The Borough of Islington in London has devised a plan to use excess, otherwise-wasted thermal energy generated by the London Underground to heat hundreds of homes and buildings. The move would cut emissions, increase efficiency, and save residents money on heating bills. Islington has a district heating network, which is more efficient than individual furnaces or boilers, as the system distributes heat and hot water from a centralized location through insulated pipes. While these types of systems have been around for a while, they have often been powered by fossil fuels. New York City has one of the world’s largest systems, but it’s fueled by natural gas and fuel oil. As cities look for alternative energy sources, a few have even turned to waste heat from sewage to heat their cities. “We don’t really need to burn gas at 1,000 degrees centigrade [1,832 degrees Fahrenheit] to get your bath to 30 degrees centigrade. What we need to do is work with nature to optimize the use of heat,” said Jon Gluyas, a professor of earth sciences at Durham University. (New York Times $)