TerraFixing, a Canadian company founded in 2020, develops Direct Air Capture (DAC) technology based on temperature vacuum swing adsorption (TVSA) cycle to capture and yield high purity carbon dioxide (CO₂) from the cold dry air. This unique TVSA process allows TerraFixing’s DAC technology to have low operating energies, as low as 1 MWh per metric ton of CO₂, making it a cost-effective solution for CO₂ capture. The vision of TerraFixing is to achieve the gigaton capture scale by 2050 by developing the technologies, partnerships, and business opportunities. TerraFixing was selected as one of the top 15 teams to receive a $1M Milestone Prize in the XPRIZE Carbon Removal competition.
Challenges: carbon emissions and Direct Air Capture
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.
Direct Air Capture
Direct Air Capture (DAC) is a process that extracts CO₂ directly from the atmosphere, as opposed to industrial emissions with a high CO₂ content. The captured CO₂ can then be either permanently stored in deep geological formations, thereby achieving CO₂ removal (CDR), or used as a climate-neutral feedstock for a range of products that require a source of carbon.
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 plays an important and growing role in net-zero pathways. Capturing CO₂ directly from the air and permanently storing it removes the CO₂ from the atmosphere, providing a way to balance emissions that are difficult to avoid, including from long-distance transport and heavy industry. 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/mtCO₂e (million tons of CO₂ equivalent) 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/t.
The sociopolitical acceptance of DAC is also a challenge. Currently, there is no established market for carbon removal, and the demand for carbon removal is not yet sufficient to support the large-scale deployment of DAC. Some advocates worry the carbon capture process may not be scaled up fast enough to make an impact. However, the demand for carbon removal is expected to increase as more countries and companies set net-zero targets and seek to offset their emissions. In addition, governments and other stakeholders must provide substantial funding and support.
Direct air capture companies
Several companies, such as Carbon Engineering, Climeworks, Heirloom, Noya, Mission Zero, Carbyon, Sustaera, and Verdox, are developing DAC technologies.
Carbon Engineering DAC technology is an engineered mechanical system that extracts CO₂ from the air using a combination of fans, filters, and chemical reactions. The captured CO₂ is then compressed and stored underground or reused. Carbon Engineering’s DAC technology is capable of capturing millions of tons of CO₂ annually, and individual DAC facilities can be built to capture one million tons of CO₂ annually.
Climeworks specializes in DAC technology that extracts CO₂ from the air using a solid sorbent. The captured CO₂ is then released through a regeneration process, while the sorbent material is reused. Climeworks has developed several DAC plants worldwide and is working to scale up its technology to capture millions of tons of CO₂ annually. The company operates the largest operating DAC plant, Orca, in the world. The plant is located in Iceland and is capable of drawing down the volume of carbon dioxide emissions equivalent to approximately 870 cars annually.
Heirloom uses limestone (CaCO₃) instead of synthetic sorbents to capture CO₂ from the air and store it safely and permanently. Limestone is heated in renewable-energy powered calciners to remove CO₂ and produce Ca(OH)₂ sorbents from the hydration of CaO powders. Ca(OH)₂ sorbents are placed on vertically stacked trays, and algorithms are used to optimize their capacity to absorb CO₂ in different environmental conditions. Heirloom’s DAC technology accelerates the natural property of limestone, reducing the time it takes to absorb CO₂ from years to just three days. The company claims that its technology has the lowest peer-reviewed, at-scale cost of any direct air capture technology on the market.
Noya has developed a unique DAC technology that combines the existing pieces of industrial cooling towers with solid CO₂ sorbents. This transforms industrial cooling towers into CO₂ capture machines, which radically reduces the upfront capital costs and installation time required to perform direct air capture. Therefore, Noya’s approach to DAC will enable them to scale quickly and provide low-priced carbon removal in the near-term.
Mission Zero has developed a DAC technology that continuously captures CO₂ from the air with low energy consumption. Mission Zero uses a well-established electrodialysis technology to capture CO₂ from the air and turns CO₂ into carbonic acid (H₂CO₃), which dissociates into HCO₃⁻ and proton (H⁺). The H₂CO₃ solution is circulated through an electrodialysis cell, which separates HCO₃⁻ from the absorbent solution by passing it through an anion-exchange membrane into a second absorbent solution, where 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.
