[GSBN] embodied energy and sequestration

Fri May 7 12:19:57 UTC 2010

Dear all

Maybe there is confusion here between cement and lime

Lime can absorb C02 during carbonation and this can make a small  
contribution to carbon sequestration over its life in a building

Cement however does not in most cases as cement works best if it does  
not carbonate unlike lime.

The argument that C02 is stored in concrete is a  bogus argument put  
about by the cement and concrete industry to try and greenwash cement.
The carbonation argument seems to be based on the idea that concrete  
can be crushed at the end of life and that this has some carbonation  
benefit
See
http://www.sustainableconcrete.org.uk/main.asp?page=85

The C02 is emitted during the manufacture of cement and is not  
recovered in my opinion . It contributes to fossil fuel energy wastage  
and global warming
Even the use of recycled material like ash involves energy though the  
cement industry have made great strides in reducing this

Cement manufacture remains one of the highest emitters of C02 in all  
human activity as alternatives are not being used in many parts of the  
world

Pragmattically we probably all use a bit of cement from time to time  
but it should be avoided if there are better alternatives like lime or  
earth
Here is an interesting paper which discusses these issues and compares  
cement to alternatives

http://www.springerlink.com/content/56266t21424h4854/

Calculation of sequestration  in wood straw etc.

A paper on this is being prepared by David Robson of University of  
Cumbria and initial findings have been presented to the UK Renewable  
Building Group
Several GSBN UK members are part of this group

This research will be made available when complete and will hopefully  
provide some hard data on the sequestration contribution of renewable  
bio based materials

Tom

On 7 May 2010, at 04:13, Mészáros Attila wrote:

> Dear All,
>
> I completely agree with Derek. Though the amount of the reabsorbed CO2
> could be nearly 50 % of the portland cement's dry mass, the CO2  
> emission
> during the production is higher than this amount.
> The net CO2 production of portland cement production and curing is
> positive. The whole process does not sink, but produces CO2. It is  
> pure
> chemistry and physics.
>
> So I am really surprised on Martin's info on IPCC's perception.
> I know personaly the hungarian member of IPCC, Diana Ürge-Vorsatz, she
> is also a physisist.
> So if we can have a bit more info, we can act. First informal ways,  
> and
> then even formaly...
>
> Attila
>
> Attila Mészáros
> CEO, CereDom Ltd
> email: meszaros.attila at ceredom.hu
> tel: +36 20 9772258
>
> 2010.05.06. 23:22 keltezéssel, Derek Roff írta:
>> Thanks, Martin. Could you clarify a bit about this sentence? Do the
>> sources that you quoted give an explanation?
>>
>> "cement-based products in contrary are accepted to reduce the PCF
>> (product-carbon-footprint) as the CO2 used for production is stored
>> for a long time."
>>
>> What I find confusing, is that production of cement produces a lot of
>> CO2 from fossil fuels in mining, processing, calcining, and  
>> utilizing.
>> It produces/releases a fair amount of sequestered CO2 from the
>> limestone during the calcining chemical reaction. I'm not thinking of
>> any point at which "the CO2 used for production" is stored at all. A
>> small amount of CO2 is reabsorbed from the air by finished concrete,
>> but what I have read is that this is a tiny fraction, and needs to be
>> tiny, to maintain the integrity of the concrete.
>>
>> So what CO2 storage are they talking about?
>>
>> Derek
>>
>> --On Thursday, May 6, 2010 9:24 PM +0200 martin oehlmann
>> <moehlmann at wanadoo.fr> wrote:
>>
>>> Dear all,
>>>
>>> however not much response here on this issue... some possible
>>> interesting observations in the meantime:
>>>
>>> According the perception of IPCC and UN-FCC straw and wood are not
>>> seen as CO2-sink, yet CO2 neutral, cause of the durability is
>>> “difficult” to calculate. In contrary cement-based products in
>>> contrary are accepted to reduce the PCF (product-carbon-footprint)  
>>> as
>>> the CO2 used for production is stored for a long time. (source:
>>> Memorandum Product Carbon Footprint, German Ministry for  
>>> Environment,
>>> Nature Protection etc.)
>>>
>>> Comment: compliments for the cement lobby, low cost cementbased
>>> massproduction for housing with a lifespan 30-40 years.
>>>
>>> If planted forests get cut after 30 years and seen as a CO2 sink, a
>>> high quality building which lasts 100 years and longer built with
>>> natural materials better should be perceived as storage, if the
>>> intention from IPCC and UN-FCC is to support sustainable
>>> constructions.
>>>
>>> Nice day and all the very best,
>>>
>>> Martin Oehlmann
>>>
>>> Brittany
>>
>>
>>
>> Derek Roff
>> Language Learning Center
>> Ortega Hall 129, MSC03-2100
>> University of New Mexico
>> Albuquerque, NM 87131-0001
>> 505/277-7368, fax 505/277-3885
>> Internet: derek at unm.edu
>>
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>
>
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Tom Woolley

Rachel Bevan Architects
80 Church Road
Crossgar
Downpatrick
BT30 9HR
tom.woolley at btconnect.com
028 44 830988

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