By replacing conventional concrete aggregates with carbon-based materials, scientists at Empa believe large amounts of CO₂ could be permanently stored in building products. Their concept, “Mining the Atmosphere,” aims to help reduce atmospheric CO₂ levels to 350 parts per million — roughly the 1988 benchmark.
Concrete could store considerable amounts of CO2 if conventional aggregates were replaced by pellets made from biochar. Credit: Empa
To remove CO₂ from the atmosphere is “a very energy-intensive endeavor,” noted Pietro Lura, head of Empa’s Concrete and Asphalt laboratory, in a press release. “These calculations are based on the assumption that sufficient renewable energy will be available after 2050 to remove CO₂ from the atmosphere.” Despite uncertainty about that assumption, Empa’s projections suggest that vast volumes of CO₂ could be converted into methane or methanol, then further processed into carbon-rich materials such as polymers, silicon carbide, or biochar.
Key Components of the Strategy
- Concrete as a storage medium: With its global prevalence, concrete might absorb enormous quantities of carbon. “It remains a challenge how quickly and efficiently carbon can be introduced into these materials without deteriorating their properties,” Lura said.
- Replacing high-emission materials: Conventional CO₂-emitting building resources could be phased out using carbon-enriched substitutes. Lura explains, “Carbon must be incorporated into stable materials, as direct storage can be dangerous — due to the risk of fire.”
- Silicon carbide’s role: This compound, used as a potential filler, is extremely energy-intensive but binds carbon “practically forever” and strengthens concrete. Its cost and sustainability remain open questions.
Possible Timeline
Under optimistic scenarios, up to ten gigatons of carbon per year could be captured in building materials by 2050 — once renewable energy becomes widely available. The surplus carbon, around 400 gigatons, plus an extra 80 gigatons from unavoidable emissions, might be stored within 50 to 150 years. “Nevertheless, the aim should be to remove as much CO₂ as possible from the atmosphere each year,” Lura said, adding that emissions must still be reduced to make any removal effort worthwhile.
Practical obstacles
Even with sufficient renewables, the approach demands progress in materials research, process development, and economic incentives. It is not enough to reduce greenhouse gas emissions to achieve climate targets, Empa’s researchers note. They also see potential in transporting synthetic methane — a byproduct of carbon conversion — from sun-rich regions to those needing extra energy in winter. However, the success of “Mining the Atmosphere” hinges on how efficiently carbon can be captured, processed, and integrated into long-lived building materials at scale.
While critics may see these targets as overly ambitious, proponents argue that combining carbon capture with durable building applications offers a path forward. As Lura stated, “At the same time, it is crucial to continuously minimize our emissions so that the recovery process is not in vain.”