Carbyon develops a fast swing process by means of a continuously rotating drum to realize a low-cost, energy-efficient DAC technology. The rotating drum comprises activated carbon fiber membranes. The surface of fibers are functionalized with a monolayer of amines that are used as CO₂ adsorbents. Such a thin surface sorbent allows a rapid CO₂ absorption at ambient temperature and fast regeneration below 100 ºC. Thereby, one cycle of absorption and regeneration occurs in less than 5 seconds. The fast swing CO₂ capture process is the key to lower the energy consumption as well as the cost of the machine.
Sustaera has developed monolithic structured material assemblies that use renewable electricity to remove CO₂ directly from the air. The monolithic structured material assembly has a monolithic substrate with a honeycomb-like structure positioned between two mesh electrodes. The monolithic substrate’s channel walls are coated with layers of conductive carbon desorption and sodium carbonate (Na₂CO₃) sorbent. The Na₂CO₃ sorbent absorbs CO₂ from the airflow within the channels until they become saturated. To regenerate sorbent, the conductive carbon desorption layer receives renewable electricity input and in-situ heats the sorbent layer to quickly liberate CO₂ at temperatures below 120 ºC in a few minutes.
Verdox has developed electroswing adsorption cells with patterned electrodes that contain quinone materials to capture CO₂ from air and emission sources like aluminum production. The patterned electrode comprises conductive carbon scaffold which is coated with electroactive quinone materials and extends into a polymer gel electrolyte to capture and liberate CO₂ by applying a current at select voltages in ambient temperature. Verdox’s electrochemical carbon removal technology offers a more energy-efficient approach to capturing CO₂ compared to traditional carbon capture technologies. The latter often require large amounts of heat and have inherent inefficiencies.
TerraFixing has developed a DAC technology based on a simple temperature vacuum swing adsorption (TVSA) cycle to capture CO₂ directly from cold, dry air by using low-cost Li-X or Na-X zeolite adsorbents.
Zeolites are readily available industrial materials. They have a high surface area of over 800 m²/g. However, zeolites have been ruled out as potential materials for direct air capture due to the fact that zeolites are typically hydrophilic and preferentially adsorb water over CO₂ when exposed to both. Before effective CO₂ absorption can occur with zeolites, the amount of water in the air must be reduced. However, water separation from air is an energy-intensive process.
TerraFixing has developed a DAC system that enables low-cost zeolite adsorbents to efficiently adsorb CO₂ from cold, dry air and regenerates the adsorbents with minimal energy consumption. Their DAC plants can be located in cold, dry environments such as Canada, Norway, Alaska, Russia, Finland, Greenland, and Antarctica.
TerraFixing Direct Air Capture technology
The diagram below depicts TerraFixing’s DAC system.
The system comprises a particular filter, a water capture bed, a CO₂ adsorbent bed, a heater, a vacuum pump, a water guard, and fans. The system is modular and scalable because it can be contained in a container.
- Particular filter
The particular filter removes solid particles within the input air using a known technology such as grates, electrostatic, or fiber filters.
- Water capture bed
The water capture bed is filled with silica gel to remove water from the filtered airflow. Silica gel does not adsorb CO₂ in significant quantities.
- CO₂ adsorbent bed
The CO₂ adsorbent bed contains Li-X or Na-X zeolite adsorbents that capture CO₂ via surface adsorption. Using monolithic adsorbent structures allows a low pressure drop across the bed below 500 Pa in the direction of airflow.
The heater heats the adsorbent bed during CO₂ desorption.
- Vacuum pump
The vacuum pump reduces the internal pressure of the CO₂ adsorbent bed. During the blowdown process, it removes weakly adsorbed undesirable air components, such as N₂ and O₂. During the CO₂ desorption process, it extracts CO₂ from the adsorbent bed once the bed has been sufficiently heated.
- Water guard
The water guard, which is located downstream of the CO₂ adsorbent bed and contains desiccant, ensures that the air entering the CO₂ adsorbent bed during the pressurization step is dehydrated.
TerraFixing temperature vacuum swing adsorption
TerraFixing DAC technology uses a 5-step temperature vacuum swing adsorption (TVSA) cycle to capture and produce high purity CO₂.
