Formed from the remains of trees, ferns, algae, and other plants that lived millions of years ago, coal was the first fossil fuel actively used by humans. Coal has been used for centuries to cook food, heat homes and businesses, fuel furnaces and forges, power the steam engines of locomotives and ships, and more. Coal is the primary source of energy used in the United States (which leads the world in oil consumption), although its usage has decreased in recent years. In 2008, coal was used to generate 50% of the country's electricity, but that percentage had fallen to approximately 31% by 2016.
Despite its still-high level of consumption, the United States has enough coal to last approximately three hundred years at current usage rates. However, coal is the "dirtiest" of the fossil fuels, known to release significant amounts of greenhouse gases and other air pollutants when burned. As such, the United States is actively seeking to decrease its reliance on coal, leave behind its status as one of the world's biggest greenhouse gas emitters, and become one of the world's leading producers and consumers of renewable energy.
At first glance, it seems obvious that the world's most populous countries and highest overall energy consumers would also use the largest amount of coal. However, when broken down into per capita usage, which divides the total usage by the number of people living in the country, the list of most coal-dependent countries changes significantly.
Coal emits the most pollutants of any fossil fuel, making it the dirtiest of all commonly used energy sources. When burned, coal releases numerous airborne toxins and copious amounts of carbon dioxide (CO₂), the most prominent greenhouse gas. Climate experts calculate that the use of coal, primarily in power plants generating electricity, is responsible for 30% of all global warming. Data such as this has prompted the majority of the world's countries to attend international meetings such as the 2021 COP26 climate summit in Glasgow, Scotland, and pledge to reduce their coal use as part of a global shift toward cleaner energy.
China consumes the most coal in the world, with 4,320 trillion MMcf.