The Problem:
Though it is not the first thing to come to mind, concrete production is a problem that has been shown to contribute significantly to the world's overall production of Carbon dioxide that is released into the atmosphere. Concrete is the second most used substance in the world and its production has been found to release 5%- 6% of the overall carbon dioxide emissions. The most common form of cement that is mixed is called portland cement. Portland cement is a mixture of both crushed limestone and aluminosilicate clay that is then cooked in a kiln. The product of heating the calcium carbonate yields a product of both carbon dioxide and the desired calcium oxide.
A Solution:
When the limestone is decarbonized, this creates 60% of the carbon emissions from the total process of creating cement. The best way to mitigate the production of carbon dioxide would be to use alternatives to limestone. A variety of different materials can be used in place of limestone, including volcanic ash, a variety of clays, finely ground limestone, ground bottle glass, and industrial waste products like blast furnace slag which is a byproduct of manufacturing iron and fly ash which is another byproduct from burning coal. By using these, we are able to avoid the majority of carbon production from the process required to make cement.
Implementation:
A certain goal must be set when planning on implementing the use of alternatives when we consider the production of cement on a large scale. An attainable goal would be a 40% total use of alternatives during production. If 40% of all production would turn to the use of alternatives, this would mitigate the overall problem by saving an approximate 440 million tons of carbon emission every year. Over the year 2018, the total use of alternatives was %31 of all cement production. This produced an approximate 4061 million metric tons of carbon dioxide. Two different scenarios are presented where the use of alternatives in the total industry is anywhere from 39% to 54% of the overall production of cement. This range, over a 30 year period could save 8–16 gigatons of carbon dioxide production.
Costs of Implementation:
The overall cost of completing a scenario where 54% of all cement production was switched to alternative methods, would be around $5055 billion as an average cost over a 30 year period like described above. Where the marginal cost between traditional and alternative cement comes out to be around $63.5 billion
Environmental Co-benefits:
Besides reducing carbon emissions, the use of alternative concrete can also reduce waste and the overall consumption of natural products like limestone. Using waste from coal industries and the iron manufacturing industry reduces the total amount of mining that is necessary to be done for acquiring limestone needed to make concrete and reuses materials otherwise labeled as bi-product or waste. Reducing the amount of mining can in turn reduce the overall amount of particulate matter that is released into our atmosphere from these practices. Finally, the recycling of used products like concrete debris and post-consumer glass can also be used to make more cement.
While changing the composition of cement to help lower carbon emissions, places like PCA or the Portland Cement Association are working in other ways to make the process of manufacturing more sustainable. In a company video, they describe how different steps are being taken to use alternative sources of fuel from landfills, and revitalizing depleted limestone mines.
Reference:
“Fly Ash Brick.” Wikipedia, Wikimedia Foundation, 28 Feb. 2021, en.wikipedia.org/wiki/Fly_ash_brick.
“CONCRETE.” Carbon Smart Materials Palette, materialspalette.org/concrete/.
“How Cement Is Made.” How Cement Is Made, www.cement.org/cement-concrete/how-cement-is-made#:~:text=Cement%20is%20manufactured%20through%20a,silica%20sand%2C%20and%20iron%20ore.
Detz, Jo. “Global Warming Has Concrete Problem When It Comes to CO2.” EcoRI News, EcoRI News, 25 Oct. 2019, www.ecori.org/climate-change/2019/10/4/global-warming-has-a-co2ncrete-problem.
Hawkin, Paul. “Alternative Cement.” Project Drawdown, Penguin Books, 12 Feb. 2020, www.drawdown.org/solutions/alternative-cement/technical-summary.
