Solid fuel purposes, such as refining metals. Coal is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide anthropogenic sources of carbon dioxide releases. The extraction of coal, its use in energy production and its byproducts are all associated with environmental and health effects including climate change. Variations such as smokeless coal can be formed naturally in the form of anthracite, a metamorphosed type of coal with a very high carbon content that gives off a smokeless flame when set alight. Coke is a fuel with few impurities and a high carbon
Coal pollution mitigation industry. Complaints focus on the environmental impacts of coal extraction, high costs to sequester carbon, and uncertainty of how to manage end result pollutants and radionuclides. In reference to sequestration of carbon, concerns exist about whether geologic storage of CO in reservoirs, aquifers, "etc.", is indefinite/permanent. The palaeontologist and influential environmental activist Tim Flannery made the assertion that the concept of clean coal might not be viable for all geographical locations. Critics also believe that the continuing construction of coal-powered plants (whether or not they use carbon sequestration techniques) encourages unsustainable mining practices for coal, which can strip away mountains,