Alliant Energy has announced its intention to stop using coal as its energy source in Burlington by 2021.The Burlington Hawk Eye reports that Alliant and Burlington city officials met Friday to make the announcement.Alliant spokesman Justin Foss says the move is a step toward improving the environment.The Alliant Energy Burlington Generating Station is located on the south part of town. Foss had no figures on how much coal is burned there now. He says the company’s plan is to replace coal with natural gas.Foss also says rates will not be affected by the change, and customers “won’t see any impact.”Some of Alliant’s larger generating plants already have converted to natural gas, including those at Dubuque and Marshalltown.