Direct Air Capture: Removing Carbon From Atmosphere

Climate change mitigation scenarios that align with the Paris Agreement’s aim of limiting global warming commonly rely on carbon dioxide removal and negative emissions technologies. Direct air capture (DAC) is a technology that involves extracting CO2 directly from the air through engineered systems. DAC can work with other negative emissions technologies. Together, they can help reduce CO2 emissions from various sources, including mobile and dispersed ones.

The outcome of the captured CO2, whether stored, reused, or utilized, is crucial. Decisions regarding the energy and materials involved in the DAC process also play a significant role. Together, they determine whether the overall process achieves emissions.

In recent years, DAC has experienced notable advancements, with commercial entities operating in the market promising opportunities for significant expansion.

DAC Technology for Zero Emission

As per IEA Net Zero Emissions by 2050, direct air capture (DAC) technologies are crucial, projected to capture over 85 million tonnes (Mt) of CO2 by 2030 and approximately 980 MtCO2 by 2050. This represents a significant increase from the current capture level of around 0.01 MtCO2. Currently, 18 operational DAC facilities are located in Canada, Europe, and the United States. The development of the first large-scale DAC plant capable of capturing up to 1 MtCO2 per year is underway and expected to commence operations in the United States by the mid-2020s. This milestone signifies a significant leap in the advancement and deployment of DAC technology.

Why is There an Urgency for Carbon Removal?

The present CO2 concentration in the atmosphere is about 420 ppm or 3,237 GtCO2 (CO2.Earth, 2022). 20 GtCO2 of CO2 capture and removal per year would be required by the end of the century to keep the temperature rise under 2°C (National Academies of Sciences, 2018). Global carbon dioxide capture and storage is 0.0385 GtCO2 per year (Global CCS Institute, 2018). Thus, achieving this goal would take roughly 21,000 years if things go at the current pace. So, it requires quick measures. This number also includes the current DAC capacity of 9,000 tCO2 per year.

Assuming a linear growth in the net global CO2 capture and storage capacity, the goal is to increase it from the current 0.0385 GtCO2 per year to 20 GtCO2 per year by the end of the century. This would require removing an estimated 798 Gt of CO2 from the atmosphere. At the current rate of 0.0385 GtCO2 removal per year, reaching the goal would take around 21,000 years. Hence, deploying DAC plants globally is urgent, which could meet the Paris Agreement’s goal of keeping the temperature rise under 2°C.

According to CO2.Earth (2022), the current atmospheric CO2 concentration is approximately 420 ppm or 3,237 GtCO2. To limit the temperature increase to under 2°C, it is estimated that by the end of the century, we will need to capture and remove 20 GtCO2 of CO2 annually (National Academies of Sciences, 2018).

Forecast Direct Air Capture and Storage

To reach the net-zero emissions target by 2050, it was forecast that direct air capture and storage (DAC+S) technology would need to remove 71 million metric tons of carbon dioxide equivalent (MtCO₂e) in 2030. That figure should increase to 633 MtCO₂e in 2050 to achieve global net-zero.

Figure: Emission Removal

How do Solid Sorbent Direct Air Capture Systems Work?

Solid sorbent direct air capture (S-DAC) systems use solid adsorbents functionalized with amines to capture atmospheric CO2. Here’s how they work:

1. Exposure to Air: The solid sorbent is exposed to the air, allowing it to come into contact with atmospheric CO2.
2. Selective Adsorption: It selectively adsorbs CO2, allowing other air components to pass through.
3. Regeneration: Once the sorbent is full, the CO2 is released from it, usually via heat application. This process, called regeneration, allows the sorbent to be reused.
4. Storage: The captured CO2 is then separated from the sorbent and stored in durable forms of storage, such as deep geological formations.

