Credential Tyres Fuel Successful Tarmac Trials

The trial use of tyre chips as an alternative fuel in the high temperature cement kiln at Tunstead Quarry, near Peak Dale, Buxton, has been “a resounding success,” according to Credential Environmental. The kiln operator, Tarmac Buxton Lime and Cement, says the equivalent of 2 million old tyres have now been used and the trial has demonstrated that using tyre chips gives significant environmental benefits, including a reduction in the use of fossil fuels and a 15 per cent cut in emissions of oxides of nitrogen (NOx).

All of the ‘Critical Success Factors’, set by the Environment Agency for the trial, have reportedly been met. “It’s good news for the local environment and also for wider society as fossil fuel consumption has been reduced while a beneficial use has also been found for a waste which was previously disposed of in landfills”, says Hasan Bobat, Fuels Development Manager.

Steve Patterson, director of Credential Environmental, who provided the tyres, said: “This promises to be an exciting breakthrough for the recycling of used tyres and we’re delighted to be collaborating with Tarmac on the trials.”

The trial, closely supervised by the Environment Agency, was carried out in the latter part of 2006 and early 2007. Monitoring methods compared plant emissions when using conventional fuels, coal and petroleum coke, with replacement of up to 50 per cent of heat requirements with tyre chips. As the trial was a success the company is allowed to continue using the substitute fuel while the Environment Agency considers the trial results in detail.

A 79-page trial report, backed up by thousands of pages of monitoring data, has been sent to the Environment Agency who will go through the report before deciding whether to give permanent permission for the use of tyre chips at Tunstead.

The tyre chips are supplied by Newton Aycliffe-based Credential Environmental, a leading used tyre collection and processing company – sourced from cars and light vans only. The company recovers those that can be re-used or re-treaded at its sites in Durham, North Yorkshire and Wednesbury in the Midlands, before chipping the remainder and producing a variety of quality, tyre-derived products. These include cement kiln fuel and aggregate replacement materials that are now being used extensively in civil engineering applications.

The tyre chips are delivered by lorry to Tunstead and held in new storage facilities for safe handling before being fed at a controlled rate into the kiln calciner using a covered conveyor and replacing a proportion of the coal used previously.

The very high temperatures, long combustion times and excess air in the cement kiln ensure complete combustion of the tyre chips in the process, so there is no black smoke or smell.