Recycling glass fibre reinforced composites – history
and progress (Part 1)
The difficulty of recycling GRP,
such as these waste trims, is a stumbling block in industries where the
pressure to recycle is high. (Picture © Filon Products.)
Under floor vent from Hambleside Danelaw.
Typically made from PP, but this one is 100% recycled with glass fibres from
ground GRP recyclate and in-house PP waste, resulting in a stiffer, stronger
product with no increase in cost. (Picture © Stella Job.)
Under floor vent from Hambleside Danelaw.
Typically made from PP, but this one is 100% recycled with glass fibres from
ground GRP recyclate and in-house PP waste, resulting in a stiffer, stronger
product with no increase in cost. (Picture © Stella Job.)
The world is going through a low carbon
revolution and the potential for composites to reduce greenhouse gas emissions
is clear. But the difficulty of recycling glass fibre reinforced plastic (GRP)
is a stumbling block particularly in construction and automotive where the
pressure to recycle is high.
The European Composites Industry
Association (EuCIA) states that GRP is
“recyclable and compliant with EU legislation,” and it is (see EuCIA issues
position paper on recycling of glass reinforced thermoset composites).
But at present facilities exist only in Germany to recycle, which for companies
in UK, for example, is prohibitively expensive and not environmentally friendly
due to the effect of transport, leaving the option only to landfill.
To what extent is GRP economically recyclable, and therefore
actually being recycled? How much would it affect markets for GRP if there were
fully functioning, economically sustainable, geographically widespread
recycling supply chains?
Several articles in Reinforced Plastics have advised us
of the development of pyrolysis based carbon fibre recycling processes and
these are now commercially available in several places since the launch of
Milled Carbon (now ELG Carbon Fibre) in the
West Midlands, UK. But the value of carbon fibre is around ten times that of
glass, so while commercialising these processes has not been easy, it has been
'easier' than finding recycling routes for GRP, despite the much smaller
volumes (76,000 tonnes carbon fibre reinforced plastic compared to about 1
million tonnes GRP parts produced in Europe in 2012, according to AVK's 2012 market report).
|
Cement
kiln route – how does it work
|
|
Incineration of GRP is not
practical since about 50-70% of the material is mineral and would be left as
ash, which still needs to be landfilled. For co-processing in cement kilns,
composite parts are size-reduced and mixed with other waste to feed into the
kilns.
GRP typically contains E-glass,
which is usually alumino-borosilicate, along with an organic resin and often
calcium carbonate filler. When fed into a cement kiln the organic resin burns
providing energy (about 12 MJ/kg of waste) and the mineral constituents
provide feedstock for the cement clinker.
The clinker is ground to form
cement. Any calcium carbonate calcines (releasing carbon dioxide) to calcium
oxide, the primary component of Portland cement. Alumina and silica also have
cementitious properties in an alkaline environment and are typically present
in Portland cement at about 25%, and in much higher proportions in cement
alternatives from fly-ash and slag. Boron, which is found in most E-glass,
can cause a reduction in early strength during the setting of cement, but as
long as proportions are kept low it is not considered a problem (ref: Pickering, Benson, Recovery of material
and energy from thermosetting plastics, Proceedings, ECCM6 – Recycling
concepts and procedures, 1993.
|
The recycling process supported by
EuCIA, and available in Germany, involves the addition of GRP waste to cement
kilns. This gains value from all parts of the composite and is commercially
active in Germany through the route known as Compocycle, operated by Zajons and feeding
Holcim’s cement kilns. However there is still a significant gate fee for the
process. In Germany regulations leave no option to landfill so the volumes of
GRP waste are sufficient to justify such a process. Composite manufacturers
such as Fiberline in Denmark have
supported that process, being close enough to take advantage of it. But this
route reduces the value of the material to that of calcium carbonate and at
present is not economic compared to landfill where landfill is an option.
Mechanical
grinding
Recycling of GRP by mechanical
grinding has been happening for several decades. Back in the 1970s the late
Wolfgang Unger was developing his proprietary Seawolf technology in Florida,
US, to grind fibreglass scrap and use it for replacing rotten boat transoms or
incorporate it using spray-up equipment for making bathtubs and other products.
Unger’s company is now called Eco-Wolf and is managed by his daughter
SabineCorinna Unger. Eco-Wolf has recently (2011) partnered with Global Fiberglass Solutions
which is seeking to build and manage facilities to collect and recycle
fibreglass across the US, having developed applications such as railroad ties
(railway sleepers).
