Steel and cement
are used for
building highways
and buildings,
while steel is also
used for automobiles
and appliances.
Industrial processes,
such as making
steel and cement,
produce large
quantities of CO2.
The steel industry
accounts for 7%
of worldwide
CO2 emissions,
while producing
cement accounts
for 5%.
Coal is used in
steel industry
blast furnaces.
Limestone is the primary
component of cement.
Limestone and other
clay-like materials are
heated in a kiln at 1400°C
and then ground to form
a lumpy, solid substance
called clinker.
Clinker is combined
with gypsum
to form cement
Heating limestone releases
CO2 directly, while burning
fossil fuels to heat the kiln
also results in CO2 emissions.
Roughly 50% of the
overall CO2 emissions
from making cement
are from the limestone.
So steel is out.
And cement is out.
And since humans
emit CO2-rich air
from their lungs
when they exhale,
( 38,000 ppm versus
415 ppm in the air )
perhaps we need
several billion
fewer people
on this planet too !