United Utilities and Severn Trent, Britain’s biggest publicly traded water companies, are increasingly feeding human waste into tanks of bacteria whose methane emissions generate electricity.Sewage-derived power supplies 22 per cent of Severn Trent’s energy, almost double that of 2005. At United Utilities, it’s 14 per cent. British utilities are shifting fecal matter to vats of bacteria that consume the waste, releasing biogas that’s burned to drive water treatment. The result is lower energy bills and surplus power sent to the grid that heat more U.K. tea kettles.Water businesses in Britain aren’t the only ones finding value in waste. Companies in Europe and China are turning more to biogas to counter fossil-fuel costs and energy price volatility. Microsoft, the largest software maker, uses effluents to help power a data center in Wyoming. Skiers in northern Arizona speed down slopes on artificial snow made entirely from treated wastewater.“We live in a resource-constrained world, we’re going to have to squeeze more and more out of our waste,” said Christopher Gasson, the publisher of Global Water Intelligence in Oxford, England. Sewage sludge “smells like money to an increasing number of entrepreneurs.”AdvertisementSome investors in Europe see an opportunity in such a market. Last year, Bayerische Motoren Werke AG heiress Susanne Klatten, Germany’s wealthiest woman, bought 20 per cent of Paques BV, a Dutch biogas technology business.