As if product labelling were not already complicated enough, shoppers are now being exhorted to study the carbon footprint of their favourite brands.

Those of us who have only recently begun paying attention to the fat, sugar and salt content of foods or contemplating the fair-trade option are being asked to grapple with a whole new statistic: the grams of carbon dioxide emitted throughout the life of a product — from field to shelf to plate to bin.

No longer will you be able to slurp pure, squeezed Tesco orange juice with a guilt-free conscience. Study the black footprint symbol on the carton and you will learn that you are destroying the planet more than twice as fast as you would have had you chosen long-life juice, which is made from concentrate.

The footprint of pure, squeezed juice is 400g of carbon dioxide equivalent per 250ml serving, while that of long-life is only 150g. The main reason for the difference is that pure squeezed juice has to be kept refrigerated. The CO2 emitted in transporting it is also much higher than for concentrate.

If a significant number of people could be persuaded to sacrifice that pure-squeezed taste for the sake of polar bears or the low-lying Maldives, footprint labels would unquestionably be deemed a good thing. Every little helps and thinking about the carbon footprint of what we buy helps to prepare us for the much more profound changes in habits needed to attain a low-carbon lifestyle.

However, in the two years since the government-supported Carbon Trust launched the footprint logo, the companies that adopted it have seemed more interested in exploiting it as a marketing opportunity than in its carbon-saving potential.

PepsiCo, which in 2007 made a big fanfare of signing up to the scheme, has calculated the carbon footprint of its Tropicana orange juice but does not display the figure on cartons in the UK. Companies are nervous about enabling shoppers to compare the carbon footprint of rival products.

In this instance that could mean own-brand lines of juice from Tesco, some of which carry the footprint logo. Of course Tesco is happy to enable comparisons among its own products: whichever you choose, Tesco gets the sale.

The Carbon Trust says that it wants to see the footprint logo on all products “eventually”, though it will not give a deadline. It adds: “We don’t think we are ready yet for that cut-throat cross-brand competition.”

Tesco has now put the logo on more than 100 of its own-brand products, including light bulbs, milk and detergents, yet there are curious gaps within product families. With milk, customers can choose from a pint of skimmed (700g of CO2), semi-skimmed (800g) or full-fat (900g). Organic milk, however, has no footprint information even though people who buy organic tend to be more concerned about the environment.

Tesco says it has not yet calculated the footprint of its organic milk, though it will not explain why. But according to research by Judith Capper, now at Washington State University, organic milk has a bigger carbon footprint than ordinary milk as organic farming is less intensive.

Other companies have successfully lobbied the Carbon Trust to weaken the footprint scheme by allowing them to display the logo without any figure for CO2. Loaves of Kingsmill bread, for example, have the logo on five sides of the wrapper, but the emissions statistic is hidden in the small print.

The trust says that use of the logo signifies a commitment by manufacturers to reduce emissions, and that this is more important than the actual amount of CO2 their products generate. It adds that companies that fail to reduce emissions over a two-year period will no longer be allowed to display the logo. Yet no target reductions have been set: a company that cuts emissions per product by a mere 0.1 per cent in two years could keep using the logo. At that rate, the Maldives are sunk.

Consumer Focus, the government-funded watchdog, says carbon labelling is a side issue and that retailers who genuinely want to help customers to make greener choices should take the most environmentally damaging products off the shelves.

Clearly a balance needs to be struck between reducing emissions and offering reasonable consumer choice. People who like pure squeezed orange juice would be kicking and screaming if forced to drink concentrate. But supermarkets could take simpler steps that would cut CO2 without shoppers feeling they were losing out.

Tesco sells two kinds of made-from-concentrate juice. The main difference between them is not in quality, taste or nutritional value but simply that one version comes ready-chilled. Emissions for the chilled version are 60 per cent higher than for unchilled. If Tesco were serious about helping to save the planet, it would stop selling chilled concentrate.

Ultimately the best way to encourage climate-friendly shopping habits would be to attach a fair, global price to emissions so that products with bigger carbon footprints cost more. Then shoppers could stop poring over labels and start focusing on enjoying the things they could still afford. •

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