Solid sorbent direct air capture systems are generally more energy-efficient than liquid solvent systems but require higher temperatures to release the captured CO2. The economic, environmental, and energetic performance of direct air capture processes based on solid sorbents depends significantly on the design and operation of the system. Solid sorbents can be augmented with amine surface functionalization that enhances their interactions with CO2 molecules, thus making them more effective at capturing CO2

Common Types of Solid Sorbents Used in DAC Systems

Solid sorbents are one of the two primary materials used in direct air capture (DAC) systems. Here are some of the most common types of solid sorbents used in direct air capture systems:

1. Solid Alkali Carbonates: Solid alkali carbonates are a type of solid sorbent that can capture CO2 from the air. They are typically used in a fixed-bed reactor, exposed to the air, and selectively absorb CO2.
2. Chemisorbents: Chemisorbents are solid sorbents that react chemically with CO2 to form a stable compound. They are typically made from metal oxides or carbonates and can be used in a fixed-bed or fluidized-bed reactor.
3. Solid-Supported Amine-Based Materials: Solid-supported amine-based materials are adequate for direct air capture due to their high CO2 uptakes and acceptable sorption kinetics. They are typically used in a fixed-bed reactor, exposed to the air, and selectively adsorb CO2.
4. Metal-Organic Frameworks (MOFs): MOFs are a type of porous material that can be used as a solid sorbent for direct air capture. They have a high surface area and can be tailored to selectively adsorb CO2.

The choice of solid sorbent depends on cost, efficiency, and scalability. Researchers need to conduct further studies to optimize the performance and reduce the cost of solid sorbent direct air capture systems, which are still in the early stages of development.

Challenges Associated with Using Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are emerging as promising direct air capture (DAC) technology. They possess exceptional CO2 binding strength and high capacity for CO2 per unit volume. These properties make MOFs an attractive option for DAC applications. However, the utilization of MOFs as solid sorbents for DAC presents several challenges that need to be addressed:

1. Moisture Interference: Moisture in the air poses a significant challenge for MOFs in DAC as it can impede the adsorption of CO2. This interference can diminish the sorbent’s efficiency and hinder its ability to capture CO2 effectively.
2. High Regenerability Costs: Regenerating MOFs can be expensive, contributing to DAC’s overall cost. The release of captured CO2 from MOFs requires high temperatures, which are energy-intensive and can result in significant expenses.
3. Scalability: Although MOFs hold promise for DAC, they are still in the early stages of development. Further research is necessary to optimize their performance and reduce costs. Additionally, scaling up MOFs to industrial levels is challenging, limiting their applicability in large-scale DAC systems.

Despite these challenges, MOFs remain an up-and-coming technology for direct air capture. Ongoing research is dedicated to developing new MOFs with enhanced properties and reducing associated costs to weed out these issues and unlock the full potential of MOFs for DAC.

Key Players in Direct Air Capture

1. Carbon Engineering: It is a Canadian company that has developed a DAC technology that uses a liquid solvent to capture CO2 from the air. The captured CO2 can be used or stored to produce synthetic fuels.
2. Climeworks: Climeworks is a Swiss company that has developed DAC technology that uses solid sorbents to capture CO2 from the air. The captured CO2 can be used for various applications, including greenhouse cultivation and carbonated beverages.
3. Global Thermostat: A US-based company has developed DAC technology that uses solid sorbents to capture CO2 from the air. The captured CO2 can be used for a range of applications, including enhanced oil recovery and the production of building materials.
4. Carbon Clean Solutions: Carbon Clean Solutions is an Indian company that has developed a DAC technology that uses a liquid solvent to capture CO2 from the air. The captured CO2 finds applications in a range of uses, including enhanced oil recovery and the production of building materials.
5. Microsoft: Microsoft is a technology company that has committed to becoming carbon-negative by 2030. The company has invested in several DAC projects, including a partnership with Carbon Engineering to develop a DAC plant in the US.

Operational DAC Plants And Their Capacities

1. There are presently 18 DAC plants operating worldwide, capturing more than 0.01 Mt CO2/year. The active plants capture, on average, 10,000 tons of CO2 per year.
2. Currently, 18 DAC facilities operate in Canada, Europe, and the United States, with a total capture capacity of almost 0.01 Mt CO2/year. The largest plant, commissioned in Iceland in September 2021, captures 4,000 tCO2/year for storage via mineralization.
3. The United States expects to have the largest DAC plant in advanced development operational by mid-2020. This plant will have a capacity of up to 1 MtCO2/year.

