Biomass is renewable organic material that comes from plants and animals. Biomass contains stored chemical energy from the sun that is produced by plants through photosynthesis. Biomass can be burned directly for heat or converted to liquid and gaseous fuels through various processes
Biomass was the largest source of total annual U.S. energy consumption until the mid-1800s. In 2022, biomass accounted for nearly 5% of U.S. total primary energy consumption. Biomass is used for heating and electricity generation and as a transportation fuel. Biomass is an important fuel in many countries, especially for cooking and heating in developing countries.
Biomass sources for energy include:
- Wood and wood processing waste—firewood, wood pellets, and wood chips, lumber and furniture mill sawdust and waste, and black liquor from pulp and paper mills
- Agricultural crops and waste materials—corn, soybeans, sugar cane, switchgrass, woody plants, algae, and crop and food processing residues, mostly to produce biofuels
- Biogenic materials in municipal solid waste—paper products; cotton and wool products; and food, yard, and wood wastes
- Animal manure and human sewage for producing biogas (renewable natural gas)
Source: Adapted from The National Energy Education Project (public domain)
Source: U.S. Energy Information Adminstration (public domain)
Biomass can be converted to energy in different ways
Biomass is converted to energy through various processes, including:
- Direct combustion (burning) to produce heat
- Thermochemical conversion to produce solid, gaseous, and liquid fuels
- Chemical conversion to produce liquid fuels
- Biological conversion to produce liquid and gaseous fuels
Direct combustion is the most common method for converting biomass to useful energy. All biomass can be burned directly for heating buildings and water, for providing industrial process heat, and for generating electricity in steam turbines.
Thermochemical conversion of biomass includes pyrolysis and gasification. Both processes are thermal decomposition processes wherein biomass feedstock materials are heated in closed, pressurized vessels called gassifiers at high temperatures. The processes mainly differ in the temperatures and in the amount of oxygen present during conversion.
- Pyrolysis entails heating organic materials to between 800° F and 900° F (400° C and 500° C) in the nearly complete absence of free oxygen. Biomass pyrolysis produces fuels such as charcoal, bio-oil, renewable diesel, methane, and hydrogen.
- Hydrotreating is used to process bio-oil (produced by fast pyrolysis) with hydrogen under elevated temperatures and pressures in the presence of a catalyst to produce renewable diesel, renewable gasoline, and renewable jet fuel.
- Gasification entails heating organic materials to between 1,400° F and 1,700 F (800° C and 900° C) with injections of controlled amounts of free oxygen or steam into the vessel to produce a carbon monoxide- and hydrogen-rich gas called synthesis gas or syngas. Syngas can be used as a fuel for diesel engines, for heating, and for generating electricity in gas turbines. It can also be treated to separate the hydrogen from the gas, and the hydrogen can be burned or used in fuel cells. The syngas can be further processed to produce liquid fuels using the Fischer–Tropsch process.
A chemical conversion process known as transesterification is used for converting vegetable oils, animal fats, and greases into fatty acid methyl esters (FAME) to produce biodiesel.
Biological conversion of biomass includes fermentation to make ethanol and anaerobic digestion to produce biogas. Ethanol is used as a vehicle fuel. Biogas, also called biomethane or renewable natural gas, is produced in anaerobic digesters at sewage treatment plants and at dairy and livestock operations. It also forms in and may be captured from solid waste landfills. Properly treated renewable natural gas has the same uses as fossil fuel natural gas.
Researchers are working on ways to improve these methods and to develop other ways to convert and use more biomass for energy.
Biomass provided about 5% of U.S. energy in 2022
In 2022, biomass accounted for 5% of U.S. energy consumption, or about 4,930 trillion British thermal units (TBtu). The types, amounts, and the percentage shares of total biomass energy consumption in 2022 were:
- Biofuels—2,419 TBtu—49%
- Wood and wood waste—1,984 TBtu—43%
- Municipal solid waste, animal manure, and sewage—411 TBtu—8%
The industrial sector is the largest consumer of biomass for energy in the United States
The amounts—in TBtu—and percentage shares of total U.S. biomass energy use by consuming sector in 2022 were:
- Industrial—2,266 TBtu—46%
- Transportation—1,565 TBtu—32%
- Residential—539 TBtu—11%
- Electric power—413 TBtu—8%
- Commercial—147 TBtu—3%
The industrial sector accounted for the most, in terms of energy content and percentage share, of total annual U.S. biomass consumption in 2022. The wood products and paper industries use biomass in combined heat and power plants for process heat and to generate electricity for their own use.
The transportation sector accounted for the second-highest amount and percentage share of biomass (as biofuels) consumption in 2022.
The residential and commercial sectors use firewood and wood pellets for heating. The commercial sector also consumes, and in some cases, sells renewable natural gas produced at municipal sewage treatment facilities and at waste landfills.
The United States is a net exporter of biomass energy
Densified biomass fuels (wood pellets and other densified biomass fuels) have become a U.S. export commodity in recent years. In 2022, the United States exported about 8.8 million tons of wood fuel pellets (Table 8).
Last updated: June 30, 2023, with data from the Monthly Energy Review, April 2023; data for 2022 are preliminary.