Energy: Past, Present, and Future Summary

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After food, air and water, energy is the most basic need of human beings for survival. Without it we could not cook, provide heating or cooling, move from place to place, and could not have achieved any of the technological advances of the present time. The unprecedented economic growth of the past century was made possible only by the availability of vast resources of cheap petroleum. At the present time we are relying primarily on the following sources for satisfying our energy needs:

• Fossil fuels provide roughly 80% of total global consumption. Fossil fuels are, however, associated with many environmental problems such as global warming, ozone depletion, acid rain, and toxic air pollutants such as oxides of nitrogen, sulfur, and carbon.

• Nuclear energy is responsible for about 6.6% of the world’s total consumption. However, it generates radioactive and toxic wastes that can remain for a very long time.

• Hydroelectric and biomass energy constitute 7% of total consumption. Hydroelectricity has relatively minor environmental impact and is renewable. Biomass is mainly in the form of wood and is renewable as long as it does not result in deforestation of existing forests.

• All the other forms of energy including solar, wind, and geothermal make up only between 1-2% of the total energy consumption.

With an expected increase in consumption of fossil fuels, we would also expect an increase in the rate of carbon emission into the atmosphere. As petroleum and natural gas reserves dwindle, coal will probably be the ultimate source for their replacement. When burned, coal, peat, and other solid fuels produce more emissions per unit amount of heat than petroleum or natural gas. They are also the fuel of choice for many developing countries that have the largest expected percentage increase in consumption, and who have limited financial resources to buy cleaner petroleum and natural gas. In the next couple of decades, the environmental consequences of fossil fuel consumption will undoubtedly be a major source of contention among various industrial and developing countries.

As we are depleting our valuable fossil fuel resources, we must find solutions to our increasing energy needs, which must take one or more of these three forms: to stop or even reverse the population growth, to conserve energy and reduce consumption, or to find new energy supplies, mainly in the form of renewable resources. How the future looks will largely depend on how we act to achieve these goals today.


(1) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2009

Further Reading

Meadows, D. H., et al., The Limit to Growth, Universe Books, 1972. Also see, The Limit to Growth: The 30-Year Update, Chelsea Green Publishing Company, 2004.

Diamond, J., Collapse: How Societies Choose to Fail or Succeed, Penguin Group, USA, 2004.

Cleveland, C. J., Encyclopedia of Energy, Elsevier Direct Science, 2004.

The International Journal of Energy, Science Direct Elsevier Publishing Company.

Applied Energy, Elsevier Publishing Company.

Journal of Energy Resource Technology, ASME International.

The Energy Journal, The quarterly journal of the IAEE’s Energy Education Foundation, (

External Links

Energy Citation Database, US Department of Energy (

Environmental Protection Agency (

US Department of Energy (

The NIST Reference on Constants, Units, and Uncertainty (

The Club of Rome (

The Sierra Club (