging in Canada, the U.S. and the U.K. Precisely because PP is also one of the fastest growing areas of plastics recycling, for some end uses it’s important to remove odor and traces of food contamination — which is where U.K.-based plastics design and recycling consultant Nextek Ltd. comes in. Nextek has created a two-step process to decontaminate food-grade PP for reuse back into food packaging. The initial melting phase reaches nearly 500°F to remove contaminant molecules, and then solidification under vacuum at about 280°F causes residual molecules to migrate for final removal. The finished product achieves the necessary values of food-grade content, Nextek said, and can be blended with virgin PP at rates up to 50 per cent,

PET is another commonly recycled plastic — so much so that it has the number “1” as its recycling symbol. But it can be tough to decontaminate, in part because conservation and protection techniques for beverages and food often clash with recycling exigencies. Faced with this PET recycling issue, Johnsonville, S.C.-based Wellman Plastics Recycling recently installed a pre-washing and sorting system from Amut Recycling Division. Centred around Amut’s new elliptical ballistic separator, the system separates the bottles from any and all pollutants by extracting contamination through the grates in the blades and removing it on a disposal conveyor. A de-labeller/pre-wash system then cleans the PET bottles before sending them to sorters on the plant floor.

SEPARATE WAYS

LDPE is another material gaining popularity among recyclers, and Next Generation Recyclingmaschinen GmbH (NGR) is ready with a new system designed for efficient separation of impurities from post-wash LDPE that incorporates an automatic band melt filter. “Although LDPE flakes exit the NGR washing line in good condition and at moisture levels lower than one per cent, impurities still need to be removed,” said Michael Heinzlreiter, NGR’s head of marketing. “With the automatic band melt filter system, the fineness of filtration can be tuned down to 0.275 inches. The system has a throughput capacity of 1,450 kg per hour, and screen changes can be done within 18 seconds.”

And suitable for any material in any plastic recycling facility, DLS metal detectors from S+S Separation and Sorting Technology GmbH are mounted over the conveyor system prior to the shredder, and are designed to detect magnetic and non-magnetic contaminants even if they’re embedded in the plastic product. By removing contamination prior to the process, the company said, recyclers minimize machine damage and production downtime while guaranteeing product quality.

If these technologies don’t exactly make decontamination sexy — and probably nothing can — they might get processors looking for quality regrind at least a little excited.