Greenhouse Gas Effects of Burning Wood

Perfect Combustion

• Ideally, wood should not contribute to greenhouse gases at all. When wood is perfectly combusted, it turns directly into carbon dioxide, water and heat. The water is released back into the atmosphere along with the carbon dioxide, while the heat is used to provide warmth, generate electricity or produce steam. Although carbon dioxide is a greenhouse gas, it can be absorbed by new trees that replace the ones cut for firewood. These new trees can then be burned, starting the cycle over again with no net gain in carbon dioxide.

Actual Combustion

• Unfortunately, wood does not burn perfectly. When wood is burned, only some of it is converted into carbon dioxide. Some of the wood is converted into carbon monoxide, methane, nitric oxide or other compounds and some is released into the air as particles of ash. When the wood is smoldering, it burns far less efficiently than during its first phase of burning--and wood fires tend to smolder longer than they burn outright. Methane, carbon monoxide and other trace gases are potent greenhouse gases, warming the atmosphere much more quickly than carbon dioxide does. These factors increase the effect of wood on global warming.

Waste Wood

• Many companies in the wood industry use waste wood to generate steam and electricity to power their plants. If these companies were not using the waste wood, they would have to transport the wood to either a recycling center or a landfill, creating greenhouse gases through vehicle emissions. Many of these companies otherwise would use electric power provided by power companies burning fossil fuels, which increase greenhouse emissions.

Clear-Cutting

• Although the greenhouse gases released by burned trees are in theory trapped by new trees, in practice this is not always the case. When areas of forest are cut down and turned into housing, farms, grazing land and other uses, the wood in those forests is never replaced. If that wood is burned, its carbon is released into the atmosphere but there is no subsequent generation of trees to absorb it. This causes a net gain in greenhouse gases in the atmosphere.

Renewable Resources

• Wood is a renewable resource like hydroelectric, solar and wind energy. When fossil fuels are burned, they release carbon into the atmosphere but that carbon is not absorbed again by a new generation of fossil fuels. Wood does not have this problem. However, because it often does not burn cleanly and releases both greenhouse gases and substances such as ash that are bad for human health, wood is an inferior fuel to wind, water and sun, which do not release emissions into the atmosphere.