ERCOM Composite Recycling GmbH was
established in Germany in 1990 to recycle automotive production and post-use
waste by shredding and grinding graded parts into powder, to be used in new
sheet moulding compound (SMC) in proportions up to 20% (ref: George Marsh,
Facing up to the recycling challenge, Reinforced Plastics, Volume 45, Issue 6, June 2001,
pages 22-26). ERCOM terminated in 2004. This approach of grinding
GRP to fine powder for use as filler is well established in several industries,
but as with the cement kiln route, it reduces the value of the material to that
of calcium carbonate, which can be purchased at very low cost (around £200/tonne).
In addition, it requires a significant amount of energy input to grind the
material finely. Thus apart from some in-house recycling (see below), attempts
to commercialise this as a recycling route have failed.
In the UK two roof light
manufacturers now recycle some of their own waste by grinding. Filon Products has invested in machinery
to grind their in-house GRP waste and incorporates it into a range of products
including roofing sheet, valley gutters and flat sheet for signage. They are
now investigating using the recyclate in moulding compounds.
Hambleside Danelaw (HD) is
similarly grinding waste, and offers a take-back scheme for products at end of
life. They have been involved in trials in numerous products over the last 10
years or so. Initially they worked with Dundee University using the recyclate
in foamed concrete which had some advantages, but the reduction in slump
(effectively increased viscosity) meant that it did not flow easily into
moulds. In 2007-2008 in the UK several trials were undertaken through the BeAware
project (Built Environment Action on Waste Awareness and Resource Efficiency)
to incorporate GRP waste into precast concrete and rubber products.
Improvements in properties were demonstrated, but again results were not
commercialised.
However HD has found that there is more
value in separating off the glass fibres from the resin powder to re-use as
reinforcement. They have trialled this in new glass fibre mats for valley
gutters and also in thermoplastic composites. In addition to glass fibre
reinforced polyester products, they manufacture building products from
injection moulded polypropylene (PP) and other polymers. Adding the short glass
fibres to the PP increases strength and stiffness as well as reducing the PP
content and therefore the cost of the injection moulded products. They are
exploring ways to widen applications and so reach a place where they can take
waste from other companies to process and sell back into new products.
|
As a responsible business we feel
that we have to look at a circular economy and take responsibility for the
products we manufacture. We can’t keep throwing things into holes in the
ground, because a) there aren’t enough holes, and b) the cost of landfill is
increasing.
|
|
Ray
Khan, Director of Quality and Environmental Standards, Hambleside Danelaw
|
Ray Khan, Director of Quality and
Environmental Standards at HD, says: “As a responsible business we feel that we
have to look at a circular economy and take responsibility for the products we
manufacture. We can’t keep throwing things into holes in the ground, because a)
there aren’t enough holes, and b) the cost of landfill is increasing.”
Similar work has been done by Mixt
Composites Recyclables (M-C-R) in France, a
subsidiary of Plastic Omnium Auto Exterieur. M-C-R manufactures moulding
compounds and takes back process waste from its clients which is ground and
re-integrated into new compounds for automotive parts. The recyclate is finely
ground to about 50 microns to replace filler.
Sébastien Masson, R&D Project
Manager at M-C-R, explains that the added value is in the environmental aspect,
or in respecting incentives to recycle/increase recycled content.
M-C-R also extracts longer fibres
from less finely ground recyclate and sells this as a substitute for PP fibres
in cement floor screeds, where the fibres limit cracking during the early
setting of the cement. This has been validated in trials by CERIB (Centre
d’Etudes et de Recherches de l’Industrie du Béton). They have also done some
studies compounding the fibres in thermoplastics, though this is not yet
commercially active.
In Belgium, Reprocover manufactures
manhole covers, valve chambers and other construction products using ground
thermoset industrial waste including GRP and clean waste fibres from nearby
glass fibre reinforcement manufacturer, 3B-the
fibreglass company. They have recently developed a bi-block railway
sleeper with excellent vibration absorbing qualities which is currently
undergoing detailed testing for approval to replace timber railway sleepers.
Timber railway sleepers are likely to be phased out in Europe due to
legislation which is expected to come into force in 2018 relating to the
carcinogen effect of the creosote used to treat them, so railway companies are
actively seeking alternatives. This could be a useful growth market application
for waste GRP. ♦
Part 2 of this article will be
published next month.
Further
information
Stella Job is a Knowledge Exchange
Expert for the Materials Knowledge Transfer Network (KTN). The Materials
KTN is funded by UK Government’s Technology Strategy Board to support
innovation and research in materials science. Contact stella.job@materialsktn.net.
To keep in touch with Materials KTN activities in this area, join the Composite
