Construction/Demolition: Energy, Water, Waste, Emissions

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“The U.S. generates 136 million tons of
construction- and demolition-related wastes every
day. Demolition debris alone can contribute to up
to 40% of the country’s waste.”

“When a buildings’ energy and water requirements
are added in, it becomes clear that their
environmental impact is huge. Buildings swallow
up to 30-40% of the world’s energy and 16% of the
planet’s water requirement …”
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Environmental Science & Technology
<http://pubs.acs.org/subscribe/journals/esthag-w/2008/may/science/rc_buildings.html>

May 21, 2008
Built to demolish, demolish to build

All things must come to the end of their lives,
and buildings are no exception. When buildings
die, they end up in heaps of rubble that make
their way into landfills. Only some parts-the
metals and some of the concrete-get recycled.
Consequently, dead and demolished buildings can
contribute up to 40% of a country’s waste
materials.

A study in ES&T: (DOI 10.1021/es071345l) takes a
life-cycle approach to show that taking into
account the end-of-life impacts of buildings can
increase the recycling of materials from
demolished ones, and thereby significantly lower
a building’s environmental footprint, including
its greenhouse gas emissions.

The U.S. generates 136 million tons of
construction- and demolition-related wastes every
day. Demolition debris alone can contribute to up
to 40% of the country’s waste.

When a buildings’ energy and water requirements
are added in, it becomes clear that their
environmental impact is huge. Buildings swallow
up to 30-40% of the world’s energy and 16% of the
planet’s water requirement, according to the
coauthors of the study, Arpad Horvath and Pedro
Vieira, both environmental engineers at the
University of California Berkeley.

An increasing awareness of buildings’
contributions to global warming has led engineers
and construction companies to perform life-cycle
assessments (LCAs), which analyze a product’s
environmental impact through its life span. The
results of the LCA allow engineers to find ways
to cut energy costs, associated greenhouse gas
emissions, and toxic waste products. There are no
policies that mandate LCAs, but the green
building movement, including the rush to obtain
Leadership in Energy and Environmental Design
(LEED) certification-the nationally accepted
benchmark for green building design,
construction, and operation-has encouraged
designers and builders to pay heed to such
issues. But the end-of-life impacts (such as the
energy used in demolishing a building and
transporting the waste products), the
environmental costs of managing the toxic waste
in the debris, and the benefits of reusing the
waste for new buildings are never considered in
the LCAs that are currently conducted.

Horvath and Vieira developed a hybrid LCA method
that calculates the benefits from the reuse of
building materials. The method, which combines
process-based analysis with economic input-output
data, is not new. What is new is how the authors
used it to solve some of the long-existing
problems associated with assessing future costs
of tearing down buildings (the main problem being
the uncertainty of future impacts and their
costs). Finding data on emissions associated with
building waste and deciding “a priori what’s
going to be important and what is not” is very
difficult because the events will happen so far
into the future, says Horvath.

Instead of predicting the costs of emissions
associated with future demolition of buildings,
the authors credit the use of recycled materials
to the new building being designed. The method
doesn’t directly calculate the end-of-life costs
of the new building, but it helps reduce the
environmental impacts from demolition by
encouraging the reuse of materials.

Using concrete as an example, the researchers
show that ramping up concrete recycling from the
current 27% to even 50% would reduce 2.7-5.6
million tons of CO2 annually, which equals taking
612,000 cars off U.S. roads.

“When building or designing a building, one never
conceives of [the demolition phase], mostly
because it is 40 or 100 years away,” says Robert
Boughton, senior engineer at the California
Department of Toxic Substances Control, a state
agency that regulates toxic wastes. Horvath
agrees. “Few people look so many decades ahead
and try to figure out what is going to happen to
that building. They’re happy to have a shiny new
building and . . . happy occupants.”

The study will provide great value to designers
by making them aware of “overall life cycles” of
buildings, says Boughton. “It’s the first paper .
. . I have seen that really got into this
end-of-life [assessment] and tried to give a tool
and some methodology for doing it.”

It is very “timely” and a good “first stab at the
end-of-life issues of buildings,” adds Aurora
Sharrard, research manager with the Green
Building Alliance, a group of professional
designers and builders. But she cautions that
many challenges remain, including taking into
account building materials that cannot be readily
recycled, such as gypsum. “There is certainly a
lot further to go from here,” she adds. -RHITU
CHATTERJEE

A new report shows a rising trend in the number
of eco-friendly buildings in the U.S.
October 31, 2007

First carbon-neutral building
October 24, 2007

Copyright © 2008 American Chemical Society

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