Pros and cons of direct air capture (DAC)

While carbon reduction methods are key to reducing carbon emissions, carbon removal of carbon dioxide already present in the atmosphere is even more crucial. One of the emerging technologies in this area is Direct Air Capture (DAC). This works by removing carbon dioxide directly from the air. 

What is Direct Air Capture?

While carbon reduction strategies focus on minimising future emissions, carbon removal technologies like Direct Air Capture (DAC) are essential for addressing existing CO₂ in the atmosphere. DAC works by directly capturing carbon dioxide from the air, using a three-step process:

1. CO₂ capture:

Airborne carbon dioxide is detected and extracted using specialised chemicals.

2. Chemical absorption:

Aqueous alkaline solvents or sorbents react with CO₂, trapping it and allowing heat to regenerate the chemicals for reuse.

3. Storage and sequestration:

The captured carbon dioxide is securely stored, often underground, ensuring long-term removal. 

Advantages of Direct Air Capture

1. Effective carbon removal for net-zero goals

DAC enables industries to reach net-zero carbon emissions by removing existing atmospheric CO₂. For companies unable to eliminate all emissions through operational changes, DAC provides a viable solution for offsetting residual emissions.

2. Carbon utilisation potential in key industries

DAC offers opportunities for carbon utilisation in sectors such as energy and manufacturing. By integrating DAC systems with existing monitoring platforms, these industries can track carbon removal in real-time, aiding in carbon footprint modelling and reduction.

Disadvantages of Direct Air Capture

1. High energy consumption and emissions

DAC requires significant energy input due to the high temperatures necessary for chemical reactions. For instance, solvent-based systems may need temperatures up to 900°C, leading to substantial energy demand and associated emissions.

2. High costs

The operational and upfront costs of DAC remain prohibitive. Despite potential cost reductions through scaling, DAC currently represents one of the most expensive methods of atmospheric carbon removal.

3. Limited scalability and technological maturity

DAC faces scalability issues due to land requirements and the limited maturity of the technology. Large-scale deployment could compete with agricultural land use, while further research and development are necessary to enhance efficiency and reduce costs.

Applications and case studies for Direct Air Capture

1. Leading DAC projects: Deep sky in Canada

One notable project is Deep Sky, a Canadian initiative aimed at advancing DAC technology. Launched in December 2024, it expects to capture 3,000 tonnes of CO₂ annually, with a goal of 30,000 tonnes per year by 2034.

• Location: Alberta, Canada

• Method: Geological sequestration

• Companies Involved: Skytree, Airhive, Avnos, Phlair, Greenlyte Carbon Technologies, Mission Zero, NEG8 Carbon, Skyrenu

DAC developers from Europe, such as Skytree, have partnered with Deep Sky to deploy DAC units powered by Alberta’s renewable hydroelectric energy.

2. DAC integration in other industries

DAC technology is finding applications beyond energy, particularly in:

• Agriculture: Creating climate-neutral animal feedstock

• Transportation: Producing synthetic aviation fuels

• Food and Beverage: Providing CO₂ for carbonated drinks

Future of Direct Air Capture technology

Innovations are underway to overcome DAC’s current limitations. Companies like Climeworks are leading the charge by using geological storage with minimal land and water usage. Additionally, policy support and emerging market opportunities are encouraging DAC scaling.

Technological advancements include:

• Low-temperature heat treatments to reduce energy consumption

• Modular plant designs for flexible deployment in various locations

Compared to traditional carbon capture and storage (CCS), which only captures emissions at the source, DAC offers a broader solution by removing already-released atmospheric CO₂. As innovations continue, DAC could play a pivotal role in global carbon reduction strategies.

While DAC holds immense potential for carbon removal and utilisation, it faces challenges like high costs and energy demands. Continued innovation and policy support will be crucial for scaling this promising technology.