Which of the following is NOT identified as a renewable energy source?

Natural gas is categorized as a fossil fuel rather than a renewable energy source. Fossil fuels are formed from the remains of ancient plants and animals and take millions of years to develop, which means they cannot be replenished on a human timescale once they are depleted.

In contrast, renewable energy sources are those that can be naturally replenished in a relatively short period of time. Windpower utilizes the natural movement of air to generate electricity, biomass refers to organic materials that can be used for fuel, and geothermal power harnesses heat from the Earth's core. These sources are sustainable and can continuously provide energy without the risk of depletion, making them essential in the transition toward sustainable energy solutions.