Waves of technology

Features - Plastics Update

Recyclers handling mixed plastics can choose from several methods that harness light waves to automate the sorting process.

January 8, 2015

Manufacturers of everything from packaging to consumer electronics to automotive components choose plastic as the optimal material for their applications.

But as both product designers and recyclers know, saying they use “plastic” is a gross oversimplification when referring to the seemingly infinite varieties of resins and compounds that are used in the manufacturing process.

Engineers use specific polymers for their inherent qualities, whether rigidity or flexibility; resistance to heat or cold; or porosity or non-permeability. Then, product designers may choose any of hundreds of colours to make the item attractive.

The end result of these decisions makes the task of recyclers difficult, as they are ultimately asked to take centrally collected, commingled plastics and turn them into sorted, usable fractions of the same polymer and colour.

Market and regulatory forces, however, seem to be pointing toward a need for the speedy adoption of effective automated plastic scrap sorting of this material in places like Europe and North America in particular.

Eyes for detail

At recycling plants around the world, workers at sorting stations dismantle all manner of postconsumer electronics and identify materials by resin and colour for further processing.

Although performing this same task with postconsumer bottles is now a rarity in the developed world, there are still places where the hand-sorting of plastic bottles continues.

In these applications and others, however, large-scale processors have for decades been working with technology providers to automate the identification and sorting of such plastics.

The use of optics — sensors that emit light waves to identify colours and chemistries — has been a foremost option explored by technology providers and adopted by recyclers.

Postconsumer plastic beverage bottle sorting was the focus of much of the early experimenting with optical sorters, but technology providers and recyclers of mixed, shredded plastics (derived from electronic scrap and even automobiles) have increasingly worked together to bolster the presence of automation in those sectors.

At a presentation at the 2014 Electronics Recycling Asia event, held in Singapore in November, Patrick Lindweiler of Cologne, Germany-based Steinert offered an overview of his company’s product line for the sorting of shredded WEEE (waste electrical and electronic equipment) materials.

Rinse and repeat

Markus Zimmerman of Germany-based equipment and technology provider Herbold Meckesheim provided delegates to the 2014 Electronics Recycling Asia event, held in Singapore in November, with an overview of how density separation using water can be deployed to separate the various plastic fractions of the WEEE (waste electrical and electronic equipment) stream.

The company’s washing plants are used in a variety of applications, with WEEE plastics separation being one of the latest sectors for a company that was founded in 1884.

In a plastics processing system described by Zimmerman, water is introduced at the shredding and granulating stages, with a follow-up friction washer being used to further remove contaminants such as paper fibres, sand, dirt and any other fines.

Using flotation to identify materials by their inherent densities can then be accomplished with a series of separation tanks. Zimmerman said PS (polystyrene), PP (polypropylene) and ABS (acrylonitrile butadiene styrene) can all be separated from metals this way. As well, PVC (polyvinyl chloride) and plastics containing BFRs (brominated flame retardants) also can be removed.

Steinert has long produced magnetic devices that help differentiate ferrous from nonferrous scrap and different types of nonferrous scrap from each other. In recent decades, the company also has turned its attention to the design of near-infrared (NIR) optical devices to help automatically identify and sort plastic resins common in the post-shredded WEEE stream, including ABS and polystyrenes.

Lindweiler said NIR technology is particularly useful in sorting mixed black plastics, as some other types of optical technology are not effective with black materials.

Steinert’s UniSort models use what it calls hyper-spectral imaging (HSI) to perform some identification tasks. HSI sensors can view objects using a wide range of the electromagnetic spectrum. When the sensors are asked to identify certain objects based on their electromagnetic “fingerprints,” these objects—after being scanned and identified—can be diverted as a positive or a negative sort.

For recycled plastic consumers who wish to keep out plastic scrap that has been treated with brominated flame retardants (BFRs), X-ray transmission technology can identify these pieces, said Lindweiler.

In the field

Felix Hottenstein of MSS Inc., a subsidiary of the United States-based CP Group, also provided Electronics Recycling Asia delegates with a plastics sorting technology overview and how such equipment is deployed in the field.

Hottenstein said NIR technology plays a key role in several units made by MSS, including its Cirrus models marketed to WEEE processors.

The NIR technology used in Cirrus machines has been designed to offer a high level of pixel resolution, said Hottenstein. It can be programmed to identify and sort a wide variety of resins commonly found in shredded WEEE scrap, including ABS (acrylonitrile butadiene styrene), HIPS (high-impact polystyrene), PC (polycarbonate) and PC-ABS. As well, said Hottenstein, the device can be programmed to remove unwanted non-plastic contaminants.

