It’s no secret that the cement industry has a dirty past, emitting nearly 5% of global CO2 emissions. Why is that? Because traditionally, in order to make cement you heat up limestone in a kiln which is powered by fossil fuels (primarily coal) and when you heat up limestone, it off- gases a lot of CO2. But that isn’t the whole story, what people might not realize is that after cement is manufactured, it naturally sequesters CO2 from the atmosphere in a process called “carbonation”. Since no two batches of cement are 100% identical, carbonation rates vary considerably with concrete properties, which also change depending on where in the world the materials originated. Yet on a global average, roughly a third of cement’s process emissions are re-absorbed within the first two years, and over the course of decades, this number rises to 48%. But the cement industry won’t settle for reduced carbon emission they want net-zero. In the past ten years Jeffery Rissman’s research, CarbonCure Technologies Inc., and DeCristofaro chief technologies officer of Solidia Technologies have collectively made huge advancements in carbon sequestrating, making the cement industry a solution instead of a problem in the fight against climate change.
Jeffrey Rissman is the Industry Program Director and Head of Modeling at Energy Innovation. He leads modeling efforts for the firm’s Energy Policy Solutions to determine the policies that most effectively help meet climate and energy goals. In a Green Biz article, Rissman highlights some of the policies that could incentivize the cement industry to reach a carbon-negative future. One of the suggested policies was carbon pricing, such as a carbon tax that gives cement makers a financial incentive to install carbon capturing equipment and make other innovative upgrades to their facilities. Along that same vein, Rissman proposes government research and development support that drives down the cost of new technologies, new biofuels and techniques for electrical generation of the high temperatures used to heat the kiln in the cement-making process. Lastly, one of the most important things the cement industry lacks is industrial process emissions standards and energy efficiency standards. Holding the industry accountable for the emissions they emit will drive the industry to grow in new ways and ultimately make it more profitable.
Although most of us would like industrial emitters to stop producing CO2 all together, the reality is that it will probably be a long time before we see an emission free industrial revolution. We can also be certain that this process will not happen overnight. So the question is how to we deal with this situation in the mean time? CarbonCure is a company leading a global movement to reduce the carbon footprint of the built environment, using recycled CO2 to improve the manufacturing process of the world’s most abundant man-made material, concrete. CarbonCure uses CO2 sourced from industrial emitters as an ingredient in the concrete mixing process, creating a more sustainable masonry product with a lower carbon footprint. As mentioned above, concrete already sequesters CO2 naturally, but by adding it into the mix before it even has a chance to cure greatly increases the amount of CO2 it traps. Furthermore, the patented CarbonCure Technology is retrofitted into existing concrete plants in a single day, making the transition to a lower carbon footprint seamless for the industry.
How is it done?
A computer takes care of executing the proportions of CO2 to cement ratio, insuring that each batch is consistent and has the optimal properties for making a sustainable product. Once the CO2 is injected into the wet concrete mix, the CO2 reacts with the calcium ions from the limestone in the cement mixture. As this process is happening the CO2 is chemically changing to calcium carbonate which becomes permanently embedded in the concrete. Since the CO2 was chemically changed into a mineral, this ensures that the CO2 will never be released back into the atmosphere. Moving forward, companies like CarbonCure should be an example of how an ancient process can be improved for modern times.
Much like CarbonCure, Solidia Technologies wanted to reduce the carbon footprint of the cement industry, and achieved that through a different approach. Solidia Technologies came up with a new recipe for cement that uses less limestone, and more clay lowering the amount of heat needed (less fossil fuels) to process the materials and amount of CO2 initially off-gassed. Solidia Technologies new cement also needs to sequester carbon in order to cure, greatly increasing the amount of carbon it captures throughout its lifecycle.
The Bigger Picture
Accountability, innovation, and drive to make a more sustainable future is the current path of the cement industry. People build with concrete because it typically last two to three times longer than other common building materials, its versatile (can be used for foundations, walls, floors etc.), and has a greater thermal mass, meaning it is more energy efficient because of its ability to absorb and retain heat. For all of these reasons, concrete is one of the world’s most used building materials. This material is here to stay, but the process and recipe is evolving to make the future of our built environment, as well as our natural one, a better place to live in.
Written by Allison Devlin