As we stand in our living rooms looking at the mountain of Christmas packaging around us, it’s good to hear about a new technique claimed to allow 100 percent of plastics to be recycled.
Currently, many people go to a lot of trouble separating out plastic waste – but few realise that typically only 12 percent of ‘Municipal Plastic Solid Waste’ is actually recycled, with the rest ending up as landfill or being burnt.
It’s often simply too time consuming to separate out the different plastics or remove labels, and in any case objects are often made of more than one plastic that would require different treatments.
However University of Warwick engineers say they have come up with a simple process that can cope with every piece of plastic waste and can even break some polymers, such as polystyrene, back down to their original monomers.
The Warwick researchers have built a unit which uses heat in the absence of oxygen to decompose materials – known as pyrolysis – in a ‘fluidised bed’ reactor.
Tests completed this week have shown that it’s possible to literally shovel in a wide range of mixed plastics and reduce them down to useful products. Many can then be retrieved by simple distillation.
The products the Warwick team has been able to reclaim include wax that can be used as 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 and carbon which can be used as Carbon Black in paint pigments and tyres.
Even the char left at the end of some of the reactions can be sold for use as activated carbon at around $600 a tonne.
The team is now working to commercialise the process.
“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,” says engineering professor Jan Baeyens.
“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.”