Users of such automated equipment can “decide where the value is and set up their sensors accordingly,” said Hottenstein, to “extract the valuable fractions from the mixed material.”

In typical WEEE NIR sorting applications, NIR sorters are deployed “after magnets and eddy currents and then induction sorters” remove all marketable metals.

Thus, in the ideal setup both clean, marketable metals fractions and then clean marketable plastics fractions are produced with minimal hand sorting.

Hottenstein said optical units have been designed to be incorporated into existing systems, and that MSS has worked on numerous retrofit projects where optical sorting has been added downstream.

Shifting people’s perceptions of affordability also has helped increase the spread of optical sorting. Hottenstein said sensor units are designed to last at least 10 years, so thus the return on investment can be spread out if necessary. In his experience, Hottenstein said the conveyors running beneath sorting units are likely to be replaced before the sorters, and that when recyclers replace their optical sorters it’s because they are seeking new technology rather than because of any malfunction with their original unit.

Prompts for automation

For recyclers to invest in automation they need to be convinced of both a reasonable return on investment (ROI) and the likelihood of a long-term market for their products.

A number of presenters at the RePlas (Autumn) 2014 event, which took place in November in Shezhen, China, referred to regulatory measures and market forces that are prompting recyclers to process plastic scrap closer to its point of generation rather than shipping it unsorted several thousand miles to its ultimate point of consumption.

Zhou Yachun of the Department of Customs Control and Inspection of China’s General Administration of Customs (GAC) told delegates to RePlas that “after Green Fence [we] constructed a long-term mechanism” and that GAC has maintained “certain measures and policies.”

Green Fence involved “very forceful measures,” said Zhou. “We kept those effective measures and regulations and adjusted some measures that were too strict.”

Another speaker, this one from GAC’s Bureau of Anti-Smuggling, warned or reminded the assembled recyclers that as of Sept. 10, 2014, certain Customs violations are “not just a legal problem but a crime. I have to warn all the leaders of the companies that you have to pay attention to this.”

The Bureau of Anti-Smuggling speaker referred to GAC Article 152, which now identifies “solid waste smuggling” as a severe crime that could mean “prison for up to five years” for those responsible, or more than five years for quantities of more than 20 metric tons of material.

According to the www.npc.gov.cn website, the paragraph added to Article 152 reads:

“Whoever, evading Customs supervision and control, transports solid waste, liquid waste or gaseous waste from outside China into the territory of China, if the circumstances are serious, shall be sentenced to fixed-term imprisonment of not more than five years and shall in addition, or shall only, be fined; if the circumstances are especially serious, he shall be sentenced to fixed-term imprisonment of not less than five years and shall in addition be fined.”

Zhou of GAC said plastics recyclers remain in the spotlight, in part because of media reports in China that single out mixed plastic shipments as “foreign garbage.” He also said, “There are too many [plastic scrap] nonconforming shipments, and that’s the issue the media cares about the most.”

Regarding mixed plastic scrap imports, Zhou said, “The appearance can be really bad, so journalists like to write stories about plastic scrap.”

Despite the scrutiny plastic scrap receives in China, the world’s growing middle class and its finite natural resources portend well for the recycling industry’s future.

Ma Hongchang, a Beijing-based consultant on Chinese affairs for the Brussels-based Bureau of International Recycling (BIR), told RePlas delegates that recycling is being driven both by resource scarcity and governmental mandates. The European Union (EU) has set a goal of recycling 60% of its municipal solid waste by 2030, noted Ma, while its current rate may be as low as 25%.

The private sector has likewise made commitments to recycling, with Ma mentioning the goal of United States-based retailer Wal-Mart to incorporate some 1.4 million tons of plastic scrap in the making of its packaging materials by the year 2020.

The United States-based American Chemistry Council (ACC) is recognising plastics recyclers such as QRS Recycling, based in St. Louis in the U.S.

QRS was honored in late 2014 with one of the ACC’s 2014 Innovation in Plastics Recycling Awards. The company has established plastics container recovery facilities (PRFs) to sort plastics for which local material recovery facilities (MRFs) cannot typically find destinatioins. Many of them are domestic markets.

The processes being developed by QRS and its vendors is likely to be sought out throughout North America, Europe and other parts of the world as the drive to automatically capture more plastic scrap continues.


The author is the editor of Recycling Today Global Edition and can be contacted at btaylor@gie.net.