Biomass is regarded as a renewable energy source and is more environmentally friendly compared to the production and burning of other non-renewable fuels (coal, gas, and oil). Biomass systems and the processes they use do produce and release some CO2 into the atmosphere when combusted, however, it is no more than the amount absorbed by plants during their lifetime. This is why biomass fuel and biomass pellets are regarded as being low carbon, and even more so if it is used is from sustainable and local sources.