Biomass refers to the organic material that is used for production of energy. This energy production process is referred to as Bioenergy. Biomass is primarily found in the form of living or recently living plants and biological wastes from industrial and home use. Burning plant-derived biomass releases CO2, but it has still been classified as a renewable energy source in the EU and UN legal frameworks because photosynthesis cycles the CO2 back into new crops. In some cases, this recycling of CO2 from plants to atmosphere and back into plants can even be CO2 negative, as a relatively large portion of the CO2 is moved to the soil during each cycle. Cofiring with biomass has increased in coal power plants, because it makes it possible to release less CO2 without the cost associated with building new infrastructure. Co-firing is not without issues however, often an upgrade of the biomass is most beneficial. Upgrading to higher grade fuels can be achieved by different methods, broadly classified as thermal, chemical, or biochemical Biomass is organic material that comes from plants and animals, and it is a renewable source of energy. Biomass contains stored energy from the sun. Plants absorb the sun's energy in a process called photosynthesis. When biomass is burned, the chemical energy in biomass is released as heat. Biomass can be burned directly or converted to liquid biofuels or biogas that can be burned as fuels.