Biomass refers to any an organic material from plants and animals that contains energy. It is considered a renewable source of energy because most products can be obtained within a reasonable time frame. Examples of biomass materials include wood, agricultural crops, waste materials, food, and animal manure. These materials can be burned directly in a power plant or can be converted into liquid biofuels (ethanol, for example, is often obtained from corn).
Despite biomass’ classification as renewable, it is actually one of the dirtiest sources of power, as the process of burning biomass releases the stored carbon. The process of regrowing plants may mitigate this impact, but if biomass production involves unsustainably cutting down forests, the net carbon level rises. For this reason, the organization Greenpeace published a paper against the use of biomass.
Biomass made up just over 1.5% of the US power generation in 2016. Part of the reason for low adoption in electricity generation has to do with biomass’ noncompetitive price. It costs more money to produce a unit of electricity (1 kWh) from biomass than it does to use coal, natural gas, or onshore wind or solar. A list of the price of electricity from different sources can be found here.