8.2 Energy resources

Energy resources and their uses: coal

The products of the lithosphere are also important in meeting our energy needs . Coal is one product that is used to produce energy. In South Africa, coal is particularly important because most of our electricity is generated using coal as a fuel. South Africa is the world's sixth largest coal producer, with Mpumalanga contributing about 83% of our total production. Other areas in which coal is produced, include the Free State, Limpopo and KwaZulu-Natal. One of the problems with coal however, is that it is a non-renewable resource , meaning that once all resources have been used up, it cannot simply be produced again. Burning coal also produces large quantities of greenhouse gases, which may play a role in global warming. At present, ESKOM, the South African government's electric power producer, is the coal industry's main customer.

The formation of coal

Coal is what is known as a fossil fuel . A fossil fuel is a hydrocarbon that has been formed from organic material such as the remains of plants and animals. When plants and animals decompose, they leave behind organic remains that accumulate and become compacted over millions of years under sedimentary rock. Over time, the heat and pressure in these parts of the earth's crust also increases, and coal is formed. When coal is burned, a large amount of heat energy is released, which is used to produce electricity. Oil is also a fossil fuel and is formed in a similar way.

Fossil Fuel

A fossil fuel is a hydrocarbon that is formed from the fossilised remains of dead plants and animals that have been under conditions of intense heat and pressure for millions of years.

How coal is removed from the ground

Coal can be removed from the crust in a number of different ways. The most common methods used are strip mining , open cast mining and underground mining .

1. Strip mining Strip mining is a form of surface mining that is used when the coal reserves are very shallow. The overburden (overlying sediment) is removed so that the coal seams can be reached. These sediments are replaced once the mining is finished, and in many cases, attempts are made to rehabilitate the area.
2. Open cast mining Open cast mining is also a form of surface mining, but here the coal deposits are too deep to be reached using strip mining. One of the environmental impacts of open cast mining is that the overburden is dumped somewhere else away from the mine, and this leaves a huge pit in the ground.
3. Underground mining Undergound mining is normally used when the coal seams are amuch deeper, usually at a depth greater than 40 m. As with shaft mining for gold, the problem with underground mining is that it is very dangerous, and there is a very real chance that the ground could collapse during the mining if it is not supported. One way to limit the danger is to use pillar support methods, where some of the ground is left unmined so that it forms pillars to support the roof. All the other surfaces underground will be mined. Using another method called longwalling , the roof is allowed to collapse as the mined-out area moves along. In South Africa, only a small percentage of coal is mined in this way.