THE big supermarket chains are always trumpeting their carbon-reduction plans, hoping that their green credentials will attract eco-aware shoppers.

An independent report into their environmental performance, however, has found marked differences in the style and results of their plans. Some are pursuing low-carbon operations more aggressively than others , according to a study by the University of Edinburgh and the research firm Ends Carbon.

The report found disparities in retailers’ performance on energy efficiency, refrigerant gas leakage and distribution. For instance, even though Tesco is the biggest polluter, responsible for about 1.7m tonnes of carbon dioxide annually, the emissions from its heating, ventilation and cooling systems are less than half of those of some other retailers.

“It’s surprising that there is such a big difference,” said Craig Mackenzie of Ends Carbon. The research concluded that Tesco has the most ambitious carbon reduction objectives when benchmarked against Britain’s target to cut emissions 80% by 2050.

Ends calculates that meeting the UK’s goal would require a cut in emissions intensity nearing 6% a year assuming economic growth of 2.5% a year. Tesco comes the closest to this with a 5.6% target.

It is followed by the Coop, with 4%-5%. Asda and Sainsbury tie with 3.6%. M&S’s targets are equivalent to a 3.4% reduction, while Waitrose’s targets work out at less than 2% (see chart below).

Mackenzie said Marks & Spencer could beat Tesco with its commitment to become carbon neutral by 2012 and to halve its emissions of hydro fluorocarbons (HFCs), the main cooling gas used by supermarkets, by 2015. Cutting HFCs is critical because the gas has 3,000 times the global warming potential of carbon dioxide.

Mike Barry, M&S’s head of sustainable business, critisised the Ends survey, even though M&S helped to fund it. “We don’t think it’s a fair representation of our commitment to tackle our carbon footprint and nor does it consider what we are doing to tackle a much more substantial footprint associated with our supply chain,” said Barry.

He pointed out that M&S has met 39 of its 100 social and environmental commitments since the launch of “Plan A”, its environmental campaign, in 2007. This includes reducing fuel use in its delivery fleets by more than 20% and opening four eco-factories, which use 50% less energy and water.

David North of Tesco had a more positive reaction. “It’s very encouraging to be recognised as the overall top performing supermarket,” he said.

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