Story : With food thought to account for at least 20 per cent of the UK's greenhouse gas emissions, our grocery basket can have a big impact on our environment. Greenpeace say British supermarkets are producing about 900,000 tons of plastic packaging every year. That means if they go 'green', so do we. Jonathan Maitland examines the Green credentials of Britain's biggest supermarkets, and asks what we can do as consumers to play our part?