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Environment

New technique recycles 100 percent of household plastic

By Ben Coxworth
December 15, 2010
New technique recycles 100 percent of household plastic
Prof. Jan Baeyens with plastic for the fluidized bed reactor (Photo: University of Warwick)
Prof. Jan Baeyens with plastic for the fluidized bed reactor (Photo: University of Warwick)
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Prof. Jan Baeyens with plastic for the fluidized bed reactor (Photo: University of Warwick)
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Prof. Jan Baeyens with plastic for the fluidized bed reactor (Photo: University of Warwick)

This Christmas, chances are you’ll save the plastic film and blister packs that your presents come encased in and send it all off for recycling. According to scientists from the University of Warwick, however, only about 12 percent of plastic sent to depots actually gets recycled. Because of problems such as glued-on paper labels, or different types of plastic being combined in one product, the rest of it goes to the landfill or is burnt as fuel. Those same scientists have now devised a system that could recycle 100 percent of household plastic.

The Warwick system is based around a unit that utilizes pyrolysis within a fluidized bed reactor. Pyrolysis is the use of heat in the absence of oxygen for the decomposition of materials, while fluidized bed reactors pass a gas or liquid through solid granular material at high velocity, causing it to behave like a liquid.

The researchers shoveled a wide variety of mixed plastics into the reactor, which were then broken down into useful elements that could be retrieved (in some cases) through distillation. Those elements included wax, which could be used a lubricant; original monomers such as styrene, that could be used to make new polystyrene; terephthalic acid, which could be repurposed in PET plastic products; methylmetacrylate, that could be used to produce acrylic sheets; and carbon, which could be used as Carbon Black in paint pigments and tires. The char left over at the end of the process could reportedly also be sold as activated carbon.

“We envisage a typical large scale plant having an average capacity of 10,000 tonnes of plastic waste per year,” said lead researcher Prof. Jan Baeyens. “In a year, tankers would take away from each plant over £5 million (US$7.7 million) worth of recycled chemicals and each plant would save £500,000 (US$777,291) 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 (US$77,729) a year, the system will be commercially very attractive and give a rapid payback on capital and running costs.”

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EnvironmentRecyclingPlastic wasteEnvironmentally-friendlyUniversity of Warwick
5 comments
Ben Coxworth
Ben Coxworth
Based out of Edmonton, Canada, Ben Coxworth has been writing for New Atlas since 2009 and is presently Managing Editor for North America. An experienced freelance writer, he previously obtained an English BA from the University of Saskatchewan, then spent over 20 years working in various markets as a television reporter, producer and news videographer. Ben is particularly interested in scientific innovation, human-powered transportation, and the marine environment.

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5 comments
Slav Ilyin
This is being done on a commercial level already.
-Actually, just started a day ago.
In this case, however, the plastic is converted into gasoline, diesel, butane, and very few other trace gases. -With a 1% non-toxic residue going to landfill. About 1 kilo of plastic (mixed) is converted to one litre of fuel.
-very exciting stuff, you\'ll should take a look! .....
plastic2oil.com -don\'t let the name fool you ;) -it is low sulphur fuel that is produced.
Facebook User
But will the EU recognise it as a recycling process, or will they deem it all to be waste products from waster products, as they did with a car tyre recycling treatment which produced heavy fuel oil, also created in England?
And, even worse, does this process deal with PVC, which the EU wants to ban altogether because incineration of it (at normal incinerator temp.) creates dioxins and furans? Will they ban yet another good idea because they did not think of it, and they cannot see how to tax it?
Wombat56
I\'m reminded of the process the Australian company Molectra uses to recycle tyres. They can selectively break the tyres back into their chemical components, depending on what\'s the most valuable on the day.
http://www.molectra.com.au/web.aspx?pageid=703
Facebook User
All the technology required to build processing plants capable of taking in unprocessed solid waste and sewage and produce separated recyclables, clean water and electricity has existed for at least 30 years. What could be separated depends on what of the non-metal waste would be saved or burned to power the plant and/or generate electricity.
The issue is putting them all together in one plant. Most of the processes are already in use, but at different places. Eddy current generators to magnetically separate shredded metals into ferrous and non-ferrous types plus sorting out non-metallics at the same time. Float and bubble tanks that can separate many types of plastics by density and how well different sizes of bubbles stick to the surfaces of small chunks.
Oil and other useful liquids could be collected from the shredders as they break up oil and other chemical containers. That raw collection could be sold to oil refineries or burned to provide power or process heating.
Paper recycling plants use \'star wheels\' to separate paper and cardboard from heavier waste, usually processing clean paper product waste from packaging.
Waste that has food waste and sewage could be pulped and strained then the strained out stuff rinsed before going through more processing.
There are ways of using waste heat from some processes to dry wet waste and as part of water purification systems.
There\'s much more already available, it just needs someone with the vision AND someone who can get people with $$$$$$$$$$ to fund the R&D. Large cities like New York, where thousands of garbage trucks each make a single one mile collection run per day, followed by a long trip to a distant landfill, could provide much of their own electricity and clean water, plus many tons of metal and other materials, if they\'d commit to fully processing all their waste.
William H Lanteigne
The economics work just fine as long as the feedstock (recycled plastic) is cheap or free, but as soon as the demand becomes significant, it will be neither free nor cheap. CWT discovered this some years ago with their Thermodynamic Depolymerization process (TDP).