# Unit 5: Energy

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Energy for lighting, heating and cooling our buildings, manufacturing products, and powering our transportation systems comes from a variety of natural sources. Nonrenewable energy is finite and cannot be replenished within a human timescale. Examples include nuclear energy and fossil fuels. In contrast renewable resources are replenished on shorter time scales, and it is thus possible to use them indefinitely. All energy sources have and some environmental and health cost, and the distribution of energy is not equally distributed among all nations.

Modified by Melissa Ha and Rachel Schleiger from Challenges and Impacts of Energy Use from Environmental Biology by Matthew R. Fisher (licensed under CC-BY)

• 16: Fossil Fuels
Fossil fuels are nonrenewable sources of energy that formed from ancient organisms. They include coal, oil, and natural gas. Coal is mined and then burned to produce heat to generate electricity. Oil and natural gas can be extracted through conventional wells or through unconventional methods, such as fracking. Fossil fuel use harms human health as well as the environment.
• 17: Nuclear Energy
Nuclear energy relies on radioactive isotopes, which are unstable. Nuclear reactions release heat, which can be harnessed into electricity. The use of nuclear energy is does not release greenhouse gases or significantly contribute to climate change. However, nuclear accidents, while rare, have severe and long-lasting impacts.
• 18: Renewable Energy
Renewable energy sources are replenished on short time scales and can thus be used indefinitely. Examples of renewable energy include wind, solar, geothermal, hydropower, and biofuels. The use of renewable energy, along with energy conservation, limits the environmental impact of energy use.

Thumbnail image - "Renewable energy on the grid" is in the Public Domain

This page titled Unit 5: Energy is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Melissa Ha and Rachel Schleiger (ASCCC Open Educational Resources Initiative) .