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Re: GSBN:Cemento (% of total C02 emissions)



Thanks very much Mark

I suspect that the source of the 6-10% may partially be speculation that has
travelled by Chinese whispers, but it is included in the
the 1993 paper recently posted which says:
 
CO2 Emissions
 
There are two very different sources of carbon
dioxide emissions during cement production.
Combustion of fossil fuels to operate the rotary
kiln is the largest source: approximately 3/4
tons of CO2 per ton of cement. But the chemical
process of calcining limestone into lime in the cement kiln also produces
CO2:
 
CaCO 3 â CaO + CO 2 limestone â lime + carbon dioxide
 
This chemical process is responsible for roughly
1/2 ton of CO2 per ton of cement, according to
researchers at Oak Ridge National Laboratory.
Combining these two sources, for every ton of
cement produced, 1.25 tons of CO2 is released
into the atmosphere. In the United States, cement
production accounts for approximately 100 million
tons of CO 2 emissions, or just under 2% of our
total human-generated CO 2. Worldwide, cement
production now accounts for more than 1.6 billion
tons of CO2 Ð over 8% of total CO2 emissions from all human activities.

The 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>
shows an increasing contribution from cement manufacturing but a lesser % of
the overall CO2 output.
Your figures show the opposite &#xD0; as you say -  C02 emissions from cement
production not 
only keep increasing, they're a bigger and bigger cut of all C02 emissions.

This latest data seems pretty conclusive &#xD0;
<a  target="_blank" href="http://cdiac.esd.ornl.gov/ftp/ndp030/global.1751_2004.ems";>http://cdiac.esd.ornl.gov/ftp/ndp030/global.1751_2004.ems</a>
- gives 7910 total and 298 for cement in 2004
(the most recent year shown), or about 3.75%.

The 1993 figure from this data is around 2.8% compared to the figure quoted
above of just under 2% so there is some discrepancy it seems  - I assume
that the latest data is more accurate

So a figure of 3.5- 4% for cement&#xD5;s global CO2 contribution seems pretty
realistic to me.

In a way this is of only idle curiosity for me, but the cement manufacturers
are now doing a big push to say how environmentally good their material is,
so its good to have some background data.

And here&#xD5;s an interesting one &#xD0; a local council official here would not let
a neighbour use limestone as a subdivision road base &#xD0; he said that some
figures they had from our weather scientists meant that the acidity in the
atmosphere was expected to increase to such an extent that acid rain
(containing weak carbonic acid) would dissolve the limestone and destroy the
road - 
I have heard that the oceans acidity will increase enough from absorbed
increased atmospheric CO2 over the next 50 years to dissolve the shells of
shell fish and coral &#xD0; I&#xD5;ve not heard of the projection about rain before.

Now if true, where does this leave our huge concrete-based buildings and
infrastructure?


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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