It might be an idea whose time has come – shop and save the planet. In the UK, online shoppers can now build up credits to offset their annual carbon footprint. A new portal, Smartly Green, allows shoppers to click through to the web sites of major High Street retailers like John Lewis, Asda and Comet. When they make a purchase, Smartly Green receives a commission from the retailer. Of the commission, 50% isreturned to the shopper. But here’s where it differs from most loyalty schemes. 80% of the amount due to the shopper is given to PURE, a carbon-offsetting charity that’s compliant withthe Kyoto Treaty. The remaining 20% goes to the shopper in cash. Once a shopper has offset his annual carbon footprint (which you can calculate through Smartly Green, then the figures arereverse, with 80% returned to the shopper and 20% going to PURE. As a rough guide, Smartly Green estimates that a family of four living in a detachedhouse, owning two cars and taking one flight to Europe and one long-haul flight per year will emit about 16 tonnes of CO2. As an average, each $600 spent via Simply Green will generate enough incommission to offset 0.5 tonnes of carbon. That means spending over $19,000 a year via Smartly Green to offset the family’s emissions – and that’s quite a chunk of change, and meansthat most people won’t be seeing a lot of cash returned to their wallets. However, for ethical shoppers, it might represent a step in the right direction.