Recycling is the Heart of
Steel
The U.S. Steel industry underwent a transformation
in the 1970s, and, today, steel manufacture takes
less energy and is done with one-tenth the manpower
it took 30 years ago.
In 2003, almost 69 million tons of steel were
recycled in the U.S. or were exported for recycling.
About 88 percent of all steel products, and nearly
100 percent of steel used in beams and plates
in construction, are recycled into new steel products
at the end of their useful life.
Courtesy AISC |
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"We have achieved a very efficient production
process and a very high level of recycled content,"
says Christopher Hewitt, a LEED-accredited staff
engineer with the Engineering and Research Dept.
of the Chicago-based American Institute of Steel
Construction, Inc. "What we are saying today,"
Hewitt says, "is that steel is a good choice
for sustainable projects."
An emerging method of analyzing the environmental
efficiency of materials is the use of embedded
energy approaches, sometimes referred to as life-cycle
analysis (LCA). The method involves calculating
the total amount of energy associated with the
production, manufacture, transportation and construction
of materials, their components and by-products.
Unfortunately, LCA is still in its infancy, and
comparisons are difficult, not only in structural
components, but in almost every aspect of construction.
No credible study has yet been done, for instance,
comparing the embodied energy of structural wood
products to steel or concrete in the U.S. construction
market, Hewitt says.
LEED, he says, is moving slowly in the direction
of life-cycle analyses that would award credits
for durability and longevity, but it is unlikely
that that meaningful data from such studies will
be available soon. LEED, however "provides
a snapshot of what is going on in the manufacture
of building materials," Hewitt says, "and
its emphasis on recycling and reuse means that
framing with steel can earn owners ‘green'
credits."
The electric arc furnace (EAF) process, the primary
method in the manufacture of structural beams,
steel plate and reinforcing steel, now uses 95-to-100
percent recycled steel. "Recycling is second-nature
for the steel industry," Hewitt says.
Because it is produced to exact specifications,
on-site waste is negligible. Material from construction
and demolition is easily recycled, and, because
it is dimensionally stable, steel creates a tight
building envelope, leading to better HVAC performance
over time.
"To enhance LEED ratings," Hewitt says,
"it will be important to know the percentage
of recycled steel that is ‘post-industrial'
and the percentage that is ‘post-consumer.'"
That will require data from the mill where the
material is obtained. To access that information,
Hewitt urges users to contact the mill directly
or to visit the AISC website for recycled-content
templates from member mills.
For a more thorough understanding of the recycled
content of steel, Steel Recycling Institute (SRI).
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