Illustration for NewScientist / UK of last week. Pee-n-grow : Manufacturing artificial fertiliser is a highly energy intensive process that consumes roughly 1 per cent of the world's energy supply. As odd as it sounds, using sterile, nitrogen-rich human urine instead could prevent the emission of more than 180 million tonnes of C02 each year. Urine collection systems with basement storage tanks have been built by the Stockholm Environmental Institute in more than 800 apartments in rural China, saving an estimated 20 tonnes of C02 emissions annually. Make sense?