What are the biggest scientific uncertainties around direct air capture?

How much will DAC actually cost, and how much energy will it need?

The single biggest uncertainty is cost. Current DAC systems cost between $300 and $1,000 per ton of CO₂ captured [10], which is 2–6 times higher than the $100/ton target needed for widespread economic viability [2]. Even optimistic projections for large-scale deployment (1 billion tons per year cumulative capacity) put costs at $226–$544 per ton for liquid solvent systems, $281–$579 for solid sorbent systems, and $230–$835 for a newer weathering-based approach [4] — all well above $100.

Energy demand is another huge unknown. DAC requires 1,500–2,400 kWh of energy per ton of CO₂ captured [10], and the source of that energy dramatically affects both cost and net climate benefit. If the energy comes from fossil fuels, the process may not even be carbon-negative. Offshore DAC, which could tap abundant renewable energy, faces additional energy penalties: removing salt from marine air before capture could increase fan energy requirements by 38–194 kWh per ton depending on the technology [1].

These cost and energy figures come with wide confidence intervals because DAC is still a pre-commercial technology. The projections in [4] are probabilistic, meaning they reflect a range of possible outcomes, not a single prediction. The bottom line: no one knows yet whether DAC can reach the cost and efficiency targets needed for large-scale deployment.

Which materials and processes will work best at scale?

There is no consensus on the best capture material or process. Solid sorbents like metal-organic frameworks (MOFs) and amine-functionalized polymers show promise but face major hurdles: water in the air can interfere with capture, and the materials can degrade over time [10]. Liquid solvents using amino acid salts, such as potassium glycinate, have shown stable performance in lab tests but need further validation [5]. Electrochemical and membrane-based approaches are even less mature and face issues like oxygen sensitivity and poor selectivity [9].

A key uncertainty is how these materials behave in real-world conditions. Most lab studies use idealized dry air, but real air contains water vapor, pollutants, and — in coastal or offshore settings — salt particles that can poison sorbents [1]. The Open DAC 2023 dataset [7] highlights that previous computer screening of MOFs ignored water adsorption and material deformation, which quantum chemistry calculations show are critical. This means many promising materials identified in silico may fail in practice.

The diversity of approaches — from solid sorbents to liquid solvents to electrochemical cells — is itself a sign of uncertainty. No single technology has emerged as clearly superior, and the field is still in the 'let's try everything' phase [8][10].

Can DAC scale to billions of tons per year, and who will pay for it?

Scaling DAC to climate-relevant levels (billions of tons per year) faces deep uncertainty. One modeling study found that while DAC could become the most deployed carbon removal technology by 2100 — a median of 6.7 billion tons per year — the range of possible outcomes is enormous (4 to 8.7 billion tons per year), depending largely on future renewable energy capacity and geological storage injection rates [6]. Another study using global sensitivity analysis found that DAC deployment has a 'fat-tailed' distribution: most scenarios show modest uptake, but there is a small (4–6%) chance of reaching gigaton scale by mid-century [3].

The policy and financial requirements are staggering. To reach gigaton scale, subsidies would need to exceed $200–330 per ton of CO₂ and be sustained for decades, totaling $900–$3,000 billion in public support [3]. Even then, the investment only pays off if accompanied by strong emission reduction policies. Current global DAC capacity is only about 0.01 million tons per year [2] — a factor of 100,000 short of what might be needed.

Location also matters enormously. DAC plants need access to low-carbon energy, CO₂ storage or utilization sites, and favorable climatic conditions [9]. Offshore locations offer proximity to wind/solar and storage but add engineering complexity and cost [1]. The interplay of these factors means that the 'best' DAC strategy will vary by region, and no single deployment pathway is clearly optimal.

About These Sources

This answer is built on 10 peer-reviewed studies — published from 2022 to 2026, 8 from 2024 or later, 6 in Q1 journals, collectively cited 613 times — selected as the most relevant from 11 studies that passed quality screening, drawn from 64 papers retrieved from a database of over 500 million.

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