Cement and Concrete: Their Role and Impact in Embodied Carbon Emissions

At Firstgreen Consulting, we delve into the challenges and opportunities that various construction materials present in the context of embodied carbon emissions. In this segment, we discuss Cement and Concrete, two of the most widely used materials in the construction industry, and their significant influence on the carbon footprint of buildings.

Understanding Cement and Concrete

Despite common interchangeability in casual language, cement and concrete are unique materials, each with its distinct role in construction and embodied carbon footprint. To construct a building, professionals purchase concrete, which includes cement.

Cement, particularly ordinary Portland cement, acts as a binder with water to adhere particles of sand and rock, known as aggregate, forming concrete. The cement industry alone contributes a colossal 68.3 million metric tons of CO2e per year, placing it among the largest contributors to US-borne emissions.

Cement: The Carbon-Intensive Component

The embodied carbon in concrete largely stems from the production of cement. Approximately 60% of CO2 emissions from cement production originate from chemical reactions during clinker production, an intermediary component of cement. Given the nature of these chemical reactions, these emissions cannot be eliminated through improved energy efficiency or fuel-switching.

One possible way to reduce cement’s embodied carbon is by substituting a portion of the cement with supplementary cementitious materials (SCMs) such as fly ash and slag or using a clinker-free alternative to Portland cement.

However, the availability of high-quality SCMs is dwindling, while demand rises due to their effectiveness in reducing embodied carbon. For instance, the supply of fly ash, a by-product of coal power generation, is decreasing as coal usage for power generation diminishes.

Strategies to Reduce Embodied Carbon in Cement and Concrete

The reduction of embodied carbon in cement and concrete necessitates innovative and effective strategies. Here are a few noteworthy methods:

1. Use of High-Quality Aggregate: High-quality aggregate can reduce the cement quantity needed to produce concrete due to its superior adhesion properties. In some cases, the improved strength outweighs the carbon emissions linked to transportation, even when imported.
2. Electrification of Cement Production: Approximately 40% of cement production emissions come from burning fossil fuels to heat the kilns required for clinker production. Electrification of the cement production process and the use of alternative fuels such as biomass and renewable energy could significantly reduce these emissions.
3. Carbon Capture Techniques: Researchers are exploring the potential of carbon capture techniques that could store carbon emissions from cement kilns. While these technologies are not yet market-ready, they represent a promising solution.
4. Emerging Technologies: A wave of researchers are focusing on emerging technologies that could substantially reduce emissions during cement production, aiming to produce zero-embodied-carbon cement, or even net carbon-negative products.

While the challenges in reducing the embodied carbon of cement and concrete are substantial, the commitment to finding solutions is even stronger. As we progress, we remain hopeful about the emergence of groundbreaking technologies and strategies that will significantly mitigate these emissions and steer us toward a sustainable future.