Freeze frame
Guy Robinson
Simon Baggott
Tyre remanufacturing, step by step
A four-way partnership project in South Wales is taking the lead in the processing of shredded rubber. Thanks to cryogenics, your used tyres could end up surfacing a sports stadium near you. By Simon Baggott and Guy Robinson
Over 46 million used tyres are generated annually in the UK, reports the Waste & Resources Action Programme (WRAP). And while the tabloid image of mountains of burning tyres may be a thing of the past, it remains etched in the minds of some stakeholders as a practice to be both feared and avoided.
A new recycling facility - believed to be the first of its kind in northern Europe - takes a different approach. The plant at Baglan, near Port Talbot, South Wales, opened on 25 July and uses a new cryogenic process in which shredded tyres are frozen and shattered into rubber ‘crumb’. The TyreGenics plant plans to reprocess 4 million used tyres annually, thereby aiming to diminish the volume of used tyres in storage and produce commercially viable products using old tyres as the main raw material.
Project development and funding
TyreGenics is a joint venture between majority shareholder Credential Environmental, a UK market leader in recycling used tyres; industrial gases expert BOC; Canada-based artificial sports pitch business FieldTurf Tarkett; and Canadian cryogenic plant manufacturer RTI Cryogenics Inc.
Seed funding for the project came from BOC, enabling the partners to approach the Welsh European Funding Office for European Regional Development Funding. This resulted in a grant of up to £1.3 million (US$2.6 million), which translates into 35% of the capital needed for the project to progress. The consortium of partners picked up the remaining fraction of the funding needed.
The location for development was another fundamental consideration. The main reason for locating the development near Port Talbot in South Wales was the proximity to a source of liquid nitrogen. The cryogenic process relies heavily on liquid nitrogen, which would be expensive to transport at the quantities needed (about 50-70 tonnes per day). Also integral to the project were the economic benefits that would be brought to the area. It is hoped that the plant will employ up to 30 staff, which was no doubt a key benefit that stimulated support from Neath Port Talbot Council.
The plant in action
In terms of what actually happens on site, the first point to make is that the plant does not itself shred tyres. It relies on a regular supply of shredded material (see box on page 30). When the plant is fully operational, TyreGenics expects to receive a delivery about four times a day. And it has a temporary storage bunker, which can hold about 300 tonnes of material, equivalent to 3-3.5 days of production for the plant. It is important to keep the tyres dry, mainly because if they are wet, the process itself will require more liquid nitrogen.
A front loader, supplied by Manitou, is used once every 20 minutes to load material at the start of the process. Thereafter, a metal detector checks the material, and any metals can be manually removed. The material is then weighed to check throughput. Next, the shredded tyre material passes via a rotary air lock into a freeze tunnel that is 17 metres in length. The shredded tyre material is then passed down the tunnel, at the end of which the temperature is -80ºC. Cryogenics in this context is particularly useful because the output material is easier to handle than rubber crumb generated from purely mechanical processing.
Frozen chunks of material then drop down into three mills. The chunks shatter on impact with hammers that form part of these mills. A screening stage follows in which rubber drops through, fibre remains on top and steel is taken off by a magnet. About 70% of the original input material is rubber, near enough all of which is expected to be recovered.
The rubber content is then dried and a fibre scalper sorts out any oversized material, which is re-routed back into a fourth mill. A classifier separates the rubber crumb into different sizes, which are blown into different storage grades (usually contained in 1 tonne sacks).
What to do with the recycled material?
Having produced a fine rubber crumb, the next step is clearly to determine what to do with this material. And here stability is provided to the project by having a guaranteed market for 60% of the plant’s output in the shape of one of the project partners, Canada-based FieldTurf.
FieldTurf designs and manufactures the surfaces at some of the world’s most famous sporting clubs and stadiums, including the Denver Broncos and New York Jets in the US and Barcelona’s Nou Camp in Spain. The company has also installed practice grounds for the New Zealand All Blacks and many English Premiership and Championship football clubs.
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above Much of the fine rubber crumb finds a new home in sports stadiums around the world
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TyreGenics is also looking at developing a range of other applications for the remaining 40% of material it produces. These include shock pads, moulding and even material for the construction industry, for example Rubbercrete, an innovative new sound and thermal insulation and damp proofing solution. Markets for rubber crumb such as this are at an early stage in the UK, but they are developing.
