Biomass is the mass of living organisms such as plants, animals, and microbes, as well as cellulose, lignin, carbohydrates, lipids, and proteins from a biochemical standpoint.
Greenhouse gas is any gas that absorbs infrared radiation (net heat energy) released from the Earth's surface and reradiates it back to the Earth's surface, thus contributing to the greenhouse effect.
The most significant greenhouse gases are carbon dioxide, methane, and water vapor.
When fossil fuels or biomass are burned, carbon dioxide (CO2), a greenhouse gas, is released.
However, the plants that provide biomass for energy capture almost the same amount of CO2 through photosynthesis as is emitted when biomass is burned, making biomass a carbon-neutral energy source.