Alithic, an American cleantech startup founded in 2023, has developed an energy-efficient Direct Air Capture (DAC) technology. Their process uses an aqueous solution and industrial solid waste to capture atmospheric CO₂, sequestering it in valuable calcium carbonate (CaCO₃) by-products. Notably, Alithic's technology requires less than 200 kWh per ton of CO₂ captured, significantly outperforming traditional DAC methods that are often criticized for high energy consumption.
(This article contains 2 diagrams and 1372 words.)
Challenges: carbon emissions
Since the early 1900s, atmospheric carbon dioxide (CO₂) levels have surged by 50% due to human activities, primarily the combustion of fossil fuels for energy production, transportation, and industrial processes. This excess CO₂ acts as a greenhouse gas, trapping heat and causing air and ocean temperatures to rise. The resulting warming effect has elevated the global average temperature by approximately 1.1 ºC since the pre-industrial period.
This increase of the global average temperature has led to a cascade of environmental impacts, including more frequent and intense extreme weather events, melting polar ice caps and glaciers, rising sea levels, shifts in species ranges, increased risk of species extinction, challenges to agriculture and food security, and ocean acidification.
The Intergovernmental Panel on Climate Change (IPCC) has calculated a critical "carbon budget" to address global warming. This budget, estimated at roughly 500 gigatons (GT) of CO₂, represents the maximum amount of CO₂ that can be emitted while maintaining a 66% probability of limiting global temperature rise to 1.5 ºC above pre-industrial levels. At current emission rates, this budget would be exhausted in approximately a decade, highlighting the pressing need for swift and significant reductions in CO₂ emissions.
AlithicTechnology
Direct Air Capture (DAC) is a technology that employs large-scale installations equipped with specialized filters or sorbents to extract CO₂ directly from the atmosphere. Once captured, CO₂ is isolated and can be either stored underground or utilized as a climate-neutral raw material for various applications.
DAC faces significant challenges due to its high energy requirements and associated costs. The process is inherently energy-intensive because of the low concentration of CO₂ in the atmosphere (less than 0.08%), necessitating continuous air movement through capture agents. Furthermore, many DAC technologies rely on capture agents such as CaO or liquid chemicals that typically demand high temperatures to release pure CO₂ and regenerate the agent. These factors contribute to the current high costs of DAC, which range from $250 to $600 per ton of CO₂ equivalent, impeding the rapid and widespread deployment of DAC systems.
Alithic has developed an energy-efficient and cost-effective DAC system that utilizes a sodium carbonate (Na₂CO₃) aqueous solution and industrial solid wastes to capture and sequester atmospheric CO₂.
The process involves using the Na₂CO₃ solution to leach fly ash, bottom ash, and iron and steel slags. This leaching process accomplishes two key objectives:
- It sequesters atmospheric CO₂ by producing calcium carbonate (CaCO₃) as a by-product. This CaCO₃ serves as a valuable Supplementary Cementitious Material (SCM) that can replace 5-20% of cement in construction.
- It directly regenerates the alkaline solution under mild conditions for CO₂ capture. This eliminates the need for a high-temperature regenerating process, which is typically required in many other DAC technologies.
This innovative approach combines CO₂ capture, sequestration, and solvent regeneration in a single, efficient process, while also producing a useful by-product for the construction industry.
How Alithic captures and sequesters atmospheric CO₂
The diagram below depicts the Alithic DAC system, which comprises a carbonation reactor, a CO₂ absorption column, a dissolution reactor, a degassing precipitation reactor, and filter devices.