Role of DAC in Meeting Paris Agreement Objectives

The Paris Agreement wishes to bring down global warming to levels significantly below 2°C above pre-industrial levels, while striving to keep the temperature increase within 1.5°C. Direct Air Capture (DAC) holds the potential to contribute to the goals set forth by the Paris Agreement in the following ways:

1. Carbon Dioxide Removal: DAC technology can effectively extract carbon dioxide from the atmosphere, playing a crucial role in achieving net-zero emissions and mitigating global warming to levels well below 2°C compared to pre-industrial levels.
2. Supporting Just Transitions: DAC offers a means to balance challenging emissions, including those arising from long-distance transport and heavy industry. By addressing these sources of emissions, DAC contributes to a more equitable and fair transition towards a low-carbon economy. It ensures that the burden of reducing emissions is shared proportionately.
3. Environmental Implications: In the context of climate change mitigation, the environmental implications of the large-scale deployment of DAC must be evaluated. Life cycle assessments can evaluate the environmental trade-offs of DAC technologies, helping ensure they don’t result in problem-shifting.
4. Mobilizing Additional Resources: DAC provides a valuable avenue for mobilizing resources to combat climate change. By offering a means to offset emissions that are difficult to avoid, DAC facilitates the increase in ambition for climate action. This, in turn, supports the transition towards a low-carbon economy by providing additional financial and environmental resources.

Supporting Policies for DAC Deployment

Direct Air Capture (DAC) technology holds great promise for achieving carbon dioxide removal and advancing towards net-zero emissions. To effectively support the deployment of DAC, implementing the following policies is recommended:

1. Incentives and Funding: Governments can offer incentives and financial support to encourage the widespread deployment of DAC technologies. This can take the form of tax credits. Additionally, grants and low-interest loans can help alleviate the high upfront costs associated with DAC implementation.
2. Carbon Pricing: Implementing carbon pricing mechanisms can establish a market for DAC by assigning a value to carbon emissions. Moreover, this economic incentive can encourage companies to invest in DAC technologies, leading to increased adoption and reduced deployment costs over time.
3. Regulatory Support: Governments can facilitate DAC deployment by providing regulatory support. Streamlining the permitting process and establishing clear guidelines can reduce barriers for companies. Additionally, offering regulatory incentives can expedite the implementation of DAC technologies.
4. International Cooperation: Collaboration between nations is crucial for supporting DAC deployment, especially in developing countries. International cooperation can involve financial assistance and technical support to ensure equitable access to DAC technologies, fostering sustainable development worldwide.
5. Research and Development: Governments should prioritize funding research and development initiatives focused on DAC technologies. This support can drive innovation, enhance system efficiency, and reduce deployment costs. Funding for fundamental research, as well as backing for pilot projects and demonstration plants, can accelerate progress in the field.

Market Incentives And Public Investment

Market incentives and public investment can significantly support deploying Direct Air Capture (DAC) technologies. Here are some examples of market incentives and public investment:

1. Government Incentives: Governments can provide incentives to support the deployment of DAC technologies. This can include tax credits, grants, and low-interest loans to help offset the high costs of DAC deployment. For example, the federal 45Q tax credit in the United States has been raised to $180/ton from $50/ton, making DAC projects more financially viable.
2. Public Investment: Public investment can support the deployment of DAC technologies. Funding research and development, pilot projects, and demonstration plants can accomplish this. For example, the US Department of Energy has announced a significant investment in DAC technologies. This includes chemical DAC technologies, biomass carbon removal and storage, ocean-based carbon removal, and enhanced weathering.
3. Private Investment: Private investors can also support the deployment of DAC technologies. Private investment can fund research and development, pilot projects, and demonstration plants. Private investors increasingly support DAC, with Breakthrough Energy Ventures targeting up to $1.5 billion in investment for DAC technologies.

