Wood stove changeouts that replace older wood stoves with newer, EPA-certified ones are promoted by the hearth industry as a way to clean the air in wood smoke-impacted communities.
A large and well-documented wood stove changeout took place in Libby, Montana from 2005 – 2008. The hearth industry, US EPA and the state spent over $2.5million to replace most of the wood stoves in the Libby area with EPA-certified ones. They also invested in education programs and proper installation. Most participants in the changeout received a new wood stove, but a small number switched to a cleaner method of heating such as electric or propane.
In the immediate years after the exchange, wood smoke-related particulate matter mass by 28%. However, there was also a general decline in all particulate matter during this time, including from cars and other sources. (On the whole, motor vehicles only made a small contribution to air pollution levels in Libby.)
approximately 80% of Libby’s winter particulate pollution came from residential wood burning. After the changeout, wood stoves still accounted for approximately 81% of Libby’s particulate pollution, although there was a reduction in total PM2.5 mass. Ultimately, after an initial reduction, levels of toxic PAHs remained the same after the changeout as before.
Four years after the end of the exchange, “highly variable” levels of emissions across homes that had received new certified wood stoves. Some houses did not ultimately experience any reduction in PM2.5 at all.
Although some chemical compound amounts were lowered, of elemental carbon did not decrease and levels of seven resin acids increased significantly, including dehydroabietic acid and abietic acid. Airborne potassium levels also rose significantly after the changeout.
“Of the nine wood stoves that have cropped up in my area, the worst by far is the one next door, which belongs to a North Cowichan Wood Stove Exchange recipient. This neighbour’s volume of smoke doubled and I thought he was having a chimney fire, when he relayed to me the good news that he had a brand new stove courtesy of North Cowichan!” In larger quantities, abietic acid is known to in workers who are exposed to pine resin. Dehydroabietic acid has also been shown to be to human epithelial and fibroblast cells and to cause neurological impairments in animal studies.
Residential wood burning remains Libby’s largest source of PM2.5, and, as of mid-2018, Libby is still on the US EPA non-attainment list for particulate standards the Montana Department of Environmental Quality.
In British Columbia, a “did not find a consistent relationship between stove technology upgrades and indoor air quality improvements in homes where stoves were exchanged.” In addition, a 2015 on BC’s wood stove exchange program noted that, in spite of the popularity of the program, “there has not yet been a clear reduction in fine particulate matter pollution coming from residential wood stoves.”
, the wood smoke-impacted city of Launceston, Australia, embarked on a campaign to move citizens away from wood heating. During the 1990s, 66% of households in Launceston heated with wood, and the emissions from these wood heaters accounted for 85% of the community’s wintertime particulate air pollution.
An educational campaign was mounted, and electric heating was promoted as an affordable and non-polluting alternative. Throughout the 1990s, the number of homes that heated with wood declined, as the number that heated with electric rose. From 2001 – 2004, the government ran the Launceston Wood Heater Replacement Program, by the end of which the number of homes heating with wood had dropped from 66% to 30% of all households. Many citizens who had not participated in the program decided to switch to electric on their own without a government subsidy.
Wintertime PM10 concentrations dropped from 43.6μg/m3 before the intervention to 27μg/m3 after. The male death rate was reduced by a “large and significant” amount for all causes, by 11.4%. Wintertime respiratory deaths were reduced by 28% for men and women combined. Similar reductions were not seen in the control city of Hobart.
Ductless air source heat pumps are increasing in availability and affordability, and piped natural gas as the most cost-effective heating in many cities. Newer models can keep a even when outside temperatures reach as low as -20oF (-28oC).
A of the British Columbia wood stove exchange program recommended that air source heat pumps be included as eligible appliances to replace wood stoves in the BC wood stove exchange program. As the report points out, air source heat pumps are included in Washington wood stove exchange programs, “where efforts are focusing on removing wood burning appliances altogether” for the sake of reducing air pollution.
The Bay Area Air Quality Management District in Northern California recently conducted a that did not allow the replacement of wood-burning appliances with more wood-burning appliances. Only cleaner, non-wood forms of heating, including heat pumps, were eligible. The program was so successful, all of the money was spoken for within hours of it being announced. After the changeouts are completed, two thousand polluting wood stoves and fireplaces will have been removed from use in the region.
According to local of the changeout, “air quality officials said the rebates are aimed at reducing public exposure to smoke in winter when cold stagnant air traps pollution near the ground. Tiny soot particles can lodge deep in the lungs and trigger asthma and emphysema attacks, and higher risks of strokes.”
See also: Wood Stoves