Global bottled water giants are ramping up trials of easily recyclable aluminum cans to replace plastic that pollutes the worlds seas. This may sound like a slam-dunk for the environment. Aluminum cans might indeed mean less ocean waste, but they come with their own eco-price: the production of each can pumps about twice as much carbon into the atmosphere as each plastic bottle. French group Danone has become the latest company to make a move, telling Reuters it had started to replace some plastic bottles with aluminum cans for local water brands in Britain, Poland and Denmark. The shift, previously unannounced, comes as multinational rivals like Coca-Cola Co, PepsiCo and Nestle are also launching some canned versions of water brands. The beverage industry has been scrambling to react to public anger over scenes of huge piles of plastic waste contaminating oceans, pledging to step up recycling efforts. However, its not black and white on the green front. By increasing recycling via cans, companies could fall back in efforts to reduce their carbon footprints, illustrating the tough juggling act they can face to keep environmentally conscious investors, campaigners and consumers on-side. Ruben Griffioen, sustainability manager of packaging materials at Heineken, said "thats the dilemma youre going to have to choose between," adding the company was trying to reduce both plastic waste and emissions. At aluminums most polluting level, a 330 ml can is responsible for 1,300 grams of carbon dioxide emissions, according to the analysis compiled for Reuters, roughly equating to the emissions produced by driving a car 7 to 8 km. A plastic bottle of the same size, made from the polyethylene terephthalate (PET) plastic typically used, accounts for up to 330 grams. So aluminum has a larger footprint in production because of the vast power needed in the smelting process. But, in a further example of the complexities of environmental impact, the overall carbon equation becomes more muddied when other issues such as logistics are taken into account.