The National Academies: What You Need To Know About Energy

The National Academies

What You Need To Know About Energy

Jon Sullivan—PDphoto.org

Biomass

Of all the renewable energy sources, biomass (biological matter that can be used as fuel or for industrial production) contributes the most to the U.S. energy supply. In 2008, 7% of our energy came from renewable sources, and nearly 4% of that was from biomass.

Experts predict the contribution from biomass will likely increase more than 55% by 2030.

Wood, the most common form of biomass, has been used by people for thousands of years to cook food and to keep warm. Grasses, agricultural crops (such as corn and sugar cane), landfill waste, and manure are other examples of biomass. Used for a variety of purposes, biomass provides energy to produce electricity, heat, chemicals, and transportation fuels (biofuels). It makes small contributions to each of the economic sectors, but the majority of this energy source goes to industry.

Burning biomass releases about the same amount of carbon dioxide (CO2) as burning fossil fuels. However, biomass is more sustainable than fossil fuels because the CO2 it releases is balanced by the CO2 absorbed by plants growing for the next harvest. Any fossil energy that is used to grow, harvest, and process fuel from biomass releases some of that net CO2, but overall, biomass contributes significantly less to climate change than fossil fuels. In fact, if a biomass power plant were equipped to capture and sequester the CO2 it generates, as has been proposed for coal-fired power plants, it could be a net absorber of CO2.

Despite this hopeful picture, it is important to take into account the effect of converting intact ecosystems (such as forests, peatlands, savannas, or grasslands) to grain or fuel crop production. The resulting release of biomass and soil carbon to the atmosphere in the form of CO2 may greatly exceed the greenhouse-gas savings associated with biofuel production on such lands for many years. This phenomenon is referred to as a “carbon debt.”

Experts predict the contribution from biomass will likely increase more than 55% by 2030. Much more research needs to be done on its use as an energy resource, but there is promise that it will reduce our nation's dependence on fossil fuels, decreasing the emission of greenhouse gases and lessening our reliance on foreign sources for our energy supply.

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Energy Hands-on

What do you know about energy?

According to the Corporate Average Fuel Economy (CAFE) standards updated in December 2007, what is the average miles per gallon (mpg) required for new cars, SUVs, and light trucks (combined) by 2020?

  • Sorry, that’s incorrect.

    Based upon the 2007 CAFE standards, the new average mpg required by 2020 is 35 mpg.

  • Correct!

    Based upon the 2007 CAFE standards, the new average mpg required by 2020 is 35 mpg.

  • Sorry, that’s incorrect.

    Based upon the 2007 CAFE standards, the new average mpg required by 2020 is 35 mpg.

Energy Defined

Greenhouse Gas

A gas which, like a greenhouse window, allows sunlight to enter and then prevents heat from escaping—in this case, from Earth’s atmosphere. The most common greenhouse gases are water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), halocarbons, and ozone (O3).

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