Coal is a very efficient fuel, in that it provides more energy per kilogram than biomass, but it is not a renewable one. Coal is mined from carbon sinks that took millions of years to form, so when it is burned to produce energy it increases the total amount of CO2 and other potent GHGs in the atmosphere.
Energy made from woody biomass comes from burning carbon drawn out of the atmosphere by trees within the last 150 years; much of the carbon from those trees is being held in long-lived forest products and in most jurisdictions in Canada, harvested areas are reforested and newly-planted trees start drawing in CO2 from the atmosphere within a year of harvesting. Those factors make woody biomass a renewable energy source and an important alternative in the transition away from fossil fuels (Figure 1).