Research Challenges And Opportunities

Research Challenges:

• High Costs: DAC is currently more expensive than other carbon capture technologies, and the cost of DAC needs to be reduced to make it more competitive
• Energy Requirements: DAC requires a significant amount of energy to operate, which can increase the cost and carbon footprint of DAC systems
• Environmental Impacts: The environmental impacts of DAC need to be evaluated to ensure that they do not result in environmental problem-shifting
• Scalability: DAC is still in the early stages of development, and further research is needed to optimize its performance and reduce its cost. DAC is also challenging to scale up to industrial levels, which can limit its use in large-scale DAC systems

Innovation Opportunities:

• Technological Advancements: Technological advancements are needed to reduce the cost and energy requirements of DAC systems. This can include the development of new materials and processes that are more efficient and cost-effective
• Policy Support: Policies such as incentives and funding, carbon pricing, regulatory support, international cooperation, and research and development can support the deployment of DAC technologies and help to achieve carbon dioxide removal and net-zero emissions.
• Collaboration: Collaboration between industry, academia, and government can help to accelerate the development and deployment of DAC technologies. This can include partnerships to develop and test new DAC technologies, as well as collaborations to share knowledge and best practices

Private Investors Supporting DAC

Various programs and initiatives have bolstered direct air capture (DAC) support. For instance, the X-Prize initiative has allocated up to USD 100 million to fund promising carbon removal proposals, including those focused on DAC. Another notable program is Breakthrough Energy’s Catalyst Program. It raises funds to invest in crucial decarbonization technologies, with DAC being one of the areas of interest.

Furthermore, the Lowercarbon Capital Fund made headlines in April 2022 by announcing its intention to invest a substantial sum of USD 350 million in start-ups developing technology-based carbon dioxide removal (CDR) solutions, including DAC.

Moreover, a coalition of prominent businesses formed Frontier Climate, including Stripe, Alphabet, Shopify, Meta, etc. This buyer’s group has committed to utilizing advanced market commitments to purchase an initial USD 925 million worth of permanent carbon removal between 2022 and 2030.

These initiatives and collaborations demonstrate the growing recognition and commitment from various sectors. They also aim to support DAC and advance carbon removal technologies as part of broader efforts to combat climate change.

Cost Of DAC Implementation

The implementing cost of DAC technology varies based on factors such as the chosen technology and deployment scale. The cost range for DAC typically falls between $250 and $600 per tonne of CO2 removed.

To make DAC more competitive and scalable, it is essential to reduce its cost. The Department of Energy initiated the Carbon Negative Shot program in late 2021 to address this. This initiative aims to lower the cost of carbon removal technologies. It also approaches a gigaton-scale deployment of $100 per tonne of CO2 over the next decade. It is expected that supportive policies and market development will reduce the cost of DAC, potentially accelerating the widespread adoption of this technology. Notably, the 45Q federal tax credit in the United States has been increased from $50 to $180 per tonne, enhancing the financial viability of DAC projects.

Conclusion

The Intergovernmental Panel on Climate Change has said that, in the scenarios they assessed, limiting atmospheric warming to the key level of around 1.5 degrees Celsius requires global greenhouse gas emissions to peak by 2025 at the latest. Even with a breakthrough sorbent, the critical factor is integrating the DAC system with low-carbon energy sources. This integration is essential for ensuring the successful and sustainable removal of CO2. Hence, establishing the lifetime of the sorbent, including appropriate operating conditions and stability to CO2 uptake-release cycles. Therefore, there is also the need to develop technology platforms that transfer energy efficiently. Taken together, intensive research focus, government policy and support, and private industry funding are necessary. Overcoming the technological challenges of developing viable DAC systems to operate at a net-zero cost requires these efforts.

To meet net-zero goals, promote diverse DACS (direct air capture and storage) techniques. Include established and innovative methods. Increase chances of success by embracing variety. By scaling up DACS technologies, we can bridge the carbon dioxide removal (CDR) gap. This will also help us make significant progress toward our sustainability targets. Moreover, investing in a diverse range of DACS methods in the coming decade is essential. However, it is likely that the industry may eventually gravitate towards a select few predominant approaches. Additionally, relying solely on a single method poses a substantial risk to DACS. Thus, failing to contribute effectively to CDR is a scenario our planet cannot afford to face.