RENEWABLE energy is any source of energy that can be used without depleting its reserves. These sources include sunlight or solar energy and other sources such as, wind, wave, biomass and hydro energy. These later sources are indirectly derived from solar energy. Biomass refers to any recently produced organic matter. If the organic matter was produced sustainably then it is considered to be a renewable energy resource.

Fossil fuels such as coal, oil and gas come from biomass which was produced in the distant past and has been transformed by geological activity. World reserves of fossil fuels are finite and are being depleted. They are, therefore, referred to as non-renewable energy resources.

Uranium for the generation of nuclear energy is not a fossil fuel, but still requires the depletion of finite physical reserves so it is included as a non-renewable energy source. Some geothermal resources may be regarded as renewable because they are derived from energy sources deep within the earths interior. The energy sources is so large that the rate of depletion by a geothermal energy extraction project is negligible. Projects based on using the remnant heat stored in shallowly placed igneous rocks may be non-renewable. However, the use of energy from such sources does not produce greenhouse gases.

Another renewable resource, tidal power results from harnessing tidal currents which are caused mainly by the gravitational pull of the moon on the oceans as it circles the earth.

Why is renewable energy important?

When fossil fuels are burnt to release energy, they also release carbon dioxide to the atmosphere. Carbon dioxide is the main greenhouse gas that contributes to global warming.

Biomass is the only renewable energy source that releases carbon dioxide in use. However, the carbon dioxide emitted in use is balanced by the incorporation of carbon from the atmosphere into the biomass while the biomass is growing. If the biomass resource is being used sustainably, there are no net carbon emissions over the time frame of a cycle of biomass production. This could be a year for an agricultural crop waste such as bagasse or decades for forest products. In addition minor amounts of greenhouse gases may be created in producing the technology to transform the renewable energy resource into useable energy.

Because the use of renewable energy creates so little greenhouse gas emissions, the use of renewable energy is an important part of the world’s response to the enhanced greenhouse effect.

— Excerpts from Australia’s Renewable Energy website