Independent: Britain’s biggest supermarkets say they are on course to reduce by half their use of plastic bags by Easter. Tesco, Asda, Sainsbury’s and Waitrose are making progress in cutting the number of free bags handed out to shoppers at the checkout. Plastic bags are made using oil and take hundreds of years to degrade in landfill sites, often after a single use. An estimated 13 billion plastic bags are handed out by UK retailers every year. In February last year, six trade associations …