Letter: Left cold by waste

Sir: I shared Philip Williams's enthusiasm (Letter, 13 May) for the Deptford incinerator until I visited it and studied its specification. My disillusion began with the discovery that this is not a Combined Heat and Power (CHP) plant. It uses air-cooled condensers, thus throwing away any possibility of recovering the waste heat.

What it can do, much less efficiently, is to divert some of the steam from electricity generation to provide district heating. At the very best this might give 60 per cent efficiency, as compared with 85 per cent theoretically possible from CHP.

Taking the calorific value of municipal solid waste to be one third that of coal, the efficiency of the electricity generation at Deptford works out at 25 per cent compared with the 35 per cent obtained from the best coal- and oil- burning power stations. Such stations obviously have to pay for their fuel.

My second shock was finding that the local authorities of south- east London, having incurred all the expenses of collecting the 'fuel', then have to pay the operators pounds 20 a ton to accept it. Whether or not a case can be made for plants like Deptford on environmental grounds, there is clearly no economic case.

Yours faithfully,

ROBERT JAMES

Southsea, Hampshire