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Re: GSBN:Cemento (combined responses)



I also think one has to consider that cement is just one material that is used. It is used an awful lot, and this is part of its environmental footprint. However, the reason it is used a lot is that it is made of clay and limestone (available most places in quantity) and results in a very durable and low dollar cost product. I am all for reducing cement use, and changing cement manafucturing to dramatically reduce CO2 and other emissions. however, if the replacement for the apartment buildings in China is, for example, steel, then the CO2 emissions will rise dramatically as steel will use more energy and CO2 for the same beam or column. Lots of cement is used in heavy civil works like roads, and sewers, curbs and sidewalks. There are some replacements, but few work as well.
At the end of the day, I think cement is one of many materials that we need to use more wisely and hence less of, but for many purposes, it is hard to find an equally durable, non-combustible material that has less impact.
One of the clear substitutions is wood framed housing instead of concrete. This works in some places, like where they have trees, but there are limits to height, fire resistance, and durability that are quite practical. For most other applications, like basements,bridges, sewer pipes etc, I think we can gain more by be smarter in its use (optimally designed structures) and dramatically improve is production (e.g. there is little reason why a coal-fired cement plant could not use carbon sequestration.

Graeme North wrote:
Thanks Mark Ð
It looks as though the 6-10% figure so often quoted in green architecture
circles for cement manufacturingÕs CO2 contribution may be partially right-
and wrong.

But see a graph at
<a  target="_blank" href="http://cdiac.esd.ornl.gov/trends/emis/glo.htm";>http://cdiac.esd.ornl.gov/trends/emis/glo.htm</a>

This was in one of the references Mark so kindly put out.  It puts cement
manufacturing contribution at somewhere around  2-3 %  annual global CO2
emissions
So although cement is one of the major players in the world&#xD5;s pollution, and
certainly in the construction industry&#xD5;s contribution, it looks to me that
although its present contribution may now be nearer 2-3 % of overall annual
global CO2 emissions, its cumulative total effect of all human generated CO2
appears to be nearer 8% &#xD0;  does this look right to anybody else?


Graeme,
Graeme North Architects,
49 Matthew Road,
RD1, Warkworth,
New Zealand 0981
Ph/fax +64 (0)9  4259305

www.ecodesign.co.nz





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--
Dr John Straube, P.Eng.
Associate Professor
Dept of Civil Engineering &amp; School of Architecture
University of Waterloo
Waterloo, ON Canada