Sustainably Harvested Wood Helps Reduce Our Carbon Footprint
Among its many environmental benefits, wood has a positive role to play in the fight
against climate change. Wood is energy and waste efficient, and offers greater potential
for re-use than other materials. Sustainable forestry and the use of wood products
help reduce carbon dioxide in the atmosphere, one of the main causes of climate
change.
Climate Change
Sustainable forestry and the use of wood products each have a positive role to play
in reducing carbon dioxide in the atmosphere, which is generated when fossil fuels
such as coal and oil are burned for energy. Carbon dioxide traps heat that would
otherwise radiate into space and is a major cause of global warming.
Wood is thought by many to be the only major building material with a negative carbon
footprint. Through photosynthesis, forests absorb carbon dioxide and store it in
their trees and soil. Absorption is the greatest when trees are young and growing
vigorously, and tapers off as they mature. Once they die and start to decay, their
stored carbon dioxide is released back into the environment. If trees are harvested
sustainably and manufactured into building products, the carbon dioxide is stored
in the products while the forest regenerates with young trees that absorb even more
carbon dioxide. This achieves a net reduction in emissions.
In Canada, frequent low-intensity wildfires have played an important role in the
health of most forests and ecosystems, burning smaller trees and undergrowth and
leaving large trees mostly intact. But, as human populations have increased and
cities have expanded, wildfires have been suppressed to protect human life, property
and the economic value of the forest. As a result, Canada’s forests have grown
collectively older than they would have naturally, which means they could be releasing
more carbon dioxide than they absorb on an annual net basis. To find out, the federal
government is developing a National
Forest Carbon Monitoring, Accounting and Reporting System. Older forests
are more susceptible to insect infestations and often have forest fuel conditions
that represent a risk for catastrophic fires, which burn hotter than normal wildfires
with devastating results. Both of these natural disturbances trigger huge releases
of carbon dioxide.
The good news is that certain forest management practices, such as frequent tending
and fertilization, help the forest grow more quickly and absorb more carbon dioxide.
Active management, which involves thinning the forest, removing dead trees and clearing
debris, can reduce the intensity of wildfires and help to protect against the spread
of insects and disease.
If forests are managed sustainably for maximum absorption of carbon dioxide, wood
products complete the cycle by storing the carbon dioxide for decades, if not centuries,
with the added benefit of reducing fossil fuel consumption. Studies have shown that
wood products require less energy to extract, process, transport, construct and
maintain over time when compared with steel or concrete, and that wood’s superior
insulating properties help to reduce the amount of energy needed for heating and
cooling in most climates.
Sources
Athena Sustainable Materials Institute www.athenasmi.ca
Canadian Forest Service: http://cfs.nrcan.gc.ca/
Canadian Wood Council: www.cwc.ca
Consortium for Research on Renewable Industrial Materials: www.corrim.org
Forest Products Association of Canada: www.fpac.ca/
National Council for Air and Stream Improvement: www.ncasi.org/
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Wood and Greenhouse Gas Emissions
Life cycle assessment studies show that wood has less global warming potential than
materials such as steel and concrete when considered over its life. But the forest
industry is seeking a more complete picture of its carbon footprint. Working with
the National Council for Air and Stream Improvement
(NCASI), the Forest Products Association of Canada
(FPAC) has undertaken a project to assess the greenhouse gas emissions that occur
throughout the industry’s value chain, including direct and indirect emissions,
such as those associated with electricity use, as well as the impact of efforts
to reduce emissions, for example by using renewable energy or recycling. The information
will be used on an ongoing basis to assess and compare the implications of different
climate change mitigation strategies.
Sources
Athena Sustainable Materials Institute
www.athenasmi.ca
Natural Resources Canada
cfs.nrcan.gc.ca/forestresearch/subjects/climate
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Energy Efficiency
Energy efficiency is one of the central goals of green building. As much as one
third of the energy produced in North America is used to heat, cool and operate
buildings, much of it in the form of non-renewable fossil fuels such as oil and
natural gas. Burning fossil fuels releases large amounts of greenhouse gases –
so the issue of climate change has made reduction a priority. Benefits also include
reduced costs.
Wood helps to minimize energy consumption in several ways. In terms of embodied
energy, which includes the energy required to extract, process, manufacture, transport,
construct and maintain a material or product, life cycle assessment studies show
that wood significantly outperforms steel and concrete.
One study, conducted by the Consortium for Research on Renewable Industrial Materials
(CORRIM), compared the environmental impact of homes framed with wood and steel
in Minneapolis and wood and concrete in Atlanta – the framing types most common
to each city. According to the report, the homes framed in steel and concrete would
require 17 and 16 per cent more embodied energy from extraction through maintenance
than their wood-framed counterparts.
Wood also has better insulating properties – 400 times better than steel and
15 times better than concrete. Wood’s cellular structure contains air pockets,
which limit its ability to conduct heat and help to minimize the energy needed for
heating and cooling. Concrete and steel are solid throughout and, as a result, facilitate
heat loss in many climates and increase energy consumption.
Sources
Athena Sustainable Materials Institute
www.athenasmi.ca
Consortium for Research on Renewable Industrial Materials
www.corrim.org
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Wood and Waste
Wood buildings provide decades or even centuries of service. However, most buildings
in North America are replaced within 50 years, usually as a result of changing needs
rather than structural problems. This makes wood an excellent choice because it
has less environmental impact than other materials, it can be reused or recycled,
and a structure made with wood can be easily adapted for alternate uses.
Life cycle assessment shows that wood’s environmental impact is so low that
it could be replaced several times before it matches the environmental impact of
materials such as steel and concrete.
Comparative studies show there is virtually no waste produced during the manufacture
of wood products. Chips, sawdust and construction residue are manufactured into
high-value composite materials, such as medium-density fibreboard and finger-jointed
lumber, or burned for energy, replacing fossil fuels.
When wood products are used responsibly, it is also easy to reduce the amount that
goes to landfill. This includes efficient planning to reduce waste from building
projects, proper maintenance to make siding, windows and other products last longer,
and a greater focus on reuse and recycling.
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Recycled Content
Building products should be assessed on their complete environmental profile, not
a single attribute like recycled content.
Although recycling makes sense intuitively, it is not always the best environmental
solution. For example, it takes a tremendous amount of energy to recycle used carpet
into new carpet. Carpets that achieve a high rate of recycled content also use more
polyvinyl chloride (PVC) – which is considered by many to be the worst plastic
from an environmental health perspective.
Most of the time, construction materials with significant recycled content were
in fact downcycled, which means the new product is a lower-grade. For example, concrete
becomes aggregate and some wood products are turned into landscaping material or
mulch.
While downcycling does reduce landfill waste, products that are reused offer higher
value. This is why more building professionals are designing structures that can
be deconstructed, making it easier to separate components within the building so
they can be reused.
A recent study found that wood currently offers the best opportunities for reuse.
Most concrete cannot be reused, other than some pre-cast structural components.
Reusing steel reduces transportation costs and about half of the energy required
to refine steel from ore. Salvaged wood, on the other hand, requires very little
additional energy to process, is low in embodied energy and stores significant amounts
of carbon dioxide.
Engineered wood products that bond together smaller pieces of wood fibre offer a
high-performance, consistent, reliable and environmentally responsible choice for
any project, large or small, residential or commercial.
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