al is a combustible black or brownish-black sedimentary rock, formed as layers called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. It is a fossil fuel, formed when plants decay into peat which is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits formed from wetlands called coal forests that covered much of the tropics during the late Carboniferous and early Permian. Coal is used primarily as a fuel. While coal has been known and used for thousands of years, its usage was limited until the Industrial Revolution. With the invention of the steam engine, coal consumption increased. In 2020, coal supplied about a quarter of the world's primary energy and over a third of its electricity. Some iron and steel-making and other industrial processes burn coal. The extraction and burning of coal damages the environment and human health, causing premature death and illness, and is the largest source of carbon dioxide contributing to climate change. Over fifteen billion tonnes of carbon dioxide were emitted by burning coal in 2024, which was more than a quarter of total global greenhouse gas emissions.As part of worldwide energy transition, many countries have reduced or eliminated their use of coal power. The United Nations Secretary General asked governments to stop building new coal plants by 2020. A record amount of coal was burnt in 2024, but consumption is expected to peak before 2030. To meet the Paris Agreement target of keeping global warming below 2 °C (3.6 °F) coal use needs to halve from 2020 to 2030, and "phasing down" coal was agreed upon in the Glasgow Climate Pact. The largest consumer and importer of coal is China, which mines almost half the world's coal, followed by India with about a tenth. Indonesia and Australia export the mo