Mission Zero, a UK cleantech company founded in 2020, develops a low-cost Direct Air Capture (DAC) technology to capture carbon dioxide (CO₂) directly from the air by leveraging the existing, scaled and mature technologies of cooling towers and electrochemical water purification. The Mission Zero’s DAC consumes less than 800 kWh per ton of separated CO₂, which is much lower than other DAC technologies based on amine sorbent or carbonate calciner, which consume between 1,500-2,000 kWh per ton of CO₂.
(This article contains 6 diagrams and 1948 words.)
Challenges: carbon emissions and Direct Air Capture
Carbon emissions
Since the early 1900s, carbon dioxide (CO₂) levels in the atmosphere have increased by 50% due to human activities. When fossil fuels (such as coal, oil, and natural gas) are burned for energy production, transportation, and industrial processes, CO₂ is released into the atmosphere. This excess CO₂ acts as a greenhouse gas, trapping heat and causing the air and ocean temperatures to rise. CO₂ emissions play a crucial role in driving climate change.
This warming effect has caused the global average temperature to rise by about 1.1 ºC since the pre-industrial period. This has led to rising in the frequency and intensity of extreme weather events, melting of polar ice caps and glaciers and rising sea levels, shifts in species ranges and increased risk of species extinction, agriculture and food security, and ocean acidification.
To mitigate these impacts, the Paris Agreement aims to limit global warming to well below 2 ºC above pre-industrial levels. The Intergovernmental Panel on Climate Change (IPCC) estimates that a “carbon budget” of about 500 GtCO₂, which corresponds to about ten years at current emission rates, provides a 66% chance of limiting global warming to 1.5 ºC.
What is Direct Air Capture?
Direct Air Capture (DAC) is a process that extracts diluted carbon dioxide (CO₂) directly from the atmosphere, as opposed to industrial emissions with a high CO₂ content. The captured CO₂ can then be either utilized in various industrial applications or buried to prevent its release back into the atmosphere.
The basic principle of DAC involves using large-scale machines or facilities equipped with specialized filters or sorbents which are designed to attract and bind with CO₂ molecules from the air while allowing other gasses, such as nitrogen and oxygen, to pass through. After the CO₂ is captured, it is separated from the sorbent through a regeneration process, resulting in the release of CO₂.
DAC technology employs a variety of methods, but chemical sorbents or solvents are typically used to capture CO₂. These sorbents can chemically react with CO₂ to form solid compounds or dissolve the CO₂ in a solvent. The captured CO₂ is then released from the sorbent or solvent via heating or other processes, allowing for its storage or utilization.
Direct air capture technology challenges
DAC has seen a surge in interest and investment over the past few years, and a growing number of companies are entering the market due to the realization that carbon removal will increasingly be needed to meet national and global climate goals, as well as the advantages of DAC relative to other carbon removal technologies. However, this technology is still in its infancy and faces several challenges that are stunting its global adoption and deployment.
One of the main challenges is that CO₂ is present in the air at a much lower concentration than other commonly targeted sources, such as flue gasses resulting from energy generation and industrial processes. This makes it technically challenging and requires a lot of energy.
As carbon dioxide removal from ambient air is an energy-intensive process, DAC technology is more expensive per ton of CO₂ removed than many mitigation strategies and natural climate solutions. Today, the price range for DAC ranges between $250 and $600. By the end of this decade, however, the cost of DAC technology is projected to fall to $250-$300 per ton for a multi-megaton capacity range. If further industrialization is accomplished within the ecosystem of this emerging industry, prices may fall to between $100 and $200.
The sociopolitical acceptance of DAC is also a challenge. Some advocates worry the carbon capture process may not be scaled up fast enough to make an impact. To implement DAC on a large scale, governments and other stakeholders must provide substantial funding and support.
Mission Zero Technology
Mission Zero has developed a DAC technology that continuously captures CO₂ from the air with low energy consumption. The technology utilizes the existing, scaled and mature technologies of cooling towers and electrochemical water purification.
Mission Zero uses a first absorbent solution to absorb CO₂ from the air and turns CO₂ into carbonic acid (H₂CO₃), which dissociates into HCO₃⁻ and proton (H⁺). The CO₂-captured absorbent solution is circulated through an electrodialysis cell, which separates HCO₃⁻ from the first absorbent solution by passing it through an anion-exchange membrane into a second absorbent solution. HCO₃⁻ anions recombine with protons in the second absorbent solution to form carbonic acid, which readily decomposes into CO₂ in the release vessel where CO₂ is collected and stored.
The most significant benefit of Mission Zero’s DAC technology is that the release of the captured CO₂ requires minimal energy due to the fact that carbonic acid is unstable at room temperature. Other DAC technologies based on an amine sorbent or carbonate calciner sorbent, on the other hand, require between 1,500-2,000 kWh per ton of captured CO₂.
Mission Zero direct air capture
The diagram below depicts the system of Direct Air Capture of Mission Zero.