Is direct air capture (DAC) efficient? This question rightfully dominates discussion around scaling this new climate technology, as one of DAC’s biggest cost drivers and sustainability challenges The short answer is: “it depends” — since direct air capture efficiency is decided by a huge range of variables, from materials used, to energy source, to the location and application of the system.
A direct air capture plant is effectively a finely tuned ecosystem, where every component’s performance is interconnected. A tweak in one area often sends ripples through the entire system, requiring adjustments to keep everything running smoothly. As such, the efficiency of a DAC system is far from static and can vary considerably depending on real-world conditions. That’s why efficiency isn’t about optimising one piece of the puzzle — it’s about taking a holistic approach to ensure that every element works together for maximum impact in any given environment.
Not a simple answer, we know. To help navigate the nuance, we’ve broken down exactly what goes into DAC efficiency, shedding light on the factors that have the most significant impact on performance, and outlining key areas for innovation.
The role of air capture and flow in carbon capture efficiency
Carbon capture efficiency starts at the very beginning of the process, where ambient air is pulled in. There are two key considerations here: airflow rate (how much air is pulled in at any given time), and contact time between that air and the capture medium.
Slowing the airflow through the system can increase the capture percentage of CO2, as it’s exposed to the capture medium for a longer amount of time. Fine tuning the system is key to finding the sweet spot between the volume of air — and therefore CO2 — processed, and the amount of time the air is exposed to the capture medium. In solvent-based systems, increasing air flow requires a corresponding adjustment in liquid solvent flow, demonstrating the knock-on effect of every change targeting improved direct air capture efficiency.
It’s worth noting that the goal here isn’t to capture 100% of the CO2 in the air. After a certain threshold, the closer you get to 100%, the more energy is required, causing a drop in efficiency.
DAC’s energy source and consumption rate
When it comes to direct air capture efficiency, where you source the energy to power the process, and how much of it you use, can have a huge impact.
It might seem natural to assume that the less energy a direct air capture system consumes, the more efficient it will be. However, it’s a little more complicated than that, as minimum energy usage does not, in fact, equal maximum energy (or cost) efficiency. Put another way, running a DAC system at its lowest power consumption doesn’t necessarily get the best value out of it. For example, by increasing energy consumption, it may be possible to tip a system into its optimal, or ‘Goldilocks’, performance zone, meaning more CO2 is removed from the atmosphere per kilowatt hour. Although more energy is required overall, the system is more efficient in its output.
This ability to change DAC’s power consumption is unique to electrified systems. Tapping into this energy flexibility offers a huge advantage for ensuring cost-optimal output against a constantly changing energy profile; whereby you can ramp up energy consumption to recover more CO2 when renewable energy is cheap and abundant, and dialling it down when energy is more expensive or in demand.
That being said, DAC’s technological foundations should allow a system to operate at a reasonable baseline that avoids unnecessary energy consumption in the form of heat or pressure (more on that later). It’s a delicate balancing act, and different direct air capture technologies call for different approaches.
It goes without saying that in order to fulfil its desired outcome, direct air capture should be integrated with a renewable, or low carbon power source. As well as ensuring that the technology is carbon-negative whilst operating, this can also remedy the curtailment of surplus energy that can’t be stored using the grid. One of the many benefits of direct air capture is that thanks to its location flexibility, it can be sited alongside the build-out of renewables.
Chemical performance and direct air capture efficiency
The choice of chemicals used to separate carbon from the atmosphere can also play a crucial role. The sorbents or solvents responsible for capturing CO₂ must effectively bind to the gas whilst remaining durable and capable of multiple regeneration cycles over years of operation, without significant degradation. The need to frequently replace materials can increase operational costs and resource consumption, reducing long-term efficiency. Designing materials with high longevity ensures consistent performance, with the added bonus of a lower environmental footprint thanks to reduced material production and disposal needs.
The impact of DAC’s operating environment
DAC can be located almost anywhere in the world, meaning the technology has to adapt to a wide range of local variations in operating environment — all of which impact overall system efficiency. Temperature variations, seasonal changes, and humidity levels all affect performance.
System efficiency can fluctuate with seasonal temperature changes. For example, lower temperatures may slow chemical reactions, while higher temperatures can enhance certain processes, but may require additional cooling mechanisms and impact the longevity of the system.
In liquid-based DAC systems, water loss can be a concern in hot and arid environments. High humidity can impact a sorbent's ability to release CO₂ efficiently, requiring additional regeneration efforts. Conversely, very dry air can reduce sorbent performance and increase system wear.
Direct air capture system design, procurement, and engineering
The design and engineering of a DAC system influences efficiency at every stage, from daily operations to long-term scalability. A well-designed system requires minimal maintenance and input during operation, reducing downtime and ensuring steady performance. Scalability is another crucial factor — future-proof DAC should be designed for system expansion without the need for a complete infrastructure overhaul. Early investment in the form of capital expenditure can reduce the long-term cost of direct air capture by bringing down operational spending.
Learn more: Direct air capture price explained: Breaking down the cost of atmospheric CO2.
Supply chain, perhaps surprisingly, also plays a role. It’s important to consider how system components are sourced to be able to accurately assess the efficiency of the process as a whole. Designing systems with widely available materials and easily replaceable parts streamlines production, reduces costs, and ensures reliability. It’s precisely why we’re purposely using proven technology to scale direct air capture quickly and efficiently.
CO₂ utilisation vs. CO₂ storage
Once CO₂ is recovered, its intended use determines system design and efficiency requirements. Some DAC systems are designed for permanent storage via geological sequestration, requiring high-purity CO₂ and a reliable transport system. Others prioritise utilisation pathways, where atmospheric CO₂ is used as a sustainable carbon resource to defossilise carbon-based products like fuels and building materials.
Different DAC approaches vary in how they capture, transport, and release CO₂, which influences the energy required and the purity of the resulting CO₂ stream. High-purity CO₂ can be achieved in both liquid- and solid-based systems, but it often depends on the specific separation method used. For example, DAC systems that incorporate membrane-based separation—where CO₂ is transported across a gas-impermeable membrane—can inherently deliver high-purity streams. In contrast, processes like thermal desorption from solid sorbents or calcination reactions may result in trace levels of oxygen and nitrogen in the product gas, requiring additional purification. Striking the right balance between capture rate, energy input, and output purity is essential to optimise DAC systems for their intended end use, whether that’s permanent storage or commercial integration.
How to increase direct air capture efficiency
Maximising direct air capture efficiency translates to more than just cutting energy use — it’s about finding equilibrium within the system.
- From energy sourcing and system design to material longevity and airflow optimisation, each of these elements play a role in determining overall performance.
- DAC systems must be designed to minimise unnecessary energy losses, align with renewable or low carbon power sources, and adapt to environmental conditions.
- Energy flexibility should be leveraged to reach a minimised levelised cost (capital expenditure plus operating expenses).
- By continuing to refine these processes through a holistic, whole-system approach, we can drive DAC towards greater affordability, scalability, and effectiveness in the fight against climate change.
