Biomass is one of the oldest sources of energy for humans: since 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 generate renewable electricity.
Biomass is organic plant or animal matter that can generate energy. This includes many everyday items – crops, trees, garbage, algae, animal manure, and human waste.
Biomass can be converted into several 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. To learn more about using biomass as a heating source for your home or business, visit our clean heating and cooling section.
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 recycles them back into carbon dioxide and water and releases the energy the plants initially 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 balance out these emissions, some consider it a carbon-neutral resource (though this is heavily debated among many scientists and environmentalists.)
Three primary ways to generate electricity from biomass are burning, converting biomass to fuel, and via bacterial decomposition.
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.
Another way to generate biopower from biomass is by converting it to a gaseous fuel. Placing biomass in a high-temperature environment without oxygen 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 of making bio-oil is similar to generating syngas, but with one key difference: in both scenarios, the biomass needs to be in an environment altogether 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.
Biopower can also be generated from organic waste material thanks to bacterial decomposition. This process collects human and animal waste 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.
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.