Only approximately 12% of plastic found in household plastic and packaging is currently processed.

Now Warwick University has developed a process which could mean 100% of this type is waste can be recycled.

Municipal plastic solid waste is often too time-consuming and labour intensive to separate and clean and ends up going straight to landfill rather than being recycled.

University of Warwick engineers have invented a process that can cope with every piece of plastic waste and can even break some polymers, such as polystyrene, back down to its original monomers (styrene in the case of polysterene).

The researchers have devised a unit which uses pyrolysis (using heat in the absence of oxygen to decompose of materials) in a ‘fluidised bed’ reactor.

Tests have shown that the researchers have been able to literally shovel in to such a reactor a wide range of mixed plastics, which can then be reduced down to useful products. Many of these products can then be retrieved by simple distillation.

The products the Warwick team have been able to reclaim from the plastic mix include: wax that can be then used a lubricant; original monomers such as styrene that can be used to make new polystyrene; terephthalic acid which can be reused in PET plastic products, methylmetacrylate that can be used to make acrylic sheets, carbon which can be used as Carbon Black in paint pigments and tyres, and even the char left at the end of some of the reactions can be sold to use as activated carbon at a value of at least £400 a tonne.

This research could have a significant impact on the budgets of local authorities and produce considerable environmental benefits.

The lead researcher on the project, University of Warwick Engineering Professor Jan Baeyens, said:
“We envisage a typical large scale plant having an average capacity of 10,000 tonnes of plastic waste per year.

“In a year tankers would take away from each plant over £5 million worth of recycled chemicals and each plant would save £500,000 a year in land fill taxes alone.

“As the expected energy costs for each large plant would only be in the region of £50,000 a year the system will be commercially very attractive and give a rapid payback on capital and running costs.”

The work will be of great interest to local authorities and waste disposal companies who could use the technology to create large scale reactor units at municipal tips which would produce tanker loads of reusable material.

Alison Brown

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