Carbon dioxide, a main driver of climate change, is naturally drawn into oceans, trees, soil, and other carbon sinks. This week, we spoke with Dr. Sabbie Miller, a researcher at UC Davis, who’s working to sequester carbon in buildings with a material called biochar. For a transcript, please visit https://climatebreak.org/sequestering-carbon-in-building-materials-with-dr-sabbie-miller/
Introduction to the Solution
UC Davis researchers are examining a novel approach to combating climate change: turning our buildings into carbon sinks. The solution is based on incorporating biochar, a carbon-rich material obtained from plant material, into common construction materials like concrete, brick, and asphalt. By embedding carbon directly into long-lasting infrastructure, this approach reduces atmospheric CO₂ and also transforms one of the most carbon-intensive industries in the world into a tool for climate mitigation.
Background: How Carbon Storage in Building Materials Works
Biochar is created through pyrolysis, a process involving heating organic material, such as crop residues or wood waste, in a low-oxygen environment. This process locks in carbon that plants absorb during photosynthesis and prevents it from being re-released into the atmosphere through decay or burning.
The research team at UC Davis, headed by Professor Sabbie Miller and Dr. Elisabeth Van Roijen, proposes the use of biochar as a partial replacement for the materials in concrete and other construction compounds. Since more than 20 billion tons of concrete are produced every year by the construction sector, substituting 10% of that with biochar-based mixtures could store up to 1 gigaton of CO₂ annually, or the equivalent yearly emissions from Japan.
Unlike temporary carbon storage methods, like soil burial, embedding biochar in durable infrastructure ensures long-term sequestration, potentially spanning decades or even centuries. It also leverages the global scale of construction as a medium for climate action.
Advantages of This Solution
Apart from net carbon emissions reduction, the introduction of biochar-enriched building materials has tangible engineering benefits. It has been found that the addition of biochar can enhance thermal insulation, fire resistance, and durability in some uses. The process also fits well within the circular economy principles because of the organic waste used and reduced need for virgin materials.
Because construction is already a high-volume, resource-intensive industry, integrating biochar into existing supply chains could make climate-positive practices scalable and economically viable without requiring dramatic infrastructure overhauls. Equally important, this solution provides dual benefits: supporting both carbon sequestration and the development of sustainable materials.
Drawbacks and Critiques
The approach faces several scientific and logistical obstacles despite such a promising premise. Producing biochar requires energy in quite significant quantities, with sourcing biomass at large scales risking unforeseen ecological impacts such as nutrient depletion or habitat disruption. Some critics even ask whether its broad adoption might inadvertently encourage the removal of older buildings in favor of the construction of newer, carbon-storing ones, offsetting any climate gains.
Another factor is the life cycle of the biochar-infused materials themselves. While they can store carbon for decades, it remains undetermined how these materials at the end of a building's life are to be managed to avoid re-release of CO₂. Future policy frameworks and recycling technologies will be required to address these challenges if there is to be long-term effectiveness.
About the Guest
Dr. Sabbie Miller is an Associate Professor of Civil and Environmental Engineering at UC Davis. Her research focuses on sustainable infrastructure materials, life-cycle assessment, and reducing the environmental footprint of the construction industry.
Further Reading
For a transcript, please visit https://climatebreak.org/sequestering-carbon-in-building-materials-with-dr-sabbie-miller/
Ethan: I’m Ethan Elkind, and you’re listening to Climate Break – climate solutions in a hurry. Today’s proposal? Locking carbon into buildings using biochar. Biochar is a charcoal-like material made by heating plant waste with little or no oxygen. Instead of releasing that carbon into the atmosphere, researchers like Dr. Sabbie Miller at UC Davis are finding ways to embed it safely inside building materials.
Dr. Miller: Biochar is currently our most… consumed, uh, carbon dioxide removal material that's on the market. Um, so there's a bunch of different types of composites that are trying to integrate into the conventional material itself. So plastic composites with biochar, brick composites with biochar, concrete composites with biochar.
Ethan: Miller’s UC Davis team studies how much biochar can be added without weakening the structure.
Dr. Miller: People are looking at biochar as like teeny tiny replacements of part of that cement, or teeny tiny replacements of part of that aggregate so that we don't compromise the performance of the concrete, but we do get some carbon storage within the material.
Ethan: Globally, we produce over 20 billion tons of concrete each year. So even a small share made with biochar could lock away huge amounts of carbon – and public policy support could help that shift happen faster.
Dr. Miller: If we have governments that are willing to invest in materials that have lower carbon dioxide emissions, are actually carbon storing, they can actually create enough of a market demand for our production chains to start to change.
Ethan: To learn more about embedding carbon in building materials, visit climatebreak.org.