Biomass energy is defined as energy derived from renewable organic materials such as wood products, agriculture residue, fish waste, waste water plant sludge, etc. In Southeast Alaska we most commonly think of biomass as wood products such as cordwood, wood pellets, and wood chips.
From an energy perspective, biomass is simply solar energy, stored as a solid chemical fuel. Through the process of photosynthesis, plants absorb CO2 out of the atmosphere and store that carbon in the structure of the plant. Harvesting trees and burning them releases the energy stored in those carbon structures.
Heating with biomass can be very cost effective compared to heating with oil or electric resistance. For example, a wood pellet stove can provide heat for approximately two-thirds the cost of providing that heat with oil or electric resistance at current Juneau prices. Modern biomass heating systems are efficient, clean, economical, and convenient.
In terms of CO2 emissions, biomass energy is 'carbon neutral.' Whenever any carbon-based fuel is combusted, CO2 is a resulting byproduct. It doesn't matter if it's wood or natural gas, oil, or coal. The difference between wood and fossil fuels is that the carbon contained in trees was extracted in the atmosphere, and will return to the atmosphere when the tree dies and decays, or is burned. The forest and the atmosphere are in equilibrium - burning biomass energy takes advantage of that natural cycle, and as long as new trees are allowed to grow up to replace the trees that are harvested, the system is carbon neutral. Burning fossil fuels such as oil introduce 'new' carbon to the atmosphere, thus increasing the overall concentration of CO2. Harvesting and transporting wood requires the use of some fossil fuels, so it is probably more accurate to state that biomass is 'carbon advantaged' compared to any of the fossil fuel alternatives.