Sky-High Carbon Removal Showdown: Climeworks Gen 2 vs. Heirloom Limestone vs. Carbon Engineering’s AIR2 DAC

Direct air capture (DAC) has emerged as a bold technology to suck CO₂ from the sky and help reverse climate change. In 2025, three frontrunners – Climeworks, Heirloom, and Carbon Engineering – are racing to scale DAC with very different approaches. Each company’s system has unique technical designs, energy needs, costs, and partners shaping its path. This report provides an in-depth comparison of Climeworks’ Generation 2 modular DAC system, Heirloom’s limestone-based DAC process, and Carbon Engineering’s AIR2 contactor (large-scale air contactor). We’ll dissect how they capture CO₂, their efficiency and energy requirements, how easily they scale up, land and material needs, cost per ton, deployment status, business models, and what’s coming next.

Why these three? Climeworks of Switzerland opened the world’s first commercial DAC plant and champions a modular, solid-sorbent design. Heirloom, a U.S. startup, uses the natural power of limestone to capture CO₂, claiming a low-cost path by accelerating mineralization heirloomcarbon.com heirloomcarbon.com. Canada’s Carbon Engineering (now part of Occidental Petroleum) pioneered a liquid-solvent DAC system and is behind some of the largest planned CO₂ removal projects spectrum.ieee.org oxy.com. All have attracted major investments and customers (from Big Tech to big oil) betting on DAC as a climate solution.

Table 1 – At a Glance: Comparing Climeworks, Heirloom & Carbon Engineering

Table 1: Side-by-side comparison of Climeworks, Heirloom, and Carbon Engineering’s DAC approaches on key metrics. Sources: Climeworks Gen2/3 data canarymedia.com latitudemedia.com, Mammoth capacity climeworks.com, Heirloom process and energy heirloomcarbon.com latitudemedia.com, Carbon Engineering process and energy spectrum.ieee.org energymixweekender.substack.com, cost and policy estimates canarymedia.com latitudemedia.com, deployment timelines climeworks.com heirloomcarbon.com oxy.com, and company announcements.

Climeworks: Modular DAC with Solid Sorbents (Generation 2 → 3)

Climeworks, founded in 2009 in Switzerland, has led the DAC field with its modular carbon collector units. In Generation 2, each unit is a boxy container housing a fan and sorbent filters. Air is drawn in, and CO₂ chemically binds to the filter’s amine-based material; once the filter is saturated, the unit closes and heats the sorbent to ~100 °C, releasing concentrated CO₂ gas for capture spectrum.ieee.org spectrum.ieee.org. The CO₂ is then pumped underground and mineralized into rock (in Iceland’s basalt formations via Carbfix) for permanent storage spectrum.ieee.org. This cyclic process can run multiple times a day per module. Notably, Climeworks’ system runs entirely on renewable energy (waste heat or green electricity) to avoid re-emitting the CO₂ it worked to capture latitudemedia.com.

Gen 2 Performance: Climeworks’ Gen2 plants have proven the concept but at relatively small scales so far. Its Orca plant in Iceland (online since 2021) has a nameplate capacity of 4,000 tons CO₂ per year (8 modules) latitudemedia.com – at the time, the largest DAC plant in the world. A follow-up, Mammoth, is designed for 36,000 t/yr (72 modules) – an order of magnitude bigger climeworks.com. Mammoth broke ground in mid-2022, and by May 2024 Climeworks had “90% of the systems operational” on site climeworks.com. However, only 12 of 72 collector containers were initially installed and running as of early 2025, due to technical hiccups with the new filter design latitudemedia.com latitudemedia.com. Those first modules underperformed – plant manager Maxim Willemse noted the Gen2 filters were “failing earlier than expected” in real-world conditions latitudemedia.com. Rather than replicate the flaw 72 times, Climeworks paused installation to troubleshoot and apply fixes latitudemedia.com latitudemedia.com. This cautious approach means Mammoth captured only ~100 tons in its first months (a tiny sliver of its potential) latitudemedia.com, but it underscores Climeworks’ learning-curve mentality. “We have some difficulties that need to be remedied… It doesn’t make sense to put all those other containers out there and see them fail in the same way,” Willemse explained latitudemedia.com. By iterating quickly, the company aims to de-risk the technology at each scale step latitudemedia.com latitudemedia.com.

