Composites: Tough materials to recycle

Written by: Stella Job | Published:

Composites, which combine two or more components to make a material that is light, strong and durable, are environmentally excellent in use but a challenge to recycle. Stella Job, supply chain and environment manager at trade association Composites UK, examines how this problem is currently being overcome in the UK

The use of fibre-reinforced polymer (FRP) composites is growing, and the global market for composite products is expected to reach $95bn globally by 2020, up 40% from 2014. Inevitably this results in more waste from manufacturing, and an increasing challenge to develop economically sustainable recycling routes for end of life. This is particularly important in automotive and construction, where regulations limit landfill. Often thermoset resins (which don’t melt) are used because of their excellent properties.

So composites have environmental benefits while they are in use, but are inherently difficult to recycle. However, following research and development, several ways to recycle composites do now exist, though they are still developing and scaling up commercially.

Carbon-fibre-reinforced polymer (CFRP) waste is now commercially recycled using a pyrolysis process by ELG Carbon Fibre in the UK. The resin is burnt off in limited oxygen, leaving clean carbon fibres. These are then either sold as milled or chopped fibres, or made into intermediate products such as non-woven mats, moulding compounds or pellets for injection moulding. Much work is going on to develop markets for these products, for example in automotive parts, and over the past few years the amount of CFRP being recycled in the UK has grown to about 1,000t/yr.

Glass-reinforced plastics (GRP) are more challenging economically, and the most promising end-of-life route is to co-process with other waste-derived fuels in cement kilns where the glass fibre and any mineral fillers are recycled into the cement while the polymer provides energy. GRP regrind from manufacturing waste can also be recycled as a reinforcing filler. Some companies do this in-house, though fine grinding is not commercially viable because of the very low cost of virgin fillers.

Dry fibre waste adds up to around 15,000t/yr in the UK, from the manufacture of raw fibres, process waste in textile production and offcuts in ply cutting.

Some textile products from dry carbon fibre waste are commercially available, and large amounts of glass fibre waste could soon be used in thermoplastic infrastructure and timber replacement products. RWW

For more information, see Composites Recycling: Where are we now? at
https://compositesuk.co.uk/industry-support/enviro...

Fact file: Composite waste

  • About 15-20kt of GRP process waste, plus possibly 50kt of GRP end-of-life waste, is produced each year.
  • A further approximate 15kt of glass and carbon fibre process waste (not bound in a matrix)
  • Around 3kt of CFRP process waste/year, but still very little end-of-life waste
  • The End of Life Vehicle Directive (ELV) requires 85% of cars to be reused/recycled
  • Waste Framework Directive requires re-use/recycle/recover 70% construction waste by 2020
  • UK composite product market could grow from its current £2.3bn to £12bn by 2030


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