Tackling Complex Plastic Recycling Challenges

Recycling and sorting processes may have been playing catch up with plastics production and uses but modern technologies are now allowing operators to achieve sorting purity levels of 99.9%...

Plastics production may have increased exponentially with demand, but most of this material has ended up in landfill. Recycling technology has been playing catch up but now it’s possible to achieve sorting purity levels of 99.9% from fractions as small as 1mm. This article looks at progress in recycling plastics that have previously been difficult to treat, such as black trays and from WEEE.

Globally, plastics production has continued to rise for more than 50 years, reaching 233.75 million tonnes in 2013. Growth in end-use industries such as packaging, building and construction and automotive is expected to continue to rise, with predictions suggesting plastics production will increase to 334.83 million tonnes by 2020*.

Currently, PE accounts for the largest market volume globally, with PET expected to be the fastest growing product segment for plastics between now and 2020. The three largest producers of plastics by region are China (24.8%), followed by Europe (20%) and NAFTA - United States, Canada and Mexico (19.4%).**

Despite more countries gradually putting in place measures and legislation to recover and recycle plastics, landfilling remains the first option for millions of tonnes of plastics globally. However, an increasing number of countries are starting to recognise that waste plastic should instead be regarded as a valuable resource that should ideally be recycled or, where that’s not an option, used to fuel waste to energy facilities.

The continued growth in demand for plastics coupled with growing pressure to find alternatives to landfill has, understandably, focused attention on the role that recycled plastics can play in the manufacture of new plastics products. Conventional plastics recycling methods have been unable to meet the stringent quality levels required by plastics manufacturers for inclusion in the manufacture of new products but, over the past ten years, automated sorting technology has completely revolutionised plastics recycling.  

Advances in automated sorting technology are enabling exceptionally high purity results in plastics recycling – from coloured and clear types of plastic such as PET and HDPE, to other polymers including polypropylene, polystyrene and PVC. As long as the right legislation, infrastructure and, in particular, sorting technology is in place, it is possible to achieve previously unfeasible purity levels of over 99.9%. Recovered end fractions can be used to produce recycled products such as fibre for the textile industry or to make new sheets or new PET bottles, demonstrating that a closed-loop approach for plastics is entirely feasible. 

From food grade rPET and plastic films, to opaque PET and WEEE, sensor-based sorting technology is helping recycling companies globally achieve ground-breaking recovery and purity results in some of the most complex and challenging plastics recycling applications.

Food grade rPET   

PET bottle recycling is the most widely established plastics recycling application globally, but when it comes to meeting the high purity and quality levels demanded by customers for food grade recycled PET (rPET) flakes, many recycling companies have struggled.

In light of this challenge, TOMRA Sorting Recycling has developed the AUTOSORT flake sorter that combines a visible range spectrometer camera (RGBVIS) to detect colour and non-transparent contaminants, a near infrared (NIR) spectrometer to detect different polymer types such as PET, HDPE, PP, PVC, PA, PS, PLA, etc and also a metal sensor to detect ferrous and non-ferrous particles. The AUTOSORT flake sorter is capable of identifying and sorting flakes as small as 2mm.

TOMRA is currently involved in a project for French company Regene Atlantique – part of the SUEZ Group. Regene Atlantique operates a PET recycling plant in Bayonne in south west of France where four AUTOSORT units and the new AUTOSORT flake sorter are installed. Using this bespoke combination of technology, Regene Atlantique can achieve the quality levels required by some of the biggest soft drinks companies in the world. Contamination levels are set by these customers of below 10ppm (parts per million) on PVC, below 3ppm on metallic (ferrous and non-ferrous particles) and less than 200ppm on other unwanted material such as other colours or polymers.

Separating food and non-food PE

Sensor-based technology is also capable of detecting different types of PE and one application where this capability is being exploited is the separation of food and non-food packaging. Most non-food PE is coloured (shampoo bottles and detergents, for example), but in some countries natural or clear PE is now being used for non-food packaging. It is virtually impossible for the human eye to distinguish between the food and non-food PE but sensor-based sorting makes this distinction possible.

