Renewable and nonrenewable resources

Nature provides numerous energy resources. Nonrenewable resources were the primary source of energy for the twentieth century. However, with the depletion of nonrenewables, interest in renewable forms of energy has generated increasing research and development of renewables.

Background

Nonrenewable resources cannot be readily replaced after consumption. A is one that is continuously available, such as solar energy, or one that can be replaced within several decades, such as wood.

Nonrenewable Energy Sources

Nonrenewable resources may be subdivided into four categories: metals (such as copper and aluminum), industrial minerals (such as lime and soda ash), construction materials (sand and gravel), and energy resources (coal, oil, and uranium). Of the nonfuel substances, metals are most prone to depletion by overproduction, but recycling can prolong their useful lifetime almost indefinitely.

Construction materials, although not readily recyclable, are abundant and ubiquitous in the Earth’s crust, rendering them a virtually unlimited resource. Although less plentiful, the most widely used industrial minerals are unlikely to be depleted in the near future; on the scale of centuries, however, they are an endangered resource if current levels of production are maintained. It is probable that environmental concerns will reduce future production.

The major forms of nonrenewable energy production are fossil fuel combustion (using oil and coal) and nuclear fission (using uranium). According to the World Factbook, of the total energy consumed by Americans in 2022, about 21 percent was from renewable resources, 60 percent was from fossil fuels, predominantly oil, and 18 percent was nuclear.

Coal was the first to be used extensively, and it remained the most abundant in the beginning of the twenty-first century. Coal can be burned directly or converted into or petroleum products, through the expenditure of additional energy. When used as fuel, coal creates many problems. Mines are environmentally destructive, and coal is the most difficult fossil fuel to transport. When coal is burned, vast quantities of sulfur compounds (which form sulfuric acid in the atmosphere) are released, while the carbon in the coal becomes carbon dioxide, a greenhouse gas believed to contribute to global warming. The carbon in coal also has many other valuable (nonpolluting) uses in the chemical industry.

Oil is the world’s major source of energy because it is abundant and relatively inexpensive; however, its high rate of use will result in its depletion during the twenty-first century. When burned as gasoline in cars, it releases carbon dioxide; various dangerous air pollutants, such as carbon monoxide and nitrogen oxides; and uncombusted (a major cause of photochemical smog). Natural gas, formed when organic materials decompose, is usually found with petroleum reservoirs. Its supply, rate of consumption, and probable future are comparable to those of petroleum. It is widely used because it is relatively inexpensive, clean, and nonpolluting (although it does add carbon to the atmosphere).

Tar sands, principally found in Canada, are a low-grade source of petroleum that is feasible to mine and process only when oil prices are relatively high. Two additional problems limit this source: About as much energy is required to extract usable oil as is created when it is combusted, and the process has raised environmental concerns. Oil shales, abundant in the western United States, appear theoretically to be a major source of future petroleum products. The amount of oil tied up in shale exceeds the remaining total world reserve of oil. To extract oil, however, the shale must be mined and heated by processes requiring large quantities of water in regions where water is scarce. Additionally, the total energy required for extraction exceeds the energy created when the oil is burned.

Nuclear reactors produce energy through controlled fission of uranium 235. No air pollution is produced, the mining operations are relatively small and safe, and the resource being consumed has no other known use. On the other hand, reactor technology is sophisticated and elaborate, and complicated devices are prone to breakdowns. A reactor breakdown can have disastrous consequences if radioactive materials are released into the environment. Of equal or greater concern is how the by-products of nuclear power production—nuclear waste—should be disposed of over the long term.

Renewable Energy Sources

The most abundant renewable energy resource is solar energy, the source of most other renewables as well as the original source of fossil fuels. The supply is enormous and inexhaustible, but most is wasted because it occurs in a dilute form that requires expensive hardware to concentrate. Also, it reaches Earth in its most dilute form during the winter, when it is most needed for heating. In cloudy regions it is not even available when demand for it is greatest.

Like solar energy, wind represents a large and potentially inexhaustible source of energy. However, when wind energy is used to generate electricity, expensive collectors are required. Wind energy is not feasible everywhere, and even when feasible, it is not always available. In 2022, wind energy totaled 10.1 percent of the total energy production in the US, and hydropower, power derived from moving water such as that provided by hydroelectric dams, totaled 5.8 percent. Many of the best sites have already been dammed, however, and development of a number of other sites is unwise because of ecological reasons or the sites’ scenic beauty.

Tidal energy utilizes the ebb and flow of tides to create electricity by trapping seawater at the extremes of high and low tide and releasing it through turbines. Although a potentially large energy source, it is economically feasible only where there are naturally high tides (4.5 meters or more) and where a narrow inlet encloses a large bay.

Geothermal energy uses the heat from natural hot springs to create steam to power turbines, which are used to create electricity. Because the heat must be close to the surface, there are few known sites from which electrical energy can be extracted economically. Also, because pipelines must be run over many hectares to collect steam, the power-generating stations tend to be ugly and noisy.

Vegetation (biomass) energy uses plants or animal products derived from plants as a source of fuel. This source includes wood, organic wastes, ethanol, and methane gas from biodigestion. This type of renewable resource is renewable only if harvesting is controlled and if resources exist to cultivate the source. Thus, trees must be given sufficient time to mature, and corn must be cultivated before ethanol can be produced. Although vegetation has a long history as a source of fuel, efficient and sustainable techniques had yet to be introduced in 2022, when biomass represented only 1.5 percent of the total energy production in the US.

Bibliography

Boyle, Godfrey, ed. Renewable Energy. 2d ed. Oxford University Press, 2004, oro.open.ac.uk/3044/. Accessed 1 Jan. 2025.

Cassedy, Edward S., and Peter Z. Grossman. Introduction to Energy: Resources, Technology, and Society. 3rd ed., Cambridge University Press, 2017.

Evans, Robert L. Fueling Our Future: An Introduction to Sustainable Energy. Cambridge University Press, 2007.

Gelles, David, et al. "The Clean Air Future Is Arriving Faster Than You Think." The New York Times, 17 Aug. 2023, www.nytimes.com/interactive/2023/08/12/climate/clean-energy-us-fossil-fuels.html. Accessed 6 Jan. 2024.

González, Pablo Rafael. Running Out: How Global Shortages Change the Economic Paradigm. 2nd ed., Algora, 2008.

Greiner, Alfred, and Willi Semmler. The Global Environment, Natural Resources, and Economic Growth. Oxford University Press, 2008.

Kozlowski, Ryszard, Gennady Zaikov, and Frank Pudel, eds. Renewable Resources: Obtaining, Processing, and Applying. Nova Science, 2009.

Kruger, Paul. Alternative Energy Resources: The Quest for Sustainable Energy. John Wiley & Sons, 2006.

Pimentel, David, ed. Biofuels, Solar, and Wind as Renewable Energy Systems: Benefits and Risks. Springer, 2010.

Twidell, John, and Tony Weir. Renewable Energy Resources. Routledge, 3rd ed., Taylor & Francis, 2015, doi.org/10.4324/9781315766416. Accessed 6 Jan. 2024.