This blog contains excerpts from a very important and readable report published
by the World Health Organization (WHO) in 2015. It is primarily from a health and policy perspective and is very valuable for North American as it provides more of a European perspective and is balanced in its approach. The entire 58-page report can be downloaded here.
The report is particularly interesting as it hits on many themes that were considered or included in the 2015 EPA wood heater regulations, some of which will be litigated in 2017. It addresses best available technologies, indoor air quality, efficiency standards, stove changeout programs, black carbon, carbon neutrality, HEPA filters and many other issues. One of the overarching conclusions is that national policy should strongly favor pellet over cord wood appliances, a transition that has already occurred in parts of Europe, but not in the US.
Authors include experts from the US, Austria, Canada, Finland and
Germany. This publication was prepared by the Joint
WHO/United Nations Economic Commission for Europe (UNECE).
The
report describes the health effects of and policy options for dealing with
residential heating with wood and coal in Europe and the United States. The
results presented indicate that it will be difficult to tackle problems with
outdoor air pollution in many parts of the world without addressing this source
sector. National, regional and local administrations, politicians and the
public at large need a better understanding of the role of wood biomass heating
as a major source of harmful outdoor air pollutants (especially fine
particles). This report is intended to help increase such an
understanding.
Executive Summary:
Measures are available to reduce emissions of solid fuels for
residential heating in most places. Encouraging fuel switching (away from coal
and other solid fuels) and use of more efficient heating technologies (such as
certified fireplaces or pellet stoves) can reduce the emissions from
residential wood and coal heating devices. Educational campaigns may also be
useful tools to reduce emissions from residential solid fuel heaters.
Furthermore, filters may reduce health effects from indoor air
pollution. Existing regulatory measures include ecodesign regulations and
labels in the European Union (EU) and technology based emission limits in the
United States of America and Canada. Financial fuel switching and technology
changeout incentives – as well as targeted “no burn” days and ecolabelling –
are other tools available to policy-makers.
p. 2. Residential heating with wood is a sector in which PM2.5
and BC emissions can potentially be reduced with greater cost– effectiveness
than many other emission reduction options. Nevertheless, within Europe and
North America only a few countries or states have set legal limits for minimum
combustion efficiency or maximum emissions of PM and harmful gaseous compounds
like CO and gaseous organic compounds (see section 6).
Coal:
p. 8.
In the USA 55% of homes used coal/coke for space heating in 1940, but this fell
to 12% in 1960, below 5% in the early 1970s and below 1% from the early 1980s
(Schipper et al., 1985; United States Census Bureau, 2011).
One study
estimates that reductions in the use of bituminous coal for heating in the USA
from 1945–1960 decreased winter all-age mortality by 1% and winter infant
mortality by 3%, saving nearly 2000 lives per winter month, including 310
infant lives (Barreca et al., 2014).
Based
on this and evidence that indoor emissions from household combustion of coal
are carcinogenic to humans, the latest WHO indoor air quality guidelines
strongly recommend against the residential use of unprocessed or raw coal,
including for heating (WHO, 2014a).
Infiltration of smoke into homes
p.
10. A household with wood-burning appliances is
likely to be surrounded by other homes with wood-burning appliances, and wood
burning also tends to aggregate temporally; thus, on cold evenings and nights
most homes in the area may be burning wood.
Given that most wood burning occurs in cold locations where
homes are well insulated, buildings are expected to have low infiltration
(meaning that relatively small amounts of outdoor air pollution, including
wood-burning smoke, enter the house and contribute to indoor air pollution),
especially during the heating season.
In North America heating-season outdoor temperature is an
important determinant of infiltration, and infiltration levels are generally
lower in the heating than the non-heating season, when doors and windows are
likely to be open more (Allen et al., 2012). In British Columbia the mean infiltration
fraction of PM2.5 in winter was found to be 0.28, compared to 0.61 in summer,
although infiltration factors for individual homes in winter ranged from 0.1–0.6
(Barn et al., 2008); another study reported similarly low mean infiltration levels
of 0.32 Å}0.17 during the winter (Allen et al., 2009). Combustion of wood in
residential areas and often under cold, calm meteorological conditions can
nonetheless lead to high exposure compared to other pollution sources, owing to
the principle of intake fraction.
Indoor pollution
Modern wood stoves and fireplaces, when operated according to
the manufacturers’ instructions, release some PM and gaseous pollutants
directly into indoor air, although in most cases the evidence for substantial
indoor emissions from these modern stoves is very limited. With poor operation,
poor ventilation or backdrafting, however, elevated concentrations of
combustion products (such as PM, CO, VOCs, NOx and aldehydes) may result
indoors. Acute CO poisoning, which can sometimes even be fatal, may occur due
to indoor wood burning and infiltration of dirty ambient air), especially when
ventilation of the wood-burning appliance is not managed properly.
Stove Change outs
p. 21. Such change-out initiatives have potential limitations. The
Canadian Council of Ministers of the Environment (CCME) – the association of
environment ministers from the federal, provincial and territorial governments
– evaluated 12 stove exchange and educational efforts conducted in Canada and
concluded that exchange programmes may have limitations relating to both the
cost of new technologies and the long service life of appliances once
installed. The assessment supported the use of regulation effectively to curb
the sale of high-emission appliances. This approach is used in a number of
Canadian provinces and American states.
The Canadian National Collaborating Centre for Environmental
Health found that emissions standards (based on best available technologies)
are needed to ensure that the newer devices installed through change-out
programmes are among the cleanest available in the marketplace. Without these
standards, change-out programmes may, in fact, be lost opportunities to install
the cleanest available wood-burning devices, which will be in use for years to
come.