Another unit has been developed by TOMRA that uses an extended wavelength scanner to detect the difference between and separate the homo (food) and co-polymer (non-food) material. It is effectively separating two polymers within one polymer group. Purity rates on both end fractions of close to 100% are achievable.

This process is already in place at Australian packaging and resource recovery company, Visy Industries Australia Pty. The company has installed a bottle-to-bottle recycling facility in New South Wales, Australia, for the food-grade production of PET and HDPE regranulate. The plant is the first of its kind in Australia and produces 2,500 – 2,900kg of recycled food-grade PET pellets and up to 1,500kg recycled food-grade HDPE pellets per hour. The recycled PET pellets are used by Visy in its own preform production, while the food grade rHDPE pellets from milk bottles are sold to customers worldwide.

Although demand for food-grade recycled HDPE is high, it is extremely difficult to produce and Visy is currently one of only a small number of HDPE food-grade recyclers in the world. Separate collection streams – e.g. for HDPE milk bottles – are an important prerequisite but only exist in a few countries such as the UK and Australia. Currently there is no legislation that requires plastic manufacturers to include recycled content in new products, but a number of large companies and even industries – the UK’s dairy industry for example – have committed to their own targets for the inclusion of recycled content.

Opaque PET

With global demand for PET bottles continuing to rise rapidly, one challenge that plastics recyclers face is how to recover white opaque PET bottles, which are widely used for dairy products such as milk and drinking yoghurts. Opaque is used in PET bottles to protect the contents from light and oxygen, however this can cause problems with recycling. The opaque bottles affect the end product because most NIR sensors are not able to detect and separate them out. However, using sensor-based sorting technology, it is possible to detect and recover all types of opaque PET bottles. The AUTOSORT unit is capable of recognising the different colours and the different NIR fingerprint of opaque PET bottles, enabling this increasingly popular plastic material to be recovered and recycled for the first time. This process is proving very popular with all of TOMRA’s PET recycling customers globally.

PET trays

In recent years, the packaging industry has significantly increased its use of PET trays. Currently, multilayer PET trays, normally used for meat products, are separated from PET bottles during the recycling process to increase the value of the PET bottles. Left in, the multi-layer trays would contaminate the PET bottles so it makes sense to recover them separately. 

The sorting technology used in TOMRA’s AUTOSORT is capable of detecting this kind of multi-layered PET product and, over the past two to three years, a number of customers have been able to separate the PET trays, maximising the value of their PET bottles and maintaining very high end quality levels.

With the use of PET trays in packaging likely to increase, organisations such as Plastics Recyclers Europe are providing recycling guidelines for PET trays and encouraging separate sorting streams to enable PET tray recycling and develop markets for this packaging product.  

Black plastics

Another application where sensor-based sorting technology is breaking new ground is black plastics. Rigid black plastic packaging is commonly used for pots, tubs and trays. The infrared cameras found in NIR sorting systems can’t detect the carbon in black plastics because it reflects almost no light in the visible part of the spectrum and also strongly absorbs in the ultraviolet (UV) and infrared (IR) spectral range. Consequently, this material hasn’t been recyclable. Now though, studies are underway by WRAP (Waste & Resources Action Programme) and UK-based plastics design and recycling consultants Nextek Ltd, to look at whether adding a pigment or marking to the bottles or trays would make the material detectable and recoverable using AUTOSORT.

PE foils

The past two to three years have seen a rise in the recovery and recycling of PE foils – or films – used in packaging. Using the latest automated technology, it is now possible to achieve 100% recycled content clear foils. To achieve this, a two-stage process using the AUTOSORT firstly separates out the target material (in this case PE foils) from the other in-feed material and a second stage targets the contamination to remove all fines and improve the purity of the end fraction.

