Sir - Oxfordshire County Council has reduced its shortlist of companies bidding for its 25 year waste treatment contract to only proposals for incineration (Report, December 21). The documents for the forthcoming county council debate make interesting reading; while commercial and technical factors are part of the selection criteria, environmental concerns, for example greenhouse gas emissions - which contribute to global warming, don't score.

That the moral and ethical considerations of global warming aren't a consideration must be of concern. However neither is the Council considering the possible financial costs of greenhouse gas emissions, or carbon emissions as they're known, from its new waste treatment.

Central government is now calculating a notional shadow price for carbon and including this in its financial costings of major infrastructure projects 1. The 2007 price for emissions is £25.50 a tonne of carbon, rising to £59.60 a tonne by 2050. A cursory calculation, assuming one tonne of rubbish emits one tonne of carbon when burnt, for a 200,000 tonne incinerator, shows the carbon cost in 2007 to be £5.1m. While Oxfordshire County Council may think fit to ignore this cost now, it's surely not credible to ignore its cost in the forthcoming 25 years. The agreement by the governments from around the world at Bali in December 2007, for deep cuts in greenhouse emissions, and the Climate Change Bill with its 80 per cent cuts in greenhouse gases by 2050 should give confidence to the likely pricing of carbon emissions.

We advocate the use of Mechanical Biological Treatment, particularly using anaerobic digestion, for our waste treatment. This process produces considerably less greenhouse gases than incineration. Perhaps the County Council, with its concern for lower taxes, should take note.

Andrew Wood, Oxford Friends of the Earth, Oxford