In a recent webinar, Adam Auer, Vice President of Environment and Sustainability at the Cement Association of Canada, and Matt Dalkie, Technical Services Engineer at Lafarge Canada, discussed several new cement and concrete technologies that are helping producers meet the demands of the growing low-carbon concrete trend.
The Global Cement and Concrete Association recently released a Climate Ambition pledge that aspires to carbon neutrality across the industry by 2050. Many cement and concrete companies have already signed this commitment and have had their strategies third-party verified by the Science Based Targets initiative.
“While every company is at a different stage in their carbon neutrality journey, the technology pathway that will help them reach their goals is the same,” said Adam Auer, Vice President, Environment and Sustainability at the Cement Association of Canada. “The bottom line is that getting to net zero cement and concrete will require not just one solution but a whole menu of technologies and strategies.”
3 Key Areas of Focus in Low-Carbon Concrete
There is no silver bullet for the decarbonization of concrete. However, because concrete is made of so many ingredients, there are lots of ways to reduce the carbon impact of the individual components and processes.
Most of the carbon reduction and carbon removal innovation effort is focused on three key areas: low-carbon fuels, low-carbon blended cement, and carbon capture, utilization, and storage technologies.
1. Low-Carbon Fuels
The concrete industry has been focused on fuel efficiency for a number of years for both cost-reduction and carbon-reduction reasons. More recently, the industry began evaluating the move from traditional fuels (e.g. coal) to low-carbon fuels (e.g. renewable natural gas), waste fuels (e.g. non-recyclable plastics, non-recyclable tires, rail ties, etc.), and potentially even carbon-neutral fuels.
According to Matt Dalkie, Technical Services Engineer at Lafarge Canada, these alternative fuels can reduce the carbon emissions of cement manufacturing by up to 40%, depending on how you treat the specific materials from a carbon perspective within the carbon calculation. However, there are some limitations based on the type of technology used for clinker manufacturing and the local availability of such fuels.
2. Low-Carbon Blended Cements
Most producers are already using Portland Limestone Cements (PLCs) and supplementary cementitious materials (SCMs) in their cement or concrete mixes. Further optimizing the use of these materials could reduce cement and concrete emissions greatly.
For example, PLCs use uncalcified limestone in the cement grinding phase of the manufacturing process and can reduce the carbon footprint of concrete by 5-10%. SCMs—which include things like fly ash and slag—can reduce the amount of cement required in a concrete mix, thereby reducing the carbon emissions by up to 30%. Fly ash, for example, is a byproduct of the coal-fired power generation and can replace 30-50% of the cement in a concrete mix, reducing the carbon footprint by 10-20% depending on the replacement level specified. However, with coal-fired power generation winding down globally, the availability of fly ash is becoming increasingly constrained. Slag is a byproduct of the iron manufacturing process and can replace 40-50% of the cement in a mix and up to 90% for some specialty applications. The carbon reduction from slag can be up to 30% depending on the replacement level specified.
It’s important to note that some of these solutions have durability and finishability implications in certain applications and, as a result, are not accepted in all specifications.
3. Carbon Capture, Utilization, and Storage Technologies
Innovation in carbon capture, utilization, and storage (CCUS) technologies is arguably the most exciting development in the concrete industry.
Carbon capture makes it possible to capture up to 100% of the carbon emissions from cement manufacturing. These captured emissions can be stored safely underground, injected back into concrete to strengthen it, or used to make other products like synthetic aggregates or fuels.
Some of the key players in the CCUS space include:
CarbonCure manufactures a retrofit technology that can be installed in any ready mix concrete plant today. It injects carbon dioxide (CO2) into wet concrete in order to improve its strength and performance. These improvements enable concrete producers to realize cost savings through mix optimization while growing their business within the green building market.
Blue Planet’s technology uses CO2 as a raw material for making carbonate rocks. The carbonate rocks can be used in place of natural limestone rock mined from quarries. The company is in the process of building a plant in Pittsburg, California, and recently completed a successful test project at San Francisco Airport.
Solidia is backed by Lafarge and is a cement manufacturing technology that can be produced in traditional cement kilns using less energy. It offers precast concrete manufacturers a way to produce lower carbon construction materials, permanently storing CO2 in concrete pavers and blocks to prevent CO2 emissions from being released into the atmosphere.
Svante is a carbon capture technology that can capture CO2 directly from industrial sources at less than half the capital cost of existing solutions. Svante enables technology like CarbonCure to complete the circle in the circular economy—Svante captures the CO2 from the cement kiln and CarbonCure injects it back into ready mix concrete. CarbonCure demonstrated this circular process a few years ago as part of the Carbon XPRIZE.
Carbon Engineering is a direct air capture (DAC) technology that can capture CO2 directly from the atmosphere.
CarbonCure is a big proponent of all of these technologies because they're all contributing to carbon capture, utility, and storage innovation. When combined with either of the two carbon capture solutions described—even at the prototypical stage—CarbonCure could help producers build a completely circular economy within their plants.
The Role of Specifiers
It goes without saying that specifiers of concrete control many of the levers that affect how much progress the industry can make in low-carbon concrete. By moving toward performance-based specifications, specifiers allow for more innovation in concrete mix design.
“Prescriptive specifications are based on empirical relationships, but they do not permit creativity and innovation,” said Matt. “Performance specifications, on the other hand, define requirements for a particular structural element. They meet the spirit of the design and offer producers flexibility to achieve project goals—like embodied carbon limits—in innovative ways.”
-Define the water/cementitious ratio
-Limit cement type and amount
-Limit SCM type and content
-Limit admixtures and additives
-Risk lies with the owner/designer
-Define the functional performance criteria of the element/structure
-Have plastic, hardened, and other measurable requirements
-Risk lies with the producer/contractor
As mentioned, there is no single solution that will decarbonize the concrete industry. However, performance specifications empower concrete producers to create innovative new mix designs—stacking multiple innovations together—to deliver all the performance requirements while also reducing or removing carbon from the concrete manufacturing process.
Interested in this topic? Watch our recent webinar featuring speakers from the Cement Association of Canada and Lafarge Canada.