The 5-step TVSA cycle consists of the following subsequent steps:
1. Adsorption: Adsorbing CO₂ from the cold, dry air on the surface of zeolite adsorbents below 0 ºC until the adsorbent bed reaches its adsorption capacity;
2. Blowdown: Using vacuum to remove undesirable air components of N₂ and O₂ that are weakly adsorbed to the adsorbents;
3. Evacuation: Using vacuum and heat to desorb CO₂;
4. Pressurization: Pressurizing the adsorbent bed to adsorption pressures with the dry air; and
5. Water capture bed regeneration: Regenerating the desiccant in the water capture bed by reversing the cold, dry airflow so that the hot adsorbents cool down and heat the airflow, which then passes through the water capture bed to regenerate the desiccant.
After the water capture bed regeneration step, the adsorption step is repeated.
- Step 1: Adsorption
The diagram below depicts the adsorption process.
Input air is first passed through a particulate filter to remove any solids that may be present. The filtered air is then passed through a water capture bed containing desiccant that removes water from the air. The resulting air is then passed through the CO₂ adsorbent bed. Air exiting the CO₂ adsorbent bed contains significantly less CO₂ than the input air. The adsorption step proceeds until the adsorbent bed reaches its adsorption capacity.
- Step 2: Blowdown
The blowdown step begins by isolating the CO₂ adsorbent bed from the fan and input air source to create an airtight system, as depicted in the diagram below.
The vacuum pump then lowers the pressure within the CO₂ adsorbent bed below ambient pressures. Weakly adsorbed components such as N₂ and O₂ are removed from the adsorbent bed. Strongly adsorbed CO₂ remains on the adsorbent.
- Step 3: Evacuation
After removing undesirable air components, as depicted in the diagram below, heat and vacuum are applied to the CO₂ adsorbent bed to desorb and extract CO₂. The heater heats the adsorption bed up to 300 ºC.
- Step 4: Pressurization
After CO₂ extraction, the vacuum pump and heater are disconnected from the CO2 adsorbent bed. As depicted in the diagram below, the pressure of the CO₂ adsorbent bed is returned to atmospheric pressure by adding air that first passes through the water guard, which removes any water from the air. The dried air then passes through the CO₂ adsorbent bed at low speed to allow it to absorb the sensible heat from the adsorbent.
- Step 5: Water capture bed regeneration
The heated dry air in the CO₂ absorbent bed then passes through the water capture bed to regenerate desiccant and then exits the apparatus, as depicted in the diagram below.
In this manner, the reverse airflow becomes warm by cooling the hot CO₂ adsorbent bed, which has been heated during the above evacuation step. The hot reverse airflow then regenerates the desiccant within the water capture bed. This is advantageous, as the adsorbent bed must be cooled before the next cycle. Therefore, this reverse airflow ensures that the apparatus is regenerated between cycles with minimal downtime and reduced energy cost.
- WO2022109746A1 Direct air capture and concentration of co2 using adsorbents
Carbon offset credit market
The market value of carbon offset credits varies widely. In current carbon markets, the price of one carbon credit can range from a few cents per metric ton of CO₂ emissions to $15/mtCO₂e (metric tons of CO₂ equivalent) or even $20/mtCO₂e. However, the voluntary carbon offset market, which was worth about $2 billion in 2021, is projected to grow to $10-40 billion by 2030, transacting 0.5-1.5 billion tons of CO₂ equivalent, as opposed to the current 500 million tons. The total value of carbon credits produced and sold to help companies and individuals meet their de-carbonization goals could approach $1 trillion as soon as 2037.
TerraFixing’s DAC technology is optimized for cold dry climates and requires operating energies as low as 1 MWh per metric ton of CO₂. Their DAC plants can be located in cold dry environments such as Canada, Norway, Alaska, Russia, Finland, Greenland, and Antarctica. Their technology can capture and concentrate 9.7 metric tons of CO₂/day from the air (for a 300 MW power plant). TerraFixing’s DAC technology can be incorporated neatly into the Allam Cycle, which can power their DAC process.
Plug and Play Tech Center has invested in TerraFixing in 2022.
Sean Wilson is CEO.