[Cob] suspicious embodied energy figures for lime

[Shannon Dealy]

On Fri, 7 Sep 2007, Ron Becker wrote:

[snip]
> Portland Cement 94 lb sack 381,624 BTU
> Lime, hydrated 100 lb sack 440,619 BTU
> Common brick 1 block 13,570 BTU
> Concrete block 1 block 29,018 BTU
> Earth (Adobe) block (mechanized production) 1 block (10X4X14) 2,500 BTU"
[snip]

The portland cement/lime numbers are relatively meaningless for comparison 
purposes, you need to examine the BTU's relative to a constant unit of 
functionality you can achieve from the material such as making uniform 
sized blocks in a common mixture, or area you could cover with a plaster 
made using it as an ingredient, etc.  Beyond that, your comparison needs 
to take into account environmental damage over the life of the material 
(C02 emissions in manufacture, waste at end of life, etc.) as well as 
required functionality.  While you can make a plaster from lime or cement, 
your ratios with other ingredients will likely be different, as will the 
appropriateness of using lime or cement for a given application.  Cement 
will tend to be stronger, less breatheable, and more brittle than lime in 
a given application, and depending on what you are doing these 
characteristics could be either good or bad.  I'm no fan of cement, but 
your decision to use any given material needs to properly weigh all the 
tradeoffs.  Except for cob of course which is perfect for all applications 
and therefore should be used for everything (I had some for lunch earlier 
today ;-)

FWIW.

Shannon C. Dealy      |               DeaTech Research Inc.
dealy at deatech.com     |          - Custom Software Development -
                       |    Embedded Systems, Real-time, Device Drivers
Phone: (800) 467-5820 | Networking, Scientific & Engineering Applications
    or: (541) 929-4089 |                  www.deatech.com