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Coal, produced over millions of years, is a finite and non-renewable resource on a human time scale. A non-renewable resource (also called a finite resource) is a natural resource that cannot be readily replaced by natural means at a pace quick enough to keep up with consumption. [1] An example is carbon-based fossil fuels.
During the 20th century, energy consumption rapidly increased. Today, about 80% of the world's energy consumption is sustained by the extraction of fossil fuels, which consists of oil, coal and natural gas. [4] Another non-renewable resource humans exploit is subsoil minerals, such as precious metals, mainly used to produce industrial commodities.
Renewable energy alternatives also exist. These include solar energy, wind energy, geothermal and hydroelectricity as well as other sources. These sources are said to have much lower emissions, and almost minimal secondary by products. The production of renewable energy is projected to grow in nearly every region in the World. [78]
To become a zero-carbon city, renewable energy must supersede other non-renewable energy sources and become the sole source of energy, so a zero-carbon city is a renewable-energy-economy city. Transitioning to a zero carbon city means examining the generation of power sources, such as renewable electricity and decarbonising electricity production.
Sources of water pollution are either point sources or non-point sources. [155] Point sources have one identifiable cause, such as a storm drain, a wastewater treatment plant, or an oil spill. Non-point sources are more diffuse. An example is agricultural runoff. [156] Pollution is the result of the cumulative effect over time.
The role of non-renewable energy sources in sustainable energy is controversial. Nuclear power does not produce carbon pollution or air pollution, but has drawbacks that include radioactive waste , the risk of nuclear proliferation , and the risk of accidents .
Energy has been harnessed by human beings for millennia. Initially it was with the use of fire for light, heat, cooking and for safety, and its use can be traced back at least 1.9 million years. [4] In recent years there has been a trend towards the increased commercialization of various renewable energy sources.
Carbon dioxide emissions from the production of shale oil and shale gas are higher than conventional oil production and a report for the European Union warns that increasing public concern about the adverse consequences of global warming may lead to opposition to oil shale development. [1] [3] Emissions arise from several sources.