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 Biomass is energy derived from living matter, and it is another source of renewable energy that starts with the sun. Sunlight fuels photosynthesis, which is the basis for the rest of the food web. However, biomass is different from most renewable energy sources in that it involves the combustion of fuel. It is considered renewable because it uses fuels like plant matter, animal waste, and algae, which regenerate relatively quickly. Biomass can supply both electrical power (known as biopower) and motor vehicle fuel (known as biofuel). It is the largest source of renewable energy in the US, comprising 53% of the country’s renewable energy consumption.
Pros: Although combustion of biomass releases greenhouse gases, some these would be released anyway during decomposition or will be reabsorbed in subsequent regrowth. As a result, many of the emissions cancel out. Biomass resources are not in danger of running out as long as they are managed sustainably. Many sources of biomass already exist and others can be obtained without much expense, so fuel costs are fairly low. Also, biomass plants involve technology that already exists at a reasonable cost. This makes biomass relatively inexpensive overall, especially compared to other renewables. A large amount of biomass in the form of waste wood and crop residue is readily available. Biomass is a reliable resource. It allows more power to be generated when demand is higher and less to be generated when demand is lower. Biomass can directly replace fossil fuels in many power plants and cars.
Cons: Expanding the market for woody biomass creates a financial incentive for cutting whole trees, which gravely threatens forest ecosystems. The extraction and combustion of whole trees can result in more immediate emissions than burning fossil fuels. When grown instead of food crops, biofuels diminish food supplies, leading to increased food prices worldwide. The process of growing some of the most common biofuel crops is highly inefficient. The energy input, usually in the form of fossil fuels, often exceeds the energy output of the final product. Some biomass plants release particulate matter that can cause respiratory disease and other health effects in surrounding communities. These facilities are often too small to be regulated by the Clean Air Act. Cellulosic and algal biofuels can be grown sustainably without interrupting food production, but these newer technologies are not yet practical on a large commercial scale.
Click here to learn how biomass affects forests
Other sources of information on biomass: National Renewable Energy Laboratory - Biomass Energy Basics Southern Alliance for Clean Energy - Learn About Biopower Southern Alliance for Clean Energy - Learn About Biofuels Union of Concerned Scientists - How Biomass Energy Works Resource Maps: National Renewable Energy Laboratory - Biomass Maps 
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