The study also found that removal of conventional noncertified
appliances (through exchanges, time limits or prior to the sale or transfer of
a property) was the most effective strategy included in a model municipal
by-law for mitigation of residential wood smoke (Environment Canada, 2006) (see
“Other regulations and voluntary measures” in section 6). [Click for more on stove change out programs - editor.]
HEPA Filters
While household or individual-level strategies are not typically
part of air quality management programmes, two studies from Canada indicate
that inhome HEPA filtration might reduce health impacts from wood smoke. An
initial single-blind randomized crossover study of 21 homes during winter, in
an area affected by residential wood combustion as well as traffic and
industrial sources, reported a mean 55% (standard deviation = 38%) reduction in
indoor PM levels when HEPA filters were operated (Barn et al., 2008). Use of
the HEPA filters reduced indoor PM2.5 and levoglucosan concentrations by 60%
and 75%, respectively. [Click for more on HEPA filters - editor.]
Regulatory
Emission Limits
p. 26. Over the past decade, the European Commission has worked
towards the possibility of regulating solid fuel local space heaters and
boilers, particularly those that use various forms of woody biomass fuel (wood
logs, pellets and biomass bricks), to create proposed ecodesign emissions
limits.
According to the Commission proposals, implementation of ecodesign
standards would lead to significant reductions of PM2.5 emissions from solid
fuel local space heaters and boilers compared to baseline projections. The
draft regulation for solid fuel local space heaters2 states that in 2030 the
proposed requirements for those products, combined with the effect of the
energy labelling, are expected to save around 41 petajoules (0.9 million tonnes
of oil equivalent (Mtoe)) per year, corresponding to 0.4 million tonnes of CO2.
They are also expected to reduce
PM emissions by 27 kilotonnes per year,
Voluntary Measures
p. 30. The Wood Stove Decathlon, an initiative of the Alliance
for Green Heat, was organized in 2013 to focus creativity and resources on
designing next generation wood stoves. The main goal was to challenge teams of
combustion engineers, engineering students, inventors and stove manufacturers
to build wood stoves that are low-emission, high-efficiency, innovative and
affordable, in a common process that may point to commercially attractive next generation
stove production (Alliance for Green Heat, 2013).
Policy Needs
p. 31 Any renewable energy or climate change related policies
that support combustion of wood for residential heating need to consider the
local and global ambient air pollution impacts and immediately promote the use
of only the lowest emission or best available combustion technologies.
Legal regulations for wood combustion efficiency in new heating
appliances are urgently needed throughout the world. These will both slow down
the current rapid speed of global warming (relating to BC in fine particles and
VOCs that promote ozone formation) and reduce the great burden of disease
caused by wood combustion-derived particles (especially organic compounds
carried by BC). Such regulations should include tight – but technically
achievable – limits in particular for the primary emissions of particulate
mass, gaseous hydrocarbons and CO from new boilers and heaters.
p. 32. As new wood-burning devices become more energy efficient
and emit less pollution (especially PM), national governments need to prepare
heater exchange regulations or voluntary programmes. Municipalities, counties and
states should consider requiring heater exchanges at the time of home remodels
or sales. In many cases, these regulations will be most successful if financial
compensation is offered to assist with the cost of replacing old heaters with those
meeting tight energy efficiency or emission limits regulations.
“No burn” areas are needed. Especially with current combustion
technologies, it is important to define urban areas with dense populations
and/or geographical features (such as valleys between mountains) where
residential heating or cooking with small-scale appliances burning solid fuels
(wood and coal) is not permitted at all or is at least limited to registered
models of low-emission wood combustion devices. Residential heating with coal
in small-scale appliances should also be permanently prohibited, at least in
communities of developed countries, as should the use of wood log burners for
central heating without a sufficiently large water tank (which otherwise leads to
badly incomplete combustion and very large emissions).
Co-benefits for health and
climate
As wood is burned ... carbon is released back to the atmosphere,
not only as CO2 but in most household combustion also in the form of
short-lived greenhouse pollutants such as BC, CO and VOCs including CH4. Thus,
to be perfectly “carbon neutral”, wood fuel has to be not only harvested
renewably but also combusted completely to CO2. For both climate and health
purposes, the form these fuels’ carbon takes when it is released matters
greatly, since BC and CH4 are both strongly climate-warming.
p. 34. A World Bank study found that replacing current wood
stoves and residential boilers used for heating with pellet stoves and boilers
and replacing chunk coal fuel with coal briquettes (mostly in eastern Europe
and China) could provide significant climate benefits.
Another study coordinated by the United Nations Environment
Programme and the World Meteorological Organization found that widespread
dissemination of pellet stoves (in industrialized countries) could improve
health, since these interventions lead to reductions in PM2.5.
If Arctic climate change becomes a focus of targeted mitigation
action (because of threats from rising sea levels, for example), widespread
dissemination of pellet stoves and coal briquettes may warrant deeper
consideration because of their disproportional benefit to mitigating warming
from BC deposition in the Arctic (UNEP & WMO, 2011). The World Bank found
that replacement of wood logs with pellets in European stoves could lead to a 15%
greater cooling in the Arctic (about 0.1 ÅãC). For Arctic nations the modeling strongly
indicates that the most effective
BC reduction measures would target regional heating stoves for
both climate and health benefits (Pearson et al., 2013).
Conclusions
p. 35. Given that residential wood combustion for heating will
continue in many parts of the world because of economic considerations and
availability of other fuels, an urgent need exists to develop and promote the
use of the lowest emission or best available combustion technologies.
It may be preferable in
many cases to focus on making biomass-based home heating more efficient and
less polluting rather than transitioning away from biomass to fossil fuels,
given the climate change implications of using fossil fuel for heating.
