How Biopower Works

To many people, the most familiar forms of renewable energy are the wind and the sun. But biomass (plant material and animal waste) is the oldest source of renewable energy, used since our ancestors learned the secret of fire.

• Note: This page addresses biopower—using biomass to generate electricity. For more information on biofuels, go to the UCS Clean Vehicles Program’s biofuels pages.

Biomass is a renewable energy source not only because the energy in it comes from the sun, but also because biomass can re-grow over a relatively short period of time compared with the hundreds of millions of years that it took for fossil fuels to form. Through the process of photosynthesis, chlorophyll in plants captures the sun's energy by converting carbon dioxide from the air and water from the ground into carbohydrates—complex compounds composed of carbon, hydrogen, and oxygen. When these carbohydrates are burned, they turn back into carbon dioxide and water and release the energy they captured from the sun.

Several recent studies show little to no economic potential to increase biopower in the U.S. over the next two decades because of its relatively high costs compared with other renewable energy and low carbon technologies (EIA 2015, EPA 2015, NREL 2015, UCS 2014, UCS 2015). Other studies of nearly decarbonizing the power sector by mid-century show that more efficient, advanced biopower technologies using low-carbon feedstocks, such as agricultural residues and energy crops, could provide a modest contribution of up to 15 percent of U.S. electricity generation (NREL 2012, UCS 2013).

But like all our energy sources, biopower has environmental risks that need to be mitigated. If not managed and monitored carefully, biomass for energy can be harvested at unsustainable rates, damage ecosystems, produce harmful air pollution, consume large amounts of water, and produce net global warming emissions.

Assessing the potential role of biopower as a climate solution requires a look at its lifecycle carbon emissions­­­­—which vary according to the type of feedstock, the manner in which it is developed and harvested, the scale at which it is used and the technology used to convert biomass into electricity. The lifecycle carbon emissions of biopower should also be compared to the fossil fuels it’s displacing and other zero and low carbon solutions it’s competing with.

NOTE: We are currently in the process of updating the content on this page to reflect the latest research and understanding of key biomass issues. Check back soon for updates.