As an aside, it is interesting to note that one other avenue for shredded tyres is in the generation of fuel. Indeed, Credential has undertaken a successful trial for using tyre chips as an alternative fuel in the high temperature cement kiln at Tunstead Quarry, near Peak Dale in Buxton, UK. However, in this case, the plant in Port Talbot does not rely on waste-to-energy because its aim is to produce high quality material with commercial value. This is by no means a criticism of the waste-to-energy process. TyreGenics simply sees greater commercial potential by following a recycling - or remanufacturing - route. And it seems that it is not alone in this decision (see box opposite).
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ABOVE The 17 metre freeze tunnel chills the shredded tyres to –80°C
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In terms of other products from the cryogenic process, the steel from the plant is clean compared with steel coming from many tyre recycling facilities. It receives a reasonable market price and is purchased by a local steel mill. The fibre waste from the process is the only stream that does not yet have a market. It ends up in landfill.
Tyre shredding
Before the tyre material enters the cryogenic reprocessing plant, it must be shredded. TyreGenics relies entirely on Credential Environmental for its supply. Credential has made substantial investment in its Wednesbury and Breighton sites in the UK to keep pace with the appetite of the new TyreGenics plant.
For example, what is claimed to be the world’s largest tyre-shredding machine, the Tyrannosaurus, has been installed at the Wednesbury site in the West Midlands.
The monster machine is made in Finland and was the first to arrive in the UK. It can process 3000 tyres an hour, converting them into 50-60 mm chips, and represents a significant part of Credential’s £2 million (US$4 million) investment in the Wednesbury processing operation. A substantial proportion of the plant’s output will feed the cryogenic plant.
Credential director Steve Patterson said: ‘The Tyrannosaurus is a key component in as near as you can get to a closed loop solution for the recycling of used tyres that marks an important milestone for the UK industry.’
Conclusions
Sustainable waste tyre management in the UK is gathering pace. This can be seen not only in the development of plants such as the one in South Wales, but also in supportive steps taken by WRAP.
Recycling outstrips WTE for tyre
The European Tyre and Rubber Manufacturers’ Association has published its data for 2006 indicating that more than 3.2 million tonnes of used tyres were generated in the enlarged Europe in that year. And, while retreading remains at 12% and incineration through energy recovery is stabilizing at around 32%, the major market benefiting from the landfill ban is material recycling with 34%-plus, meaning a rise of 23% over a decade. This is a signal that the slowly maturing market for end of life-derived products is sustainable and economically viable.
Furthermore, more than 87% of used tyres were treated in the EU27 plus Norway and Switzerland. The figure for the recovery rate in 2005 was 84%, indicating that the landfill Directive has been a major driver in pressing for the change.
Over recent weeks and months, WRAP has published press releases linked to its work in this area. They highlight that:
- Two new standards in the tyre recycling industry have been developed. The two Publicly Available Specifications (PAS) documents - named PAS 107 and 108 - were created in conjunction with the British Standards Institute. They provide guidance to the measures and procedures needed to produce recycled material such as shred, crumb, powder and tyre bales, to a consistent grade and quality.
- A new report provides technical information and further clarity on the indicative cost of tyre disposal, helping to break down the barriers to the secondary tyres market.
- Other research reveals that over 100,000 tonnes of steel and 17,000 tonnes of fibre could be recovered from scrap tyres generated in the UK each year. In practice, only one third of these quantities is currently recoverable. The research highlights a potential high-value application for the use of tyre-derived steel in reinforced concrete. And, in terms of tyre-derived fibre, 10 current and potential applications for it have been identified that vary from its use as a fuel to use in the manufacture of packaging material. Note that, in reality, actual uptake was found to be very limited. The study found that landfill is the most common disposal option for separated tyre fibre. Although the EU directive prohibits the disposal of shredded and whole tyres to landfill from 2006, it does not place any restrictions on putting tyre-derived fibre into landfill.
- Lastly, WRAP has updated the specialist tyres section in its website, including a series of best practice reports and case studies. For more information, visit the website at www.wrap.org.uk/construction/tyres.
This brief summary of some of what WRAP is doing is an encouraging sign. But one crucial point always needs to be borne in mind. If tyre recycling is the goal, then standards - such as PAS 107 and 108 - must be maintained for the by-products and a commercially sustainable market encouraged. This is something rather different to conventional waste disposal.
Indeed, it is worth asking the question whether what is taking place at TyreGenics can be referred to as a waste process at all.
Simon Baggott is Commercial Director of TyreGenics Limited.
email: simon.baggott@tyregenics.com
web: www.tyregenics.com
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