End of life options for composite materials
The use of composite materials in manufacture of products in all sectors is growing. Inevitably the amount of waste is also growing, though in some areas advances in manufacturing are leading to leaner processes with less manufacturing waste. The “composite” nature of these materials and the predominantly cross-linked matrices used give them excellent stiffness, strength and durability. This makes them difficult to recycle, but solutions have emerged and continue to be improved for gaining value from end-of-life composite materials, contributing to a circular economy.
Check out our advice page: What can I do with my waste?
Carbon Fibre Composites
Several companies now exist to recycle carbon fibre composite waste, including ELG Carbon Fibre in UK. These use variations of a pyrolysis process which thermally decomposes the resin, leaving clean carbon fibres. Some use of chemical recycling processes is active at small scale. Applications include milled and chopped fibres, typically compounded with thermoplastics for strength and electrical conductivity. Increasing quantities are being used in mats which can be commingled with thermoplastic or pre-impregnated with resin, then pressed into parts, e.g. for automotive panels or aircraft interiors.
Glass Fibre Composites
There are several potential routes for glass reinforced polymer (GRP) waste, though recycling is more challenging, because the material value is an order of magnitude less than carbon fibre.
- Cement kiln processing: Composite waste can be co-processed with other wastes as solid recovered fuel (SRF) in cement kilns. This recovers energy from the organic part, and mineral fillers and glass become feedstock for cement clinker.
- Incineration: GRP can be sent to energy from waste (EfW) plants. Energy is recovered from the organic fraction. The incinerator bottom ash may be processed into aggregates or used in construction applications, though in some cases it is still landfilled.
- Mechanical recycling to fine filler: GRP can be ground to a fine filler, and this is done in some cases in-house with manufacturing waste. However, it is not generally economical, since the energy input is not viable to grind to a filler which replaces a low value product such as calcium carbonate.
- Mechanical recycling with fibre retention: GRP can be ground to a lesser degree, leaving bundles of fibres which have reinforcing properties. This uses less energy and provides a more valuable product than fine filler. This is done in-house to a small degree, but there is potential for higher volume applications for GRP regrind in UK, e.g. in infrastructure products with recycled mixed plastics.
Numerous research projects are seeking to gain more value from recyclate, particularly using chemical and thermal processes. For a fuller discussion, download the report Composites Recycling - where are we now, 2016
Landfill tax now stands at £94.15/tonne (2020-2021 rate), making the cost of landfill, including gate fees and transport, typically £130 to £140 per tonne. While sharp increases in landfill tax are not expected, Germany and several other European countries have already largely banned landfill. The European Commission’s Circular Economy Package seeks to increase recycling rates and reduce the amount of municipal waste that can go to landfill to 10% by 2030. It is not yet clear how this will affect industrially derived and construction waste other than packaging (75% must be recycled by 2030).
The European Waste Framework Directive (2008/98/EC) sets the basic concepts and definitions related to waste management and develops a “polluter pays” principle known as extended producer responsibility. It requires EU Member States to apply the waste management hierarchy: Prevention, Re-use, Recycling, Recovery, Disposal. Article 11.2 stipulates that "by 2020 a minimum of 70% (by weight) of non-hazardous construction and demolition waste… shall be prepared for re-use, recycled or undergo other material recovery" (including backfilling operations using waste to substitute other materials).
The End-of Life Vehicle Directive (ELV, 2000/53/EC) sets targets which currently (as of 1 January 2015) require 85% by weight of vehicles to be reused or recycled, and 95% to be reused, recycled or recovered. (‘Recovered’ here means burnt for energy recovery.) Similarly the Waste Electrical and Electronic Equipment Directive (WEEE, 2012/19/EU) sets collection, recycling and recovery targets for electrical goods.
Composites UK reports FRP Circular Economy Study 2018 and Composites Recycling - Where are we now? 2016 at End of Life and Recycling
Accelerating Wind Turbine Blade Circularity, Cefic, EuCIA, WindEurope, May 2020
Technical Sheet - End of Life Solutions, Composites UK Technical Sheet