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UK first as sewage used in cement manufacture

TRIALS OF processed sewage sludge as fuel for cement manufacture begin next week at a works in Staffordshire - a first for the UK.

Producer Lafarge intends to replace part of the coal and petroleum coke used to fire the kiln at its modern Caudron works with processed sewage pellets (PSPs).

These are said to have a calorific value around two thirds that of coal, and to produce no unacceptable emissions.

'We have invested nearly £2M in a system for unloading the pellets, storing them and feeding them into the kiln, ' a Lafarge spokesman said on Tuesday. 'PSPs have been heat treated, and are as harmless as garden soil. Many other countries around the world use PSPs as cement fuel, and have done so for years.'

The six month trials will be monitored by the Environment Agency, which gave permission for Caudron to use up to 20,000t per annum of chipped tyres as fuel five years ago.

A Lafarge spokesman said the use of chipped tyres had cut oxides of nitrogen (NOx) emissions at Caudron by a third and had been accepted by local residents.

He expected further NOx reductions from the addition of PSP to the current coal, coke and tyre chip mix, as well as the saving of up to 20,000t of fossil fuels annually.

Temperatures in cement kilns top 1,400 0C, completely destroying complex hydrocarbons and binding any heavy metals present in the fuels into the cement clinker.

Experience over the last few years has shown that tyres burn without smoke at such high temperatures, and it is claimed that burning PSPs will not produce any distinctive odours.

Dave Parker INFOPLUS www. cement. bluecircle.co.uk

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