Gen 3 Breakthrough: In 2024, Climeworks unveiled its Generation 3 DAC technology, calling it “a major milestone” for cost and efficiency canarymedia.com. After five years of R&D and a testing campaign in Switzerland, Gen3 is reported to capture twice as much CO₂ per module as Gen2, while using 50% less energy, and at half the cost per ton canarymedia.com. “Generation 3 is what matters as we move ahead… that is going to be the basis of how we scale,” said Climeworks COO Douglas Chan canarymedia.com. The Gen3 units use a completely redesigned sorbent configuration: laminated sorbent sheets with embedded chemical adsorbent, as opposed to the loose sorbent beads packed in Gen2 cartridges latitudemedia.com. This increases the contact surface with air and reduces air flow resistance. The improvements should sharply reduce the energy needed per ton (currently Climeworks has been around the higher end of industry energy use, perhaps on the order of 6–8 GJ/t including heat latitudemedia.com, though exact figures aren’t public). Indeed, with Gen3, Climeworks expects to cut its ~$1000/ton cost today down to the $250–$350/ton range by 2030 canarymedia.com, bringing DAC closer to viability canarymedia.com. The first deployment of Gen3 modules will be at the Project Cypress megaton-scale DAC hub in Louisiana (U.S.), scheduled for 2029 canarymedia.com. That plant – supported by a $600 million U.S. DOE grant – aims to remove 1,000,000 tons/year of CO₂, which would make it the largest DAC endeavor globally canarymedia.com. Dozens of Gen3 modules will be clustered there (Climeworks released concept art showing an array of cube-like units on the Gulf Coast) canarymedia.com canarymedia.com.

Scalability and Vision: Climeworks has always championed modularity for scaling. “Our carbon collectors can be stacked to build facilities of any size,” notes co-CEO Jan Wurzbacher spectrum.ieee.org. This LEGGO-like approach, combined with aggressive scale-up of project size, is how Climeworks plans to reach climate-relevant volumes. “Based on the most successful scale-up curves, reaching gigaton by 2050 means delivering at megaton scale by 2030,” co-founder Christoph Gebald said – “Nobody ever built what we are building in DAC… the most certain way to be successful is to run the technology in the real world as fast as possible and relentlessly deploy it.” climeworks.com This sums up Climeworks’ strategy: learn by doing, even if that means some modules underperform at first, and keep 10× scaling the plant sizes. Orca to Mammoth was a 10× jump (0.004 Mt to 0.036 Mt). The next leap to Cypress is ~30× (1 Mt), and Climeworks hopes to replicate megaton DAC plants worldwide thereafter, riding down the cost curve. They are exploring projects in various regions – from Oman (with partner 44.01 for underground mineralization) climeworks.com to other U.S. locations and Europe – wherever low-carbon energy and CO₂ storage are available. By 2050, the vision is to deploy enough modular plants to remove gigatons of CO₂ per year climeworks.com climeworks.com, making a meaningful dent in global emissions.

In summary, Climeworks’ Gen2/Gen3 DAC stands out for its plug-and-play design and use of solid sorbents. Its strengths include relatively low-temperature regeneration (making it easier to power with abundant heat sources) and a small footprint, as well as being fully operational today (proving permanent CO₂ storage via Carbfix). The challenges remain lowering costs (from ~$600+ per ton down toward the $100/ton goal) and improving the longevity and performance of sorbent modules. With a huge war chest of funding and high-profile customers, Climeworks is pushing the envelope – and if Gen3 delivers as claimed, it could halve the brutal energy and cost requirements that have plagued DAC canarymedia.com. As Chan put it, Gen3 is the platform on which Climeworks plans to “continue to scale throughout the industry” canarymedia.com, aiming to maintain its pole position in the carbon removal race.

