Wood burning is a significant source of climate pollutants and contributes to global warming.
Living trees absorb carbon dioxide (CO2) from the air as part of the photosynthetic process and store the carbon as cellulose and other carbon-containing carbohydrates.
When wood is burned, the CO2 that was absorbed over years while the tree was alive is released back into the atmosphere all at once.
Adding more CO2 when we need less
For the same amount of energy, burning wood emits more CO2 than coal. As air quality expert Dr. Gary Fuller explains, there is “more carbon in the air immediately after burning wood for electricity compared with fossil fuels, and more carbon in the air after an evening in front of the wood fire than using the central heating.”
Short-lived climate pollutants
But CO2 isn’t the only problem. Short-lived climate pollutants (also called short-lived climate forcers or super pollutants) are responsible for almost half of global warming, and lowering their emissions is critical.
Focusing only on cutting CO2 emissions is not enough to prevent rising global temperatures from crossing tipping points that will cause irreversible impacts. We need to do both.
Since short-lived climate pollutants only last a short time in the atmosphere—days to decades, compared to centuries for CO2—lowering their emissions will slow warming faster than any other strategy.
The terms black carbon and elemental carbon both refer to a similar type of carbon particle. The difference in terms reflects the different methods used to measure and describe them.
Black carbon is the most strongly light-absorbing component of particulate matter. A ton of black carbon in the atmosphere has the equivalent warming potential of 900 tons of CO2 (PDF) In the atmosphere, it warms clouds and affects the size and distribution of cloud droplets, which in turn can affect rain patterns and alter the amount of solar energy that is reflected back into space.
Once black carbon particles have fallen back to earth, they absorb the sun’s energy on the ground. If they land in areas covered with snow or ice, the resulting darkening of the snow’s surface and the absorption of the sun’s solar radiation promotes melting. This is an especially serious problem in Arctic nations, but can affect all snow-bound places.
Wood burning is a significant source of black carbon
Wood burning is a significant source of black carbon emissions. For example, the California Air Resources Board has projected that by 2030 residential wood burning will be the state’s largest anthropogenic source of black carbon emissions.
Researchers in Finland noted in a study, “Like in many other countries, residential wood combustion is the largest single source of black carbon and many other short-lived climate forcers.” They concluded that wood heating is “the least climate-friendly option to heat a house.”
A study in Switzerland found that, at the sites that were measured, wood burning contributed up to 33% of black carbon emissions. It was noted that, “This is a noticeable high fraction as the contribution of wood burning to the total final energy consumption is in Switzerland less than 4%.”
Domestic heating, “mainly wood burning,” contributes more than 50% of Europe’s black carbon emissions.
In 2020, all of Canada’s electric generation, including from coal, was responsible for 0.7% of Canada’s black carbon emissions, while residential wood burning was responsible for 23%. Canada’s oil and gas industry, by comparison, contributed 8.6% of Canada’s black carbon emissions, while vehicles on Canada’s roads and highways contributed 21%.
Organic carbon and brown carbon
When wood is burned, it also produces organic carbon, which is a complex mixture of compounds. Research has shown that some organic carbon particles are highly absorbing in the near-UV spectrum, and that this affects the global climate balance.
For example, a study in coastal California provided evidence that the light-absorbing properties of organic carbon “in atmospheres burdened with residential wood smoke” are secondary to those of black carbon, “but not insignificant.”
These near-UV-absorbing particles are also known as brown carbon.
A study conducted in France found that brown carbon emissions from residential wood burning were significant. The researchers concluded that stronger regulation of residential wood burning would not only improve air quality, but have climate benefits as well.
A study in the United Kingdom looked at atmospheric nitrated phenols from residential wood burning. The researchers determined that although nitrated phenols may make up a small portion of the total organic aromatics measured in the air, they are nonetheless a potentially important contributor to light absorption in the near-UV spectrum by brown carbon from wood burning. “They can thus affect atmospheric radiative transfer and photochemistry and with that climate and air quality.”
Methane emissions from wood burning
According to the Intergovernmental Panel on Climate Change (IPCC), methane will cause 88 times as much global warming in the first 20 years after emission as the same amount of CO2 and 34 times as much over 100 years.
Researchers have pointed out that wood burning is a source of methane.Environment, biomass and climate references