In the quest for reduced greenhouse gas (GHG) emissions, everyone has a role to play. In the concrete industry, this includes everyone from manufacturers to contractors, and from trade associations to governments. Here is a review of some of the major initiatives impacting concrete’s sustainability.

PCA’s Roadmap to Carbon Neutrality

The Portland Cement Association (PCA) released its "Roadmap to Carbon Neutrality" in 2021. It cites opportunities to reduce emissions at five steps: Clinker, Cement, Concrete, Construction, Carbonation. The PCA refers to these as the “5 Cs.”

The Report’s Executive Summary states, “The PCA Roadmap involves the entire value chain starting at the cement plant and extending through the entire life cycle of the built environment to incorporate the circular economy.” The goal is to seek contributions to carbon neutrality in every phase of the value chain.

Concrete Zero

ConcreteZero is a major program of the Climate Croup, an international non-profit founded in 2003. The organization maintains offices in New York City, London, New Delhi, Beijing, and Amsterdam. Its membership rolls include more than 500 global companies in 175 international markets.

ConcreteZero is a global initiative of forward-thinking organizations promoting net zero concrete. It is a product of a partnership between the Climate Group and the World Green Building Council.

Participants commit to various emissions targets over the coming decades. “Businesses that join ConcreteZero commit to using 100% net zero concrete by 2050, with two ambitious interim targets of using 30% low emission concrete by 2025 and 50% by 2030.”

California: Net Zero by 2045

Executive Order B-55-18 requires California carbon neutrality by 2045. Gov. Gavin Newsom signed Senate Bill 596 in September 2021. It requires the California Air Resources Board (CARB) to seek ways to reduce emissions. reduce greenhouse gas (GHG) emissions to 40% below 1990 baseline levels by 2035. The bill further requires the industry to achieve net-zero emissions by 2045.

The Achieving Carbon Neutrality in California Report “examines potential energy system and technology transformations to achieve carbon neutrality.” Scenarios examined suggest the potential for significant reductions in direct emissions by 2045. Compared to the 1990 baseline, they are: High CDR (80%), Balanced (87%), and Zero Carbon Energy (92%). Each scenario embraces a “high electrification” approach.

Are Timely Net Zero Goals Achievable?

The “Net Zero by 2050” mantra reverberates across all industrial sectors. At the same time, it is important to contemplate to what degree this high standard is achievable. In some instances, net zero emissions depends on technology not yet perfected, scaled, or even invented yet.

On the other hand, technological innovation accelerates. Sensors deliver massive amounts of data analyzed by powerful computers. Industry 4.0 – the so-called Fourth Industrial Revolution – perfects production processes. Now, in the 2020s, artificial intelligence (AI) injects hope for further advances.

Circularity is key

In November 2022, the World Economic Forum published “Circularity: A key enabler to reach net-zero in cement and concrete.” The report discusses key sources for reduced emissions.

Enhanced design of infrastructure and buildings

It is imperative that architects and engineers give sustainability its due during the design process. This is possible in a variety of areas:

• Modular design that focuses on the need for adaptable, flexible spaces

• Refurbish existing structures to reduce the demand for new

• Embracing closed cycles of use and reuse

An embrace of materials with lower emissions

Circularity also requires a transition to low-emissions products whenever it is feasible. For example, by 2050, alternate fuels like biomass could meet 40% of the cement industry’s energy needs. Increased use of supplementary cementitious materials (SCMs) reduces the need for high-emissions clinker.

Repurposing captured carbon

It is possible to inject carbon dioxide (CO2) into concrete mixes to sequester it. This increases hydration while enhancing strength. In a segment that aired December 7, 2023, Boston’s WBUR reported on the country’s first commercial-scale, direct-air-capture (DAC) plant.

The Tracy, CA, facility offers a modest capacity of 1,000 tons of CO2 per year. Stacked trays of powdered limestone remove CO2 from air passing through the plant. Robots move the trays to a kiln where heat separates the carbon from the limestone. This allows for reuse of the trays. Renewable energy powers the process.

Nova Scotia’s CarbonCure developed a method for infusing concrete mixes with CO2. It has already delivered 800 of its systems in 35 countries. Collectively, these installations have already sequestered more than 379,000 metric tons of CO2. A cement plant in San Jose, CA, is one of those installing the CarbonCure tech in the United States.

At the end of the concrete’s service life, breaking it up increases the surface area exposed to the air. This amplifies carbonation, removing additional CO2 from the atmosphere in the process. Researchers continue to look for ways to amplify CO2 uptake by crushed concrete.

The industry’s quest for net-zero concrete continues. A recent McKinsey report cites promising developments in:

• Cutting emissions by reducing use of clinker in Portland cement

• Sequestering carbon dioxide in concrete, simultaneously strengthening it

• Developing carbon capture technologies for cement plants

Cost is inevitably a challenge as new technologies emerge. For example, McKinsey estimates that “building low-emissions cement production capacity and installing CCUS equipment” could increase costs by 45%. Ideally, technological refinements, government incentives, and scaling combine in the assault on cost.

About PACA

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