Which of the following is NOT a renewable energy source?

• A. Natural Gas
• B. Solar
• C. Wind
• D. Waves and Tides

Answer: (A)

Renewable energy sources come from natural processes that replenish themselves on a human timescale. Solar energy is continuously available from the sun, wind results from atmospheric movement, and waves and tides are driven by ocean dynamics; these sources can be relied on repeatedly as long as the natural processes continue, and they generally produce energy with lower net environmental impact.

Natural gas is a fossil fuel formed from ancient organic matter over geological time and is finite in supply. It doesn’t renew on human timescales, so relying on it as a long-term source is unsustainable. When burned, it releases greenhouse gases, contributing to climate change, which is another reason it isn’t considered renewable.