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Abstract
Concrete alone makes up 11% of total global emissions. Delivering greener concrete faster for data centers is the best opportunity to reduce embodied carbon in the data center construction industry. We call on the data center industry to discuss and concur on standard baselines for embodied carbon reduction in concrete to measure against. We encourage companies developing these technologies to share their Environmental Product Declaration (EPD) through EC3, an open-source repository, to enable the acceleration of these technologies. Having a clear and consistent method to calculate emissions in concrete is important to understanding opportunities, decision making, and tracking progress. We would like to invite innovators, the construction industry, regulatory bodies and industry groups to collaborate with us to meet our ambitious sustainability goals.
Introduction
In accordance with our broader sustainability goals, we recognize the urgency to reduce the embodied carbon of our building materials. According to Precedence Research, global spend on data center construction is forecasted to surpass $369 billion USD by 2030. Given the magnitude of the spend, the best opportunity to reduce embodied carbon in the construction industry is to deliver greener concrete faster through robust action across the data center industry.
Concrete, steel and aluminum are responsible for 23% of total global emissions, while concrete alone makes up 11% of total global emissions (EIA Global Status Report 2018). Of the structural materials included in data center buildings, concrete has the most material variability and there are multiple pathways to decarbonize this heterogeneous material. This summary focuses on some concrete decarbonization pathways that we are pursuing.
In a concrete mix, most of the embodied carbon originates from the Portland Cement which acts as the bonding agent to give concrete a hardened property after curing. While Portland Cement typically forms ~7 to 15% of a concrete mix by weight, it can contribute ~80 to 95% of the embodied carbon in concrete.
Portland Cement production releases CO2:
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- during the extraction and transportation of raw materials to make cement
- when burning fossil-based fuels to achieve high kiln temperatures to turn limestone into cement
- as a product of the chemical reaction that occurs during cement production
Therefore, effective decarbonization of concrete can be achieved through:
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- the use of suitable cement replacements
- the improvement of cement manufacturing processes and energy sources
- increased use of blended or innovative cements
Lower carbon concrete materials available today are cost-competitive and do not result in adverse construction schedule impacts. As leaders in data center construction, we have two major approaches. The first is to design structures to use less concrete while still meeting our technical requirements. The second is to specify and deploy the lowest carbon concrete available. This includes ensuring data center builders are installing the lowest carbon concrete in the immediate, near, and long-term futures while meeting all other structural, performance, and cost criteria.
Definition
The term “Low-Carbon Concrete” is an industry term that refers to concrete which has achieved an embodied carbon reduction as compared to a fixed baseline mix (which contains average/normal amounts of Portland Cement) by industry bodies such as the National Ready Mixed Concrete Association (NRMCA). This can be achieved by either reducing the embodied carbon of individual mix ingredients, including recycled or up-cycled mix ingredients, or reducing the amount of embodied carbon-intensive ingredients in the mix.
We call on the data center industry to discuss and concur on standard baselines for embodied carbon reduction in concrete to measure against. This will facilitate consistency across the industry. We anticipate that the data center industry will reach the following phases of progress in embodied carbon reduction in concrete and will strive to partner with industry to support the development of the following technology roadmap:
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- Phase 1: Leverage existing technology. Re-use of commercially industrial waste like fly ash and slag to supplement and reduce cement usage. 2023 – 2027
- Phase 2: Accelerate emerging technology. Deprecate ordinary cement with technologies like slag-based alkali activated cement, calcium sulfoaluminate (CSA), geopolymers, recycled glass pozzolans and limestone calcined clay cement (LC3). 2026 – 2030
- Phase 3: Employ carbon sequestering cement and aggregates. New aggregates that capture carbon, graphite cement, geopolymers, and other innovations which will result in net carbon negative products. 2028 -2040
Decarbonization Strategies
Below describes how data centers might achieve embodied carbon reduction in concrete to reach the respective phases.
Phase 1
Commercially available technologies can make modest reductions of up to ~30%, compared to conventional concrete. Some Supplementary Cementitious Materials (SCMs) which can replace ordinary cement are fly ash and slag. Fly ash and slag are reactive waste products of the coal-burning and steel manufacturing industries, respectively. Mixing fly ash and powdered slag with water produces a cement like product without emitting CO2 and these can be used as direct cement replacements. Additionally, using blended cements, such as Portland Limestone Cement (e.g. Type IL cement) has a higher percentage of limestone in it which results in a blended product with less ordinary cement content. Another technology that is immediately available injects captured carbon dioxide into the concrete mix where it is trapped as it reacts, and results in a ~5% embodied carbon reduction of the concrete. Industry support is required to make this technology regionally available and viable.
Phase 2
Near-term solutions that further diminish the use of ordinary cement include technologies such as slag-based alkali activated cement, calcium sulfoaluminate (CSA), geopolymers, recycled glass pozzolans and limestone calcined clay cement (LC3) made with limestone and calcined clay, and clinker composition optimization. The carbon footprint of LC3 is ~40% smaller and the clay used is available throughout the world. These innovative solutions can stretch potential reductions up to ~70% and expand the suite of alternative cementitious materials. Those near-term solutions require testing and investment to prove concepts and then scale up. We are interested in rapidly accelerating the development and scaling of these near-term materials. We encourage companies developing these technologies to share their Environmental Product Declaration (EPD) through EC3, an open-source repository, so that we can support the acceleration of these technologies.
Phase 3
In the long-term, we are engaging with manufacturers focused on storing carbon in concrete. The manufacturers are innovating new aggregates, biogenic limestone, graphite cement, geopolymers, and other raw materials and chemical processes, which could result in net carbon negative products. Innovations that sequester or store carbon in concrete are promising for the long term, but current development pathways must be accelerated to scale capacity sooner and across expanded geographies. Direct investment in the most innovative technologies will be needed in the near term to achieve the scale necessary.
Industry Engagement
Having a clear and consistent method to calculate emissions in concrete is important to understanding opportunities, decision making, and tracking progress. We would like to invite innovators, the construction industry, regulatory bodies and industry groups to collaborate with us on these objectives:
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- Improving transparency of embodied carbon data for building materials & equipment
- Incorporating commercial-ready strategies into standard design templates
- Improve supply chain economics and scale for proven technologies by increasing demand
- Define clear taxonomy for how carbon credits are counted and by whom
- Proving out innovative materials through pilot implementation and testing, and sharing results in open forums
- Working directly with manufacturers to accelerate development for carbon storing technologies through investments, pilots, and R&D
- Engaging industry bodies to decarbonize raw materials, including concrete
This effort aims for widely available and economical supplies of supplementary cementitious materials, advanced blended cements, and innovative aggregates. These efforts can scale up the building material industries to readily and economically provide low-carbon concrete across all geographies. As designers of our data centers, we can also optimize our structural designs to reduce the materials needed to build our buildings.
Conclusions
We can strive to reduce the embodied carbon in our concrete by using suitable cement replacements, researching and testing new cement material technologies, improving cement manufacturing processes and energy sources, and reducing the overall volume of concrete we use. These challenges will be solved by an industry-wide effort while using stackable solutions which ultimately deliver significant embodied carbon reductions. We will consistently measure progress by using the phases above. This is an important step we are taking to encourage the data center industry to move faster to meet our ambitious decarbonization goals.
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