BIOCHEMICAL AND ENVIRONMENTAL ENGINEERING GROUP: recycling difficult materials

Our patented technique for recycling high-performance consumer packaging has found commercial success, and we are now looking for new collaborations to apply it to other waste materials, such as car tyres and oils

The challengeSome materials are very difficult to recycle, with obvious implications for the environment and future generations. We have been looking in particular at how to recover chemicals from high-performance packaging (used for products such as toothpaste tubes and pet food pouches). We have now found that the same technology can be adapted to recover reusable chemicals from waste tyres, engine lubricants, plant oils and some types of plastics.

The usefulness of high-performance packaging materials is not in question. Plastic-aluminium laminate packaging has benefits to both consumer and producer: they are cheap to make, lighter and greener to transport, convenient to use and allow long shelf life of the contained product. However, until recently they have not been recyclable.

Our work in tackling thisOur research between 1999 and 2002 supported by EPSRC funding established a way to recycle useful chemicals from high-performance packaging. The technique stems from a chance observation made by a friend who accidentally microwaved his bacon roll for too long, reducing it to a lump of char. This phenomenon triggered us to investigate microwave heating (more accurately termed micro-wave induced pyrolysis) as a way to recycle chemicals from laminate packaging.

Material challenge: plastic-aluminium laminate packaging is green in many ways, but has been hard to recycle. Our technology extracts from it clean aluminium, as well as oils and gases.

Methodology We found that by applying microwaves to shredded pieces of the packaging immersed in a bed of carbon particles, we could recover clean aluminium as well as hydrocarbon oils and gases, all of which have significant commercial value. Not only is the packaging saved from landfill but reclaiming the aluminium this way has a carbon footprint only 34% of that of producing new aluminium from bauxite.

To commercialise the technique we created the award-winning University spin-out company Enval Limited. At first we built a pilot-scale test unit and then the first commercial-scale plant which started operation in 2013.

Potential applications 1. Recycling old car tyres

We have also demonstrated the use of microwave-induced pyrolysis for the ‘productive’ destruction of old car tyres. Car tyres are not readily recycled or reused; many end up littering the environment. Microwave pyrolysis of tyres yields copious amounts of oils and hydrocarbon gases, steel wire (from the bracing bands) and carbon black. One proposal is to develop a mobile trailer unit which could be taken to where the waste tyres are located and conduct the processing and collection of reclaimed products in situ.

2. Recycling waste oils In addition we have found that waste oils can be processed by this

technology to produce fuels for petrol or diesel engines. The waste oils we have studied include waste car engine oil, natural plant-derived oils as well as waste polyethylene plastic.

We are now looking to collaborate with anyone interested in applying our microwave technology to the recycling of the types of hydrocarbon-containing products described above.

Our techniques and skillsl Microwave-induced pyrolysis, including reactor designl Assessment of hydrocarbon converting processes

What is new about our work? We believe that we are at the forefront of developing waste-treatment solutions using microwave-induced pyrolysis.

Current industrial partnershipsHigh-performance packaging: own company Enval.Car tyres and oil recycling: none.

Professor Howard Chase, University of Cambridge, Department of Chemical Engineering and Biotechnology, Pembroke Street, Cambridge, CB2 3RA Tel: 0044 1223 334781 Email: hac1000@cam.ac.uk Web: http://www.ceb.cam.ac.uk/directory/howard-chase

The team

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Clean and pure: the recovered aluminium is free of impurities and ready for re-use.

Recycling in action: Enval’s industrial unit near Huntingdon is the first commercial-scale plant to recycle flexible laminate packaging. Unlike incineration, pyrolysis takes place without combustion so no greenhouse gases or toxic emissions are produced.