Cement manufacturing produces 5% of the total greenhouse gases introduced into the atmosphere. It seems like there is a silver lining at the end of the cement journey - concrete.
Photo by thirdblade
Limestone becomes lime or calcium oxide at temperatures of staggering 1000 Celsius in cement production process. This process releases substantial amount of CO2
while the other half of its carbon dioxide releasing is from the usage of fossil fuels to heat them up.
Good thing though, cement seems to cancel out a portion of the amount of detrimental gases after study showed that cement, in its concrete form has the capability to absorb the same gases it has released.
The process of carbonation soaks up CO2
by mortar, concrete and rubbles of demolished buildings; and converts it into other forms of chemicals. There never was concrete evidence on how much CO2
got absorbed in this process.
Zhu Liu of California Institute of Technology in Pasadena and his team set out to do just that. They teamed up with Steve Davis of University of California, Irvine, and other U.S. and European researchers. The group studied the use of cement around the world, the quality and the standard thickness required to complete the building constructions. They also did not leave out the information needed to know about the lifespans of concrete buildings and the cement after the building gets torn down.
Ash Grove Cement Factory in Seattle Washington
The researchers visited construction sites all over China to get the accurate data on different factors and sets of conditions that influence the amount CO2
absorbed by the concrete. The data sets include the size and thickness range of concrete rubbles; and the conditions surrounding them when left out in to open air.
The researchers tested the carbonation and the rate of CO2
absorption in three different conditions and settings - buried, in the open air, and enclosed in a room.
The result showed that between 1930 and 2013, cement has soaked up 4.5 gigatons of carbon or more than 16 gigatons of CO2.
That amount counters the 43% carbon emission in the early stage of cement creation. The researchers reported that amount is more than 20% of the carbon soaked up by forests in recent decades.
Rob Jackson, an earth systems scientist at Stanford University in Palo Alto, California, and chairman of the Global Carbon Project said that findings may not be considered dramatic in the overall amount of carbon emissions, it certainly would add to the list of carbon models and drive strategies to reduce carbon footprint.
The study is published in Nature
See: New Carbon Fix: CO2-Sucking Booster, Synthetic System Faster Than Plants