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News

Plastic film recycling - end of the road for landfill and incineration?

Institution Of Chemical Engineers (IChemE) : 16 March, 2014  (Special Report)
The large-scale incineration or dumping of plastic films in landfills could soon be a thing of the past as new technologies seek to convert plastics into fuels and other useful products. However, Axion Consulting – a UK-based waste processing consultancy specialising in plastics recycling – believe it is now technically feasible and economically viable to begin the large scale collection of low grade plastic films for conversion into fuels and other recycled products.
Plastic film recycling - end of the road for landfill and incineration?
Economic factors and fundamental difficulties with handling and sorting at recycling facilities have resulted in plastic film recycling still being in the early stages of development, especially in comparison to recycling processes for dense rigid plastics such as Polyethylene Terephthalate (PET) used widely in the drinks industry.
 
As a result, policy around the world has looked at alternative solutions to reduce the impact of plastic films, especially plastic bags, on the environment. Controversial policies have included the banning of single-use plastic bags and imposing charges on consumers.
 
Speaking at the 12th European Gasification Conference – organised by the Institution of Chemical Engineers (IChemE) in Rotterdam, The Netherlands, 10–13 March 2014 – Sam Haig, IChemE member and senior engineer at Axion Consulting, said: “Plastic films are lightweight and 2D in shape and can easily get mixed into other recycling streams, such as paper, causing contamination. They also have a tendency to get trapped in recycling machinery requiring regular maintenance. As a result, plastic films have been excluded from most public household waste collection schemes around the world."
 
“However, a new generation of machinery uses a flow of air to help detect and remove around 95% of films from co-mingled kerbside waste collections. The process is likely to be more economical and efficient than current machine-based and hand-picking operations. Importantly, the recycled films can be used for products including refuse sacks and signage for retailers.”
 
Haig continued: “Our analysis also suggests that it is now economically viable to convert low grade plastics into fuel. We studied five chemical engineering processes and concluded that three: fast pyrolysis; depolymerisation; and gasification with biological treatment provided significant financial returns over a ten year period.
 
“The more efficient sorting of films at recycling facilities and the conversion to fuels are clearly better solutions than disposal in landfills or by incineration. However, avoiding irresponsible disposal in the first place and increasing our efforts to re-use plastic films and bags should be the priority for everyone.”
 
Plastics and recycling
  • Most consumer products made from films have short lives and include plastic shopping bags and wrapping for food such as bread, fruit and vegetables. Generally, these are made of Low Density Polyethylene (LDPE) or High Density Polyethylene (HDPE).
  • Consumer products made from rigid plastics can be categorised into short-life and long-life.
  • The most common short-life applications are in product packaging and include bottles used for soft drinks – Polyethylene Terephthalate (PET); milk – HDPE; cleaning products – Polypropylene (PP) and HDPE; food trays – PP; and pots – PP.
  • Long-life plastic items are generally parts of products in and of themselves: TVs, fridges, car parts, etc.
  • There is a huge range of different types of plastic used in order to cater for particular niche requirements, but the main ones are PP and Polystyrene (PS).
  • Some plastics are governed by legislation dictating recycling targets e.g. End-of-Life Vehicle Directive, and Waste Electrical and Electronic Equipment Regulations). Plastic packaging is not subject to this type of legislation.
Why some plastics are currently not recycled
  • Rigid plastics are much denser and more rigid than films. They are much easier to transport and handle in recycling facilities.
  • Plastic films have a tendency to pick up and retain moisture and contamination much more than rigid plastics. This also makes them more difficult to identify during sorting.
  • Many plastic films are constructed as multi-layer sheets of several different types of plastic, which means they are not as easy to re-extrude to a suitable product.
  • Commercial and public relations (PR) factors also influence recycling. Drinks manufacturers have rolled out PR initiatives to enable ‘closed loop’ recycling of their own bottles.
  • The commercial values of recycled ‘clear’ PET and ‘natural’ HDPE streams are much higher than PP, PS and PVC (or coloured PET/HDPE).
The challenges when recycling plastics
  • All plastics have to be sorted to keep levels of contamination low.
  • The challenge lies in separating the different plastic types and the end markets for the recycled products.
  • Clear PET bottles are used almost exclusively for drinks, as are natural HDPE bottles. This means it is possible to sort on both polymer type and colour to produce a food grade plastic that can be re-manufactured into a bottle.
  • PP, which along with LDPE, HDPE and PET make up the vast majority of consumer plastic packaging, is not as easily sorted. In the UK, many authorities do not collect them as part of their kerbside collections.
  • Material Recovery Facilities (MRFs) are not typically set-up to produce a purified PP stream.
  • In addition, PP is used for fatty foods and cosmetics requiring the packaging to be thoroughly washed before it can be re-extruded.
  • Recycled PP cannot be reused in food-grade packaging applications as non-food-grade PP makes up a large proportion of the PP waste and cannot yet be effectively sorted from food-grade PP. The recycled plastic can only be used as non-food-grade polymer attracting a lower value than food-grade. The economics of recycling PP are not as favourable as PET and HDPE.
Recycled plastics and fuel
  • Depending on the technology used, low grade waste plastics can be converted into diesel or gasoline-like products, or into Synthesis Gas (Syngas). The product can undergo further processing into a variety of products including ethanol.
  • Syngas can be used in an on-site Combined Heat and Power (CHP) engine, or the diesel, gasoline and ethanol products can be blended with road fuels to power vehicles.
  • Current technologies advertise a conversion ratio of 1000kg waste plastic = 1000 litres fuel oil; a syngas to ethanol plant could theoretically have a conversion ratio of 1000kg waste plastic = 750 litres ethanol.
Plastics and landfill
  • In the UK, current data suggests 1.7m metric tonnes of consumer plastic packaging – 1.1m rigid, 0.6m film – were consumed last year. Only 440k metric tonnes was collected for recycling.
  • It is estimated that over 1.2m metric tonnes of plastic, used in consumer packaging alone, is not being recycled.
  • Should plastics which are difficult to recycle be phased out?
  • Plastics are part of our everyday lives and each type has been developed specifically for its unique properties. It would be challenging to phase out these difficult to recycle plastics.
  • The solution is to provide the right infrastructure for collection, sorting and recycling.
Future household recycling
  • There is a lot of discussion about the ‘best’ way to collect and recycle all household materials, including plastics.
  • There are also questions about which plastics we should be using.
  • However, the major change to recycling in the future needs to be a drive towards the next generation of technologies which will allow the recycling and re-use of more of our materials, including plastic films.
  • Consumers also have a responsibility re-use and dispose of plastics responsibly.
  • Axion Consulting is a division of Axion Recycling Limited. The company was formed to develop and operate innovative processing solutions to recover value from waste resources. Axion Recycling was formed by directors Keith Freegard and Roger Morton in 2002 to find innovative ways of recovering resources from waste. Further details: http://www.axionconsulting.co.uk 
References
 
 
 
 
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