Four years after the changeout of 1,200 uncertified wood
stoves in Libby, Montana, the definitive air quality study has been
released. Not surprisingly, it found
that changing out stoves improved air quality and children’s health. But some findings were surprising. For one, indoor air quality did not always improve;
in fact, it got worse in some homes. Another interesting find was that
no health differences could be found in kids from homes with wood stoves compared
to those without them. Overall, the air
quality benefits were not as great as expected. The detailed report was published along with a thorough critique of the report by health experts pointing toward what
future studies should also consider.
* Air emission standards in the United
States typically regulate the specific type of device, the fuels, and heat outputs.
A recent report indicated that this may allow gaps and variation in coverage,
and some residential and small-to-medium–sized biomass units may not be subject
to environmental regulations (Handley et al. 2009). In contrast, regulations in
Europe are issued according to heat output and type of feeding device (manual
or automatic), which provides 100% coverage. More importantly, European PM2.5 standards for
wood-burning appliances are significantly lower at about 0.02 to 0.05
lb/million BTU heat output compared with state regulations in the United States
at, for example, 0.1 lb/million BTU in Massachusetts and 0.6 lb/million BTU in
New York State (Handley et al. 2009). This indicates that in the United States
there is room for improvement in terms of reducing emissions from wood-burning
appliances. (p. 40)
* It is not clear whether the total number
of wood stoves in the community increased in the meantime, because more people
may have chosen wood as a cheaper fuel, because of an increasing population
size, or both. (p.43)
* In addition, there may be other sources of
PM2.5
in
the area, such as wood- or coal-burning fireplaces and boilers that were not
covered by the changeout program. New York State has noted a tripling in the
sales of outdoor wood boilers since the early 1990s (p. 44)
* The wood stove changeout program should be
considered a success because 95% of older, high-polluting wood stoves in Libby,
Montana, were replaced with more efficient certified wood stoves or with
heating systems that did not burn wood. .. However, the air quality improvement
was not as large as might have been expected based on the dominant contribution
of wood burning to ambient PM2.5 concentrations in the area and the approximately
50% expected reduction in emissions anticipated from each certified stove
compared with uncertified models. (p. 45)
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