Fluidized-bed combustion (FBC) is a method of burning coal that reduces the amount of sulfur that is allowed to escape the power plant in the form of SOx emissions. This approach uses limestone to precipitate out sulfate during combustion, which has the added perk of allowing more efficient heat transfer from the boiler to the apparatus used to capture the heat energy (usually water pipes) due to the heated precipitate coming in direct contact with the pipes (heating by conduction), allowing greater efficiencies. Since this allows coal plants to burn at cooler temperatures, less NOx is also emitted. FBC boilers can burn fuels other than coal, and the lower temperatures of combustion (800 degrees C) have other added benefits as well.