Every manufacturing industry should assess its impact on the environment, and the portland cement and concrete production industries are no exception. Environmental self-scrutiny may yield ways to mitigate the industries' impact on the environment.
A variety of factors influence climate on both a long- and short-term basis. The factor of which we have the most knowledge is carbon dioxide (CO2), a so-called greenhouse gas. It tends to block radiation from the earth's atmosphere and therefore tends to produce a warming effect.
The cement industry produces four major emissions that have a cooling or heating effect on the earth through an effect on radiative forcing—the change in net irradiance in watts per square meter (Wm-2). In contrast to dust, sulfur, and oxides of nitrogen (NOx) emissions, CO2 emissions from the global cement industry are significant, and they are increasing. The contribution of the global cement industry to worldwide man-made CO2 production is about 8.3%.
Cement production currently increases by about 3% per year, and it is likely that the contribution of the cement industry to CO2 emissions is likely to keep pace with or overtake global population increases. To reduce human-led global warming and climate change, eventually CO2 emissions must decline to a very small fraction of current emissions.
We cannot get around this fact: conversion of limestone into clinker requires the evolution of CO2. However, there are alternatives to today's greenhouse gas-producing cement. A second major step to decreasing the total amount of CO2 produced by the global cement industry would be to decrease the proportion of cement in concrete. A third step toward decreasing the total amount of CO2 produced by the global cement industry would be to decrease the number of buildings using cement.