When the calcium carbonate is calcined it releases CO2.
CaCO3 + heat -> CaO + CO2
So while they have an activated lime that is a good CO2 scavenger for the reaction, this "green" process has its own carbon footprint.
Net CO2 is not impacted at all! So, it comes from eggshells. It does not matter if it is clamshells, eggshells, limestone, or whatever.
"Lime Production:
Like cement production, the industrial lime production results in carbon dioxide emission when limestone is heated up.
As well as straightforward 'quicklime' production, a second type of lime called 'dolomitic' quick lime is also produced using a mixture of limestone and magnesium carbonate.
Quicklime production is thought to result in about 800kg of carbon dioxide per tonne, while dolomitic quicklime produces slightly more at about 900kg per tonne."
Like cement production, the industrial lime production results in carbon dioxide emission when limestone is heated up......... Quicklime production is thought to result in about 800kg of carbon dioxide per tonne, while dolomitic quicklime produces slightly more at about 900kg per tonne.
Maybe the "man made" global warming skeptics need to look at this. (if they haven't already)
The "manmade" advocates place all the "CO2" attention on fossil fuels and they claim their models demonstrate the "fossil-fuel-caused" additions account for atmospheric increases of CO2. I wonder?
According to the US geological survey, quicklime production in the US alone, for the century from 1904 to 2004:
(http://minerals.usgs.gov/ds/2005/140/lime.pdf)
amounted to 1,010,400,000 metric tons,
which at 800kg of CO2 per ton
and 1,000kg in a ton,
it amounts to a C02 contribution from US quicklime production of 808 million, 320 thousand tons (US alone).
I don't know how that compares to "fossil fuels". Maybe a new breed of "man made" GW advocates will make a case to finding an alternative to quicklime instead of an alternative to gasoline. LOL