The end fraction of PE foils is then suitable for extrusion and use in new product manufacturing, completely closing the loop on plastic films. The market for this relatively recent plastics recycling application is already strong in France, Germany and Spain where a number of waste companies have introduced this process with great results.

Recovery of valuable plastics from WEEE

The recovery of plastics from WEEE is perhaps one of the most challenging plastics recycling applications. Historically, the EU has driven developments in this field by introducing regulations that govern the treatment of this complex waste stream and demand that disused electrical equipment must be separated and recovered or recycled. Since the initial introduction of the EU legislation in 2002, more and more countries have followed suit, introducing regulations that aim to ensure the safe recovery and recycling of WEEE.

WEEE has a complex composition and encompasses items from computers, office electronic equipment and gadgets, to mobile phones, television sets and refrigerators. WEEE includes used electronics which are destined for reuse, resale, salvage, recycling, or disposal. Typically WEEE contains ferrous metals (40%), non-ferrous metals including PCBs (25%), plastics (30%), glass, wood and other materials (10%).***

The range of plastics within the infeed material will vary at every WEEE recycling facility, but with mixed plastics accounting for approximately a third of WEEE, operators are recognising that WEEE contains some rare, high value polymers that can be recovered for reuse. As an example, the plastic used in car windscreens to prevent glass shattering has a current market value of around €800 per kilo.

Traditional sorting methods simply can’t deliver the detailed sorting required. You can’t, for example, hand pick the metal elements off a plastic backed circuit board and a human being can’t tell whether a piece of plastic contains flame-retardant and could therefore contaminate an entire batch. Sensor-based sorting, on the other hand, is capable of identifying and separating different types of plastics which can then be transformed into reusable granules.

Following initial separation and removal of metals, the residual fraction consists of almost metal-free plastics. This material then goes onto an AUTOSORT unit, where the material can be further sorted by any colour and any polymer required. For plastic recovery, the focus is on the main polymers ABS, ABS-PC, PS, PE, PP and PC.

Whereas conventional treatment can’t recover these resources, modern systems are able to identify and separate each individual polymer. Using conventional treatment, the optimum particle size to detect and sort is between 8 to 80mm, whereas the bandwidth of specialist sorting solutions such as TOMRA’s spans from 1 to 150mm.

The recovery of plastics from WEEE is a small but developing market, with particular growth in Asia.  Customers worldwide are recycling certain plastics to a 99% purity level and consequently selling recovered material at a much higher market value. One such customer is Korean-based MERC (Metropolitan Electronics Recycling Center), which is run by the Korea Electronics Recycling Cooperative, Korea’s WEEE association.

MERC’s 21,000 tonnes per annum recycling plant processes refrigerator shredder scrap. In January 2015, the plant’s existing mechanical treatment equipment was replaced with a new sensor based sorting system from TOMRA. This unit separates plastics by polymer type and a COMBISENSE unit upgrades the quality of recovered copper and aluminium. MERC’s sorted ABS (98.3% purity) and PP (93.2% purity) fractions are now achieving five times the value of mixed plastics, there is minimal loss of valuable metals and the upgraded copper (99.2% purity) and aluminium (97.8%) is achieving a higher market value than previously.

With continued growth in global demand for plastics predicted, TOMRA will continue to invest in research and development and work closely with plastics manufacturers and recycling companies worldwide to identify new plastics recycling opportunities.

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Dr Ralph Uepping is technical director of recycling and Frédéric Durand is plastics segment champion from TOMRA Sorting Recycling.

*Source: Gread View Research Marketing and Consulting: Plastics Market Analysis By Product (PE, PP, PVC, PET, Polystyrene, Engineering Thermoplastics), By Application (Film & Sheet, Injection Molding, Textiles, Packaging, Transportation, Construction) aAnd Segment Forecasts To 2020

**Source: PlasticsEurope (PEMRG/Consultic)

*** Source: KERP Kompetenzzentrum Elektronik & Umwelt, 2009