Sustainable energy sources are those that can easily be replenished or renewed. Among the most sustainable are energy harnessed from the sun, wind, water and the earth’s internal heat. Biomass energy sources, such as wood, waste and crops, are also considered sustainable because trees and crops can always be planted. While unsustainable energy sources like coal have been used as a source of fuel for centuries, until the mid-1800s, wood supplied almost 90 percent of the nation’s energy needs.

Unsustainable Energy Sources

Unlike sustainable energy sources, petroleum, coal and natural gas are exhaustible. There is a limited amount of fossil fuel energy sources in the world. Replacing exhaustible sources of energy with renewable sources is a question of when, not if.

Sustainable Energy Use

In 2010, around eight percent of all energy consumed in the United States came from sustainable sources, according to the US Energy Information Administration (EIA). Over 50 percent of sustainable energy goes towards generating electricity. Biomass is primarily used to heat homes, to generate steam for industrial use and to create biofuels like biodeisel and ethanol. Biomass fuels account for around four percent of the nation’s energy use.

The implementation of renewable energy has increased as prices for natural gas and oil rise. Government investment and incentive programs have helped increase the use of sustainable energy as well. Concern over the harmful effects of gas emissions from the burning of fossil fuels has also driven the growth of the renewable energy sector.

The Future of Sustainable Energy

While the use of sustainable energy sources is expected to continue to grow, the EIA projects that exhaustible sources will still be in demand for many years to come. Unlike exhaustible energy sources, renewable energy does not emit harmful gases into the atmosphere. By decreasing the demand for fossil fuels, sustainable energy use extends the supply of exhaustible energy sources as well.