Chipped tyres offer leachate drainage solution

According to the Environment Agency the UK produces 480,000 tonnes of waste tyres each year with more than 300,000 tonnes being recovered or recycled. About 145,000 tonnes are disposed of to landfill sites, and a further 16,000 tonnes are used for landfill engineering.

Legislation introduced in July 2003 means that whole tyres can no longer be disposed of at UK landfill sites. This ban will extend to chipped tyres in 2007. Consequently, alternative uses must be found for scrap tyres. Burning chipped tyres in cement kilns is just one possibility. It has the added advantage of helping to conserve the fossil fuels, like coal, which have been traditionally used in cement-making.

In a recent move, the Agency has confirmed that Castle Cement will be allowed to burn chipped tyres as a substitute fuel at its Ribblesdale works, replacing some of the coal needed to heat one of the company's kilns.

Landfill drainage

In another recent, and potentially significant, development, used tyres could be given a new lease of life following tests being carried out by SLR Consulting on behalf of Credential Environment -a leading collector and disposer of tyres in the UK.

Following research and development carried out by SLR, the companies are investigating using chipped tyres as leachate drainage blankets in landfill sites. The project is in response to the Government's implementation of the aggregate levy and its initiative to reduce the use of primary aggregates - gravel is often used for this purpose - by encouraging the use of recycled materials.

Initial research and laboratory tests were carried out to test the hydraulic performance of such a blanket under increasing waste loads. The results showed that chipped tyres are a realistic alternative to aggregates although there were some unresolved issues relating to the use of a tyre drainage blanket installed over a geo-membrane.

This led to a full-scale field trial on a 8,000 m2 cell at Biffa's Roxby Landfill site in Scunthorpe, Lincolnshire, which began in September 2003. The site is being closely monitored to measure the permeability, compression of the chipped tyre material during placement of waste, and the performance of drainage pipes laid within the blanket. Findings to date are extremely positive and surveys will continue. Waste is scheduled to be placed in the cell this spring. Credential Environment's products have already been successfully approved and used on mineral lined sites in various regions and for a number of landfill operators in 2002 and 2004.



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