Most people, when they think about global warming, and the
sources of carbon dioxide in the atmosphere, which, by the way,
just hit 392 ppm last month, think about coal-fired power
plants, or cars and trucks rolling down the highway. Few, if
any, think about the highway itself, or the concrete bridges and
overpasses that negotiate the many roads and rivers that it
encounters along the way. And yet concrete, which is used widely
in highways, buildings, sewers and many other structures, is
responsible for more than 5% of all carbon dioxide pollution.
Not only do our major construction projects employ an awful lot
of this material, but the production of cement, which is the key
ingredient in concrete, produces an exceptionally large amount
of CO2 for every pound of cement. Cement production creates CO2
emissions in two ways: - The process requires extremely high
temperatures and therefore consumes a large amount of fossil
fuel for firing - The conversion of limestone through a process
called calcination releases