Cement is vital to modern construction. Building Information Modeling (BIM) technology is ubiquitous in global building and infrastructure projects. Cement is a significant source of industrial CO2 emissions and contributes 5% of global human greenhouse gas emissions. As global construction grows, so does the demand for cement, which threatens climate goals. Decarbonized cement  or carbon capture cement offers a promising solution to this dilemma. But what exactly does decarbonized cement entail, and how does it function?

Understanding cement's carbon footprint

The basics of cement production

To understand decarbonized cement, we first must understand why traditional cement is so carbon-intensive. Portland cement is the most common type of cement. Manufacturers heat a mix of limestone (calcium carbonate), clay, and sand in large kilns to make it. This process involves two significant sources of CO2 emissions:

1. Fuel Combustion (40%): The kilns heat the materials to up to 1450°C, usually using coal or pet coke, which releases a substantial amount of CO2.
2. Calcination Reaction (50%): This chemical process converts limestone to quicklime (calcium oxide), releasing CO₂ as a by-product.

The remaining 10% of emissions come from the electricity used in production and cement transportation.

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The challenge

Sustainable building materials are essential for reducing the environmental impact of the construction industry. Cement production, a key component of many building materials, is a significant contributor to industrial CO2 emissions.

Pathways to decarbonization

Decarbonizing cement requires a complex approach. It needs new technology, shifts in demand, and supportive policies. Here are some of the key strategies:

Reducing cement demand

1. Material-Efficient Design: Strategies that reduce cement use can reduce emissions. For example, the New York Freedom Tower used 40% less cement because of a material-efficient design.
2. Substituting with Low-Carbon Alternatives: Using materials like cross-laminated timber (CLT) instead of concrete can cut carbon emissions. Studies show a 40% reduction when using CLT instead of steel or concrete for multi-story buildings.
3. Extending Building Lifespan: Reusing and reinforcing existing buildings can double their lifespan, reducing the need for new construction and the demand for cement.

Technological innovations

1. Alternative Fuels: Fueling cement kilns with waste, scrap tyres, and sewage sludge can reduce emissions. The reduction is usually tiny, but these alternative fuels are in use and are viable short-term solutions.
2. Clinker Substitution: Clinker, a key cement component, can be partially replaced with materials like fly ash, metal slag, or calcined clay. This substitution could save up to 1.3 gigatonnes of annual CO2 emissions.
3. Carbon Capture and Storage (CCS): Grasping CO2 emissions from cement production before they enter the surroundings is a promising technology. The apprehended CO2 can be safely stored underground, helping to reduce environmental impact, or it can be repurposed to fuel other industrial processes, contributing to sustainable and eco-friendly practices. Yet, the high cost and need for extensive infrastructure pose challenges to widespread adoption.
4. Injecting sustainably sourced CO2 into Concrete: Technologies like CarbonCure inject DAC CO2 into concrete during production. This enhances the material durability and sequesters the CO2 captured from ambient air.

Long-term innovations

1. Electrolysis and Hydrogen Application: Sublime Systems is developing an electrochemical process that uses non-carbonate rocks and industrial waste to produce cement without releasing CO₂.
2. Nature-Based Solutions: Companies like Biomason use microorganisms to produce cement without needing high-temperature kilns, reducing emissions by 75%.
3. Innovating Traditional Processes: Brimstone has created a method to produce cement from basalt and other calcium-bearing silicate rocks that do not release CO2 during production. When combined with carbon sequestration, this process can result in carbon-negative cement.

The role of policy and collaboration

Decarbonizing cement requires more than new technology. It requires teamwork among governments, industries, and investors. We must have policies that support innovation. These policies should provide financial incentives and set clear standards. These policies are essential to decarbonizing cement.

Government initiatives

1. Carbon Pricing: Systems like the EU Emissions Trading System (ETS) create a financial incentive for reducing CO2 emissions by putting a price on carbon.
2. Regulatory Support: Policies that streamline the approval process for new cement technologies and materials can accelerate adoption.
3. International Collaboration: Initiatives like the Industrial Deep Decarbonization Initiative (IDDI) aim to obtain commitments from countries to adopt low-carbon concrete procurement policies.

Industry and investment

1. Corporate Commitments: The First Movers Coalition's companies will buy from zero-carbon suppliers, creating a demand for decarbonized cement.
2. Investment in Innovation: Funding for research and development of new technologies is crucial. Startups and established companies alike need capital to scale their innovations.

Decarbonized cement is critical to cutting the construction industry's carbon footprint. We can cut cement emissions and build a sustainable future by combining tech, demand reduction strategies, and supportive policies. The path to decarbonized cement is complex, and it requires many stakeholders to collaborate. But the potential benefits for the planet are immense.

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