natural gas
definition
Natural gas is a colourless, odourless mixture of a number of gases, mostly methane. Australia has relatively high supplies of natural gas especially in areas of Victoria, Central Australia and Western Australia. It is expected that Australia's current natural gas reserves will last until 2050, possibly longer if more reserves are discovered. Although it is naturally found as a gas it can be liquefied at -161°C. Over 20 per cent of the world's energy is derived from natural gas and Australia is the fifth largest exporter of liquefied natural gas. Although it is not commonly used to generate electricity, its popularity is growing.
how natural gas works
Natural gas is created from the remains of plants and animals that lived millions of years ago. The pressure of the earth's surface changed them into fossils. Coal is a solid form of compressed remains, while natural gas is a gaseous version. The gas is reached by drilling through deep into the earth's surface. It is put into a combustion chamber and from there compressed air is forced into the chamber and makes what is known as combustion gas. This hot gas expands through the turbine and drives a generator which creates electricity.
advantages of natural gas
There are several advantages from using natural gas to generate electricity:
- It is relatively cheap
- Natural gas generators are small in comparison to other types of generators
- Gas produces half the carbon dioxide of coal or oil
- It is easy to store and can be safely transported over long distances
disadvantages of natural gas
However, natural gas has the following disadvantages:
- It is not a renewable form of energy
- Although it is a cleaner form of energy than coal, it still produces carbon dioxide and therefore contributes to global warming
- There are only limited supplies of natural gas in the world
coal seam gas
definition
Coal seam gas (CSG) is an odourless, colourless natural gas created over millions of years as a by-product while organic matter is turned into coal. This gas, mainly comprising methane, is trapped on the surface of the coal. Australia has sizeable quantities of this resource, mainly in Queensland and NSW. Although it is not currently widely used throughout the country, there is a lot of research looking at this method's potential to contribute to Australia's energy supply. Queensland is the country's largest consumer of CSG, comprising more than 70% of the state's gas supplies.
how coal seam gas works
As coal is formed, methane, carbon dioxide and water are generated. While most of these gases and water escape naturally, some of it is trapped in the coal seam. The gas is extracted through the removal of the water which is contained within the coal seams. When this water is released, the gas is also discharged. Just like with other gases, CSG can be used to drive turbines and create electricity.
advantages of coal seam gas
There are several advantages from using coal seam gas to generate electricity:
- CSG is one of the cleanest of fossil fuels
- It is relatively inexpensive
- Its production creates water as a by-product
disadvantages of coal seam gas
However, coal seam gas has some disadvantages:
- Although it is a very clean form of fossil fuel, it still releases carbon dioxide into the atmosphere
- It is not renewable - its long-term future depends upon more coal discoveries
- The water which is produced as a by-product is not yet fit for human consumption