Renewable energy  |  Biomass

Biomass 101: what you need to know

Last updated 12/24/2019

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Biomass is one of the oldest sources of energy for humans: since times of early humans, we’ve been using biomass in various forms to cook our food, heat dwellings, and more. In addition to providing heat, biomass can be used for generating renewable electricity.

What is biomass?

Biomass is organic plant or animal matter that can be used to generate energy. This includes many everyday items – agricultural crops, trees, garbage, algae, animal manure, and human waste. 

Biomass can be converted into several different types of energy: it can be burned directly for heat or converted into gases or liquids for burning and/or electricity generation. Electricity generated from biomass is sometimes also referred to as biopower or bioenergy. We’ll dive into the basics of using biomass for renewable electricity below – if you’re interested in learning more about using biomass as a heating source for your home or business, visit our clean heating and cooling section.

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How does biomass work?

Biomass is considered a renewable energy source because supply does not run out. As opposed to fossil fuels that take millions of years to form, biomass grows and re-grows relatively quickly through the photosynthetic process.

Photosynthesis converts carbon dioxide and water into carbohydrates that feed and grow plants. When we burn biomass, these carbohydrates undergo a reaction that converts them back into carbon dioxide and water and releases the energy that the plants originally captured from the sun.

Importantly, and unlike most other types of renewable electricity, burning biomass releases carbon dioxide–a greenhouse gas–into the atmosphere. However, because living plants capture carbon and help to balance out these emissions, some consider it to be a carbon-neutral resource (though this is heavily debated among many scientists and environmentalists.)

There are three primary ways to generate electricity from biomass: burning, converting biomass to fuel, and via bacterial decomposition.

how biomass works

Burning

Converting biomass into electricity works similarly to generating electricity from coal: during this process, biomass is burned in a boiler to produce steam. The steam then flows over turbine blades, which rotate and power a generator that creates electricity.

Biomass fuels

Another way to generate biopower from biomass is by converting it to a gaseous fuel. When you place biomass in a high-temperature environment without the presence of oxygen, it produces a synthesis gas, also known as syngas. This gas can then be burned in a boiler or a gas turbine for electricity generation.

You can also produce biopower by converting biomass into liquid fuel, or bio-oil. The process to make bio-oil is similar to generating syngas, but with one key difference: in both scenarios, the biomass needs to be in an environment completely void of oxygen, but to produce bio-oil, the biomass is heated at lower temperatures than required for the gaseous state. Similar to diesel and other types of oil, bio-oil can be utilized in furnaces or turbines to generate electricity.

Bacterial decomposition

Biopower can also be generated from organic waste material thanks to bacterial decomposition. In this process, human and animal waste is collected in oxygen-free anaerobic digesters. Waste decomposes in the digesters and releases methane and other gases, creating what is known as biogas. Biogases are then filtered and burned to produce electricity.

The role of biomass power today

According to the Energy Information Administration (EIA), biomass only accounted for 2 percent of U.S. electricity generation in 2018. It is a less prevalent source of electricity in the U.S. than other types of renewable energy like hydropower (7 percent in 2018) and wind (7 percent in 2018). In 2018, biomass accounted for roughly the same amount of U.S. electricity as solar, though the use of solar is expected to grow further as costs continue to decline.

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