Coal is the product of ancient plant remains that have been compacted and altered by heat and pressure over millions of years. Its formation starts within swamp ecosystems, where plants die and are subsequently covered with water and dirt. Being buried under increasingly thicker layers, the dead plant matter is tightly compacted and undergoes structural changes as oxygen, hydrogen and water migrate out of the dead material. The resulting product becomes a combustible black rock composed mainly of carbon. Today, coal is one of the most widely used energy sources and continues to be an important provider for our electrical needs.
There are two main ways to extract coal from the ground. These include surface mining and underground mining:
Surface mining: Surface mining is used when the coal is less then 60 metres underground. The top soil and rocks are removed to expose the coal. Once the mining is done, the topsoil is replaced and the area can be replanted. Surface mining is the less expensive than underground mining.
Underground Mining: Underground mining is used when coal is around 300 metres deep. Elevators and mineshafts provide pathways for miners to operate machines that dig coal.
Producing Energy from Coal
The energy within coal ultimately comes from the sun; the sun provided energy for ancient plants to grow and eventually form coal. Thus, energy has been conserved during the coal formation process. This conserved energy now exists between the chemical bonds forming coal. If the chemical bonds of coal can be broken, energy can be released. However, in order to obtain energy from coal by breaking the chemical bonds, energy is required to "activate" this process. Therefore, coal needs heat energy in order to sever the chemical bonds of coals and release its energy.
Coal plants grind coal into a fine powder. A burner combusts the coal, while a precipitator and scrubber remove any impurities and exhaust gas. Heat from the combusted coal is used to turn water to steam, which turns a turbine. The spinning motion from the turbine turns a generator, which produces electricity.
Coal is Canada's largest fossil fuel resource. In the provinces of Alberta, Saskatchewan and Nova Scotia, coal accounts for 70% of electricity needs. In rapidly growing countries such as China and India, coal provides 75%-80% of electric power. Coal continues to be a valuable energy resource, although questions are being raised about its sustainability in the future as a non-renewable resource, as well as its environmental effects. Despite these concerns, coal technology continues to advance and strive to reduce emissions while increasing efficiency.