Storing carbon in buildings to fight climate change

The quest to limit global warming and stabilize Earth’s climate hinges on achieving net-zero emissions of greenhouse gases. This goal requires balancing anthropogenic carbon dioxide emissions with greenhouse gas removal.

While traditional carbon capture and storage methods have been proposed, they often involve significant challenges and risks. A promising alternative lies in the materials we already use extensively: building materials such as concrete, asphalt, wood, and bricks.

Civil engineers and earth systems scientists from institutions like UC Davis and Stanford University have explored the ability of construction materials to act as carbon sinks.

Their findings, published in the journal Science, indicate that these materials could lock away billions of tons of carbon dioxide. Elisabeth Van Roijen, who spearheaded this research, highlights the opportunity to harness materials we already produce in large quantities to combat climate change.

Concrete, the world’s most widely used building material, emerges as a key player. By integrating carbonated aggregates and biochar—a substance derived from heating biomass waste—concrete could absorb significant amounts of carbon dioxide.

Current estimates suggest that if just 10% of global concrete aggregate production incorporated these technologies, it could sequester a gigaton of CO2 annually. Given that over 20 billion tons of concrete are produced worldwide each year, the potential impact is immense.

Concrete’s capacity to store carbon stems not only from its vast production volume but also from its long lifespan. Structures made from concrete can last for decades, ensuring that the carbon sequestered within remains stable over time.

Additionally, carbonated aggregates used in concrete and asphalt are formed by reacting certain minerals with CO2, effectively locking it away in a stable mineral form. This innovative approach could significantly enhance the role of concrete in mitigating climate change.

The study delved into various methods to enhance carbon storage in construction materials. One approach involves using magnesium oxide-based cement synthesized from forsterite, combined with biochar as a filler. This combination has demonstrated the capacity to absorb approximately 0.9 kilograms of CO2 per kilogram of cement binder, with a total storage potential of 2.6 gigatons.

Bricks, another common material, could incorporate biomass fibers to store roughly 0.8 gigatons of CO2. Additionally, using calcium hydroxide in bricks enables further mineral carbonation, fixing an additional 1.2 gigatons of CO2.

Bricks hold potential not just because of their ability to store carbon but also because of their ubiquity in construction. Globally, bricks are a staple material for buildings, and introducing carbon-storing technologies to their production could yield substantial benefits.

For instance, biomass fibers, which account for only 15% of the brick’s mass, can still contribute significantly to carbon storage. Similarly, calcium hydroxide, a common component in brick manufacturing, can undergo mineral carbonation processes to trap even more CO2.

Asphalt and bio-based plastics also contribute to carbon sequestration, albeit on a smaller scale. Asphalt binders derived from biomass and bio-based plastics have demonstrated potential, though their relatively low production volumes limit their overall impact. Nevertheless, even incremental contributions from these materials add up, reinforcing the importance of a multifaceted approach to carbon storage.

The materials used for these innovative processes often come from low-value waste streams, such as biomass residues. Transforming these waste products into valuable components of construction materials not only enhances carbon storage but also promotes economic development and supports a circular economy.

For example, biochar production from agricultural waste can provide farmers with a new revenue stream while reducing waste.

The integration of these technologies into mainstream construction practices requires further development to ensure material performance and validate net storage potential. However, many solutions are already nearing readiness for adoption. Sabbie Miller, an associate professor of civil and environmental engineering at UC Davis, emphasizes that these technologies are poised to make a significant impact if implemented widely.

In addition to economic benefits, adopting carbon-storing materials can create environmental synergies. For example, using biochar and biomass-based components reduces reliance on fossil fuel-derived materials, lowering the overall carbon footprint of construction projects. These changes also promote sustainability by encouraging the reuse of waste materials and reducing the demand for virgin resources.

The production and use of bio-based plastics, while still limited, represent another area of opportunity. These materials, derived from plant-based feedstocks, not only store carbon but also decompose more readily than conventional plastics, reducing environmental pollution. Though their current contribution to total carbon storage is modest, advances in production technologies could expand their role in the future.

The cumulative carbon storage potential of these materials is staggering. Concrete and asphalt aggregates alone account for 11.5 gigatons of storage capacity, nearly threefold the contribution of other materials.

The global production of wood, bricks, and bio-based plastics could add another 5.1 gigatons, pushing the total potential to over 16.6 gigatons. This figure represents nearly half of all CO2 emissions from human activities in 2021.

However, realizing this potential requires addressing challenges associated with material sourcing, production, and disposal. Wood, for instance, offers significant storage capacity, but its benefits depend on sustainable forest management and minimizing emissions from harvesting and processing.

Similarly, ensuring the longevity and proper end-of-life handling of materials like bio-based plastics and asphalt is essential to maximize their carbon storage potential.

The longevity of construction materials also plays a critical role. Unlike other carbon storage solutions that may be temporary, the durability of materials like concrete and brick ensures that sequestered carbon remains locked away for decades, if not centuries. This long-term storage aligns with global climate goals by providing a stable and reliable means of reducing atmospheric CO2 levels.

Moreover, the adoption of these materials aligns with global efforts to achieve a circular economy. By reusing waste materials and reducing reliance on fossil fuels, these strategies can lower greenhouse gas emissions across multiple sectors. For instance, using agricultural residues to produce biochar or biomass fibers not only stores carbon but also diverts waste from landfills, further reducing emissions.

The integration of carbon-storing building materials into construction practices represents a logical first step in addressing climate change. Unlike other carbon storage methods, this approach leverages the materials and infrastructure already embedded in the built environment. This minimizes the need for additional systems, such as pipelines for underground CO2 storage, which pose environmental risks.

The research underscores the need for collaborative efforts between industries, policymakers, and scientists to accelerate the adoption of these technologies. Investments in research and development, along with incentives for using low-carbon materials, could drive significant progress.

Elisabeth Van Roijen, now a researcher at the U.S. Department of Energy National Renewable Energy Laboratory, notes that enhancing the value of waste feedstocks through carbon storage innovations can create a win-win scenario for both the environment and the economy.

By rethinking the role of construction materials, humanity can transform the built environment into a powerful ally in the fight against climate change. With the right strategies, these materials can become not just functional components of our cities but also vital tools for securing a sustainable future.

The challenge now lies in scaling these solutions and integrating them into global construction practices, ensuring that the potential of these materials is fully realized.

Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.

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