Coal is a combustible black sedite rock formed from prehistoric plant matter, historically used extensively for electricity generation and heating. Coal burning releases large amounts of carbon dioxide (contributing to climate change) and air pollutants affecting health and environment. Canada has phased out coal-fired electricity generation in many jurisdictions, with federal regulations requiring closure of coal plants or conversion to cleaner fuels. Alberta and Saskatchewan have been transitioning coal plants to natural gas or renewable sources. Coal mining communities face economic challenges as the industry declines. While some coal remains used for steel production, thermal coal for electricity is disappearing from the Canadian energy mix.