DAC has always promised a seductive narrative: the ability to suck carbon out of the sky, store it underground, and buy ourselves a climate mulligan. It promised to clean up after fossil fuels without requiring too many lifestyle changes. It was a technology that said yes — to oil companies, to airlines, to governments slow-walking their emissions policies. And for a time, it looked like it might work. Big names like Microsoft, Stripe, and Shopify lined up to buy carbon removal credits at $600 a ton or more. Government agencies began pouring in cash. The US 45Q tax credit was sweetened to $180 per ton. Europe and Japan set aside funds. And dozens of startups bloomed. But beneath the marketing sheen, the physics was never on DAC’s side.

Removing CO₂ from ambient air is a thermodynamic slog. The concentration is a measly 0.04% — less than one molecule in 2,500. Capturing it means moving vast volumes of air across chemically active surfaces, then applying heat, vacuum, or electric fields to regenerate the sorbents. The most mature systems, like Climeworks’ solid sorbent modules or Carbon Engineering’s hydroxide-calcination loop, require on the order of 2,000 to 3,000 kilowatt-hours of energy per ton of CO₂. Even newer concepts that promise electrochemical capture still hover around 700 to 1,000 kWh per ton. And that’s just to capture it. Compressing, transporting, and injecting it underground adds another layer of complexity and cost. Back in 2019, I analyzed Carbon Engineering’s system in detail and concluded that it wasn’t ready for prime time. The energy requirements were steep, the system architecture was complex, and the economic case relied heavily on theoretical scale and generous subsidies. Fast forward to today, and those conclusions still hold. Carbon Engineering’s Squamish pilot captured a few hundred tons over several years. Its first commercial plant, Stratos in Texas, is still under construction. Occidental Petroleum acquired the company in 2023 not because it had a viable climate solution, but because it had a narrative that could buy time for oil and gas. Stratos, too, will run on natural gas. The captured CO₂ will be injected underground and earn 45Q credits, while Occidental continues to sell hydrocarbons. This isn’t carbon removal. It’s corporate theater wrapped in a green ribbon.

Both Climeworks and Carbon Engineering rely on energy-intensive processes that significantly affect their net CO₂ removal performance. Climeworks uses solid amine sorbents that require low-grade heat, typically around 80–100 °C, to regenerate. While its Icelandic operations claim to run on geothermal heat and renewables, life-cycle analyses show that even with clean power, the system still re-emits about 10% of the CO₂ it captures — due to embedded emissions in materials, equipment fabrication, and operational energy overhead. When fossil-derived heat or grid power is used, the carbon intensity increases sharply.

Carbon Engineering’s system is even more demanding, using around 8.8 GJ of thermal energy and over 360 kWh of electricity per ton of CO₂ removed. In its commercial configuration, it burns natural gas to provide high-temperature heat for calcination, capturing the resulting CO₂ from combustion alongside that from the air. While this design recovers some of the emissions, the system still emits roughly 0.1–0.2 tons of CO₂ for every ton it captures — less if powered by renewables, more if grid electricity or inefficient fuel use is involved. In both cases, without access to extremely low-carbon energy, the DAC process risks becoming a net emitter or offering only marginal removal at best. That low-carbon energy is much better used to power electric cars or heat pumps to avoid more CO2 being emitted in the first place, rather than used to extract homeopathic amounts of CO2 from the air.

Direct air capture, like the broader class of carbon capture and storage (CCS) projects, has been used less as a mitigation tool and more as a justification tool. Capture projects at the smokestack were supposed to save coal. They didn’t. DAC was supposed to save aviation. It isn’t. Now it’s being positioned as the backstop for net-zero oil and gas production, a way to square the carbon ledger while the meter keeps running. The problem is that the math never adds up. To remove even one gigaton of CO₂ annually — the lower end of what IPCC pathways suggest we might need by mid-century — we would need thousands of DAC plants the size of the one Climeworks can’t get to work. That would require hundreds of terawatt-hours of energy annually, roughly equivalent to doubling the electricity use of a mid-sized industrial nation.....read on https://cleantechnica.com/2025/05/15/climeworks-dac-fiscal-collapse-the-brutal-reality-of-pulling-carbon-from-the-sky/?utm_source=substack&utm_medium=email