There is still little consensus in the industry about the value of carbon footprint labelling on food and drink as a useful means of driving more sustainable consumer choices.
Food manufacturers and retailers attending The Guardian newspaper's climate change summit last month all agreed that measuring carbon footprints could help cut emissions and costs. But the best way of communicating this to consumers is still hotly debated.
One industry source told Food Manufacture: "There is no real consensus. One problem is whether you are comparing like with like. Is it fair to compare the carbon footprint of a 100g chocolate bar with a 60g bar?"
Coming up with a category average against which individual products could be compared was also fraught with difficulties, he added. "It's a minefield once you start looking at it in detail."
However, Tesco sustainability manager Katherine Symonds said the labels would "almost certainly evolve as more products are measured". While it was helpful to identify some units for benchmarking purposes - for example, 250ml of juice, or 'per wash' for detergent - this was not always appropriate, she said. "Some people just want to compare one loaf with another."
However, when footprinting work had been done across a whole category, it "might make sense to present the category average", she added.
PepsiCo UK had introduced carbon footprint labels on Walkers crisps and was now measuring the footprint of products under the Quaker and Tropicana brands, said head of corporate responsibility Andrew Smith. "As so few products currently have labels, consumers just see them as stickers showing you've made a commitment to reducing your carbon footprint. But once more are labelled, it will be possible to compare."
Coca-Cola Enterprises (CCE) public affairs chief Erika Coghlan said: "The biggest issue for us as a multinational business is selecting something that will work across multiple markets."
Paul Monaghan, sustainable development director at the Co-operative Group, added: "Measuring your carbon footprint is vital, but whether you put this on the label is a different matter."
Euan Murray, carbon footprint general manager at the Carbon Trust, said: "Ironing out these problems over labelling is complex, but it doesn't mean it's not worth doing. Along with the government and the British Standards Institute, we've been working with hundreds of organisations outside the UK to try and ensure that we have something that can be agreed internationally."