6.1 - Renewable and Nonrenewable Resources

Learning Objectives

I. Definitions

• Renewable resource: A resource that can be replaced or regenerated naturally. If it is used faster than it regenerates, it is not truly renewable and can be exhausted.
• Examples: sunlight, wind, flowing water (hydroelectric and tidal power), geothermal heat, and biomass like wood or ethanol crops. The CED's key phrase is that renewables are replenished naturally at or near the rate they are used, so they can keep being used again and again.

• Non-renewable resource: An energy source that is depleted by its use and exists in a fixed amount on Earth. It will run out if overused.
• Examples: coal, oil, natural gas, and uranium. Once coal is burned or a uranium atom is split, its stored energy has been transformed into heat and can't be put back, and making new coal or oil takes millions of years.

II. Categories of Renewable Resources

A. Depletable Renewables

• These can run out if overused.

• Examples include biomass like wood. If forests are cut down faster than they regrow, they are not being used sustainably and will run out.

• Charcoal and ethanol (generated from corn) are other examples. Sustainable use requires proper soil care and continuous replanting.

B. Non-Depletable Renewables

• These renewable resources do not run out when overused and cannot be exhausted.

• Examples:
• Sun: Putting up solar panels does not decrease future sunlight.
• Wind: Wind turbines do not lead to less wind in the future.
• Hydroelectric power: Building a dam may have consequences for nearby ecosystems, but the water itself is not destroyed or depleted by its use.

III. Non-Renewable Resources and Consumption Rates

A. Fossil Fuels

• Fossil fuels are the fossilized remains of biomass, compressed under rock layers over millions of years.

• They are non-renewable because humans use them far faster than they regenerate, meaning they do not regenerate on any time scale that matters to us.

• Fossil fuels include coal, oil, and natural gas, and they currently power the vast majority of the world’s energy.

• Based on end-2020 estimates, the world's proven reserves would last about 54 years for oil, about 49 years for natural gas, and about 139 years for coal at the 2020 rate of production (BP Statistical Review of World Energy, 2021). These are rough timelines, not countdowns: they change when new deposits are found or when use goes up or down (see 6.4).

B. Nuclear Power

• Nuclear power is non-renewable because it depends on radioactive elements, primarily uranium.

• Uranium exists in finite amounts on Earth and will eventually run out.

C. The Role of Consumption Rate

• The key factor for whether a source stays renewable is the rate of consumption. Resources have to be consumed at or below the rate at which they regenerate.

• Globally, we are currently deforesting faster than we are reforesting. That pattern of overuse means forests are being depleted and will run out if it continues.