Reviewed by Lexie CornerJan 21 2025
The new Empa initiative, Mining the Atmosphere, aims to capture excess atmospheric CO₂ and store it in construction materials such as concrete.
Concrete could store considerable amounts of CO2 if conventional aggregates were replaced by pellets made from biochar. Image Credit: Empa
Empa researchers have quantified the potential impact of this approach, estimating that five to ten billion tons of carbon could be incorporated annually into concrete aggregates. This capacity could allow for the permanent storage of the current atmospheric CO₂ surplus within 100 years of the energy transition, potentially restoring atmospheric CO₂ to climate-stabilizing levels.
To achieve the 1988 target of 350 ppm (parts per million) CO₂ concentration in the atmosphere, approximately 400 billion tons of carbon—equivalent to 1,500 billion tons of CO₂—must be removed. The researchers project that this surplus carbon could be effectively stored in construction materials like concrete by the mid-22nd century.
These calculations are based on the assumption that sufficient renewable energy will be available after 2050 to remove CO₂ from the atmosphere – a very energy-intensive endeavor. This assumption allows us to use different scenarios to analyze how realistic and efficient the concept of our Mining the Atmosphere initiative is.
Pietro Lura, Head, Concrete and Asphalt Laboratory, Swiss Federal Laboratories for Materials Science and Technology
The initiative focuses on binding excess CO₂ and repurposing it as a valuable raw material for large-scale applications.
Building Materials are Crucial
Surplus renewable energy can convert CO₂ into methane or methanol, which are then further processed into polymers, hydrogen, or solid carbon.
“Even if sufficient renewable energy is available, the central question remains as to how these huge quantities of carbon can be stored in the long term. Concrete seems predestined for this, as it can absorb enormous quantities,” explained Lura.
The researchers compared the global usage of materials such as concrete, asphalt, and plastics to the quantity of carbon that must be removed from the atmosphere, including emissions that are difficult to avoid.
“The mass of building materials required worldwide far exceeds the excess carbon in the atmosphere. However, it remains a challenge how quickly and efficiently carbon can be introduced into these materials without deteriorating their properties,” stated Lura.
The Mining the Atmosphere approach offers several advantages over traditional CO₂ reduction methods, such as underground storage. It ensures long-term stability, provides high carbon storage density, and allows decentralized application. Additionally, it can replace conventional CO₂-emitting construction materials.
“Carbon must be incorporated into stable materials, as direct storage can be dangerous – for example, due to the risk of fire. Ideally, these carbon-enriched building materials are used over several recycling cycles before they are finally disposed of safely,” said Lura.
Lura also noted that this strategy reduces CO₂ while promoting a carbon-binding economy that helps both the environment and industry.
Lura stated, “Carbon from the atmosphere can be used, for example, to produce polymers, bitumen for asphalt, or ceramic materials such as silicon carbide. In addition, other high-value materials such as carbon fibers, carbon nanotubes, and graphene could make the whole process economically viable – with concrete accounting for the largest share of carbon storage.”
Hard Carbon Rocks as an Accelerator
How long would it take to remove excess CO₂ from the atmosphere? Under ideal conditions, construction materials like concrete could potentially bind up to 10 gigatons of carbon annually. However, this capability would not be fully realized until 2050, when sufficient renewable energy is expected to become available following the energy transition.
In addition to the 400 gigatons of excess carbon, an estimated 80 gigatons from hard-to-avoid emissions would also need to be addressed by 2100. Depending on the scenario, surplus CO₂ could be absorbed into building materials over a period of 50 to 150 years, bringing atmospheric CO₂ levels down to the target of 350 ppm.
A key factor in the most optimistic scenarios is the production of silicon carbide, which can be utilized as a filler in construction materials.
“Silicon carbide offers enormous advantages, as it binds carbon practically forever and has excellent mechanical properties. However, its production is extremely energy-intensive and represents one of the greatest challenges, both in terms of cost-effectiveness and sustainable implementation,” Lura added.
Using only porous aggregate, it would take over 200 years to fully remove the anthropogenic carbon excess. A combination of porous carbon and silicon carbide presents a more viable option, enabling the storage of substantial carbon quantities in concrete while improving its mechanical stability and durability compared to conventional concrete.
“Nevertheless, the aim should be to remove as much CO₂ as possible from the atmosphere each year to achieve 350 ppm CO₂ in a realistic timeframe together with other measures. At the same time, it is crucial to continuously minimize our emissions so that the recovery process is not in vain,” said the Empa researcher.
Mining the Atmosphere
Reducing greenhouse gas emissions alone is insufficient to meet climate objectives and avoid irreversible changes to the climate system. Actively removing excess CO₂ from the atmosphere is essential. Empa's scientific initiative, Mining the Atmosphere, aims to address this by developing a global economic model and industrial sector centered on CO₂ as a raw material.
In this approach, CO₂ is first converted into simple chemicals such as methane and methanol. These compounds are further processed to replace conventional construction materials and petrochemicals. At the end of their life cycle, these carbon-rich materials would be deposited in dedicated landfills to ensure permanent carbon storage. Synthetic methane could also be used to transport energy from regions with abundant solar resources to areas experiencing energy deficits during winter.
Empa researchers emphasize that further advancements in materials research and process development are needed, particularly to maximize the utilization of decentralized and variable renewable energy sources. Additionally, achieving a carbon-neutral society will require new business models, economic incentives, and regulatory frameworks to support these efforts.
Journal Reference:
Lura, P., et al. (2025) Mining the atmosphere: A concrete solution to global warming. Resources, Conservation and Recycling. doi.org/10.1016/j.resconrec.2024.107968.