The greenhouse gas, carbon dioxide, has been present in our atmosphere for thousands of years. Although plants consume CO2, the supply is excessive. To label some sources as natural and some as man-made is futile. Here we discuss how producing cement aggravates carbon dioxide levels.
To Illustrate
Much of mankind spends considerable time in temperatures around the 80 to 100 degree range. If that temperature increased by 30 to 40 degrees, health and welfare would be endangered.
Some carbon dioxide is necessary for proper ecosystem function. But as carbon dioxide increases, the planet’s welfare is called into question. So what represents the percentage carbon dioxide due to cement production?
Limestone to Lime
There are many materials containing a limestone (calcium carbonate, CaCO3). While this ingredient is used in producing cement, it is first changed into lime (CaO). The reaction is
CaCO3 + Heat → CaO + CO2↑
Yes, with heat one molecule of lime is produced. But one molecule of carbon dioxide gas also results. How much lime and carbon dioxide? The molecular weight of lime is 56.1. The molecular weight of carbon dioxide is 44.0. So for every 2,000 lbs. of lime, 1,569 pounds of carbon dioxide results also. That is huge! This source alone aggravates carbon dioxide levels. But we mentioned two sources. What is the other one?
Heating the Limestone
The heat mentioned in the above equation is no small amount of heat. It amounts to about 1,000 degrees Celsius (1,832 degrees Fahrenheit). This takes lots of fuel. That fuel is the second source of carbon dioxide.
Cement Production Aggravates Carbon Dioxide Levels
This is so significant. Cement is used to make concrete. The carbon dioxide from concrete production amounts to 5 percent of the total CO2 worldwide. If that sounds small, remember the temperature illustration above. Taking CO2 “off the top” is considered important by researchers and the cement industry. They actively seek ways to reduce that contribution.
Note: You might also enjoy Surprising Insights on Global Warming by Meteorologist Jon Plotkin
References:
- Columbia University – Earth Institute: State of the Planet: Emissions from the Cement Industry
- U.S. Geological Survey Minerals Yearbook 2001: Lime, by M. Michael Miller
- The Shelly Company: How is concrete made from limestone?
- The Smithsonian – December 2011: Green Cement, by Michael Rosenwald