Heirloom: Accelerating the Limestone Cycle for Low-Cost DAC

California-based Heirloom takes a very different tack – one that blends engineering with geology. Rather than synthetic chemicals, Heirloom’s system harnesses limestone, one of Earth’s most abundant minerals, to capture CO₂. It essentially turbocharges the natural carbonatation cycle that would ordinarily take years or decades, shrinking it to days heirloomcarbon.com heirloomcarbon.com. The process is often described as “growing rocks with wind”, because CO₂ from the air is literally turned into stone (calcium carbonate) as the removal mechanism latitudemedia.com.

How it Works: The cycle has three main steps:

1. Calcination (CO₂ Release): Limestone (CaCO₃ rock) is heated in a kiln to ~900 °C, causing it to decompose into calcium oxide (CaO) and pure CO₂ gas heirloomcarbon.com. The CO₂ is captured and will later be permanently stored (in Heirloom’s pilot, it’s injected into concrete via CarbonCure latitudemedia.com; future plants will inject CO₂ underground via partners like CapturePoint heirloomcarbon.com). The leftover CaO is a powdery quicklime.
2. Recarbonation (CO₂ Capture): The CaO is mixed with a bit of water (forming calcium hydroxide, Ca(OH)₂) and spread in thin layers on large trays exposed to the ambient air heirloomcarbon.com. Over the next 3 days or so, the material “pulls CO₂ from the air like a sponge” – the CaO/Ca(OH)₂ reacts with atmospheric CO₂, turning back into solid CaCO₃ (limestone) heirloomcarbon.com latitudemedia.com. Fans can be used to blow air over the trays when wind is insufficient latitudemedia.com, ensuring a steady supply of CO₂. The process is exothermic (it gives off a bit of heat as the CO₂ binds to the mineral) and requires no added energy during the absorption phase.
3. Looping: Once the material is saturated as CaCO₃, the trays are collected by robots and the “recharged” limestone goes back into the kiln latitudemedia.com. Heating releases the CO₂ (which is captured for storage) and regenerates CaO, which can be laid out on trays again. The cycle then repeats many times with the same material.

Heirloom essentially created an industrial-strength weathering loop. Nature would take perhaps a year for limestone pebbles to passively absorb significant CO₂; Heirloom does it in days by maximizing surface area (powder on trays) and controlling conditions heirloomcarbon.com. The company’s secret sauce includes algorithmic modeling and automation – their tray fields are tended by AI-driven robots that monitor the reaction progress and shuttle trays at just the right time latitudemedia.com. “We modeled the chemical reaction algorithmically,” explains Heirloom’s Chief Commercial Officer, and a fleet of robotic “rock babysitters” move up and down the 40‑ft stacks to swap out trays as soon as they’re saturated latitudemedia.com. This high-tech choreography minimizes downtime and optimizes each cycle’s CO₂ uptake.

Energy and Efficiency: Unlike Climeworks or Carbon Eng, Heirloom does not require large continuous fans or blowers for its core capture (natural airflow does a lot of the work, supplemented by fans only when needed). This saves electricity. The energy-intensive step is the kiln, which must heat limestone to 900 °C to kick CO₂ out of the rock. Heirloom has committed to using 100% renewable energy for this step – in practice, that means electric resistance or induction heating in the kiln, or other zero-carbon heat sources heirloomcarbon.com heirloomcarbon.com. (They partnered with Leilac, which developed an efficient electric kiln for the cement industry, to deploy this technology in future plants heirloomcarbon.com.) Current pilots likely use an electric kiln powered by California’s grid or solar. The total energy per ton of CO₂ removed is around 2,500 kWh/ton (per Heirloom’s reports) latitudemedia.com. To break that down: the calcination reaction itself is thermochemically demanding (~1790 kWh/ton CO₂ theoretically), plus heat losses and some electricity for handling, giving ~2,500 kWh. They are targeting <2,000 kWh/t with optimizations latitudemedia.com – notably Leilac’s kiln tech can improve heat transfer and reduce losses. For context, this is in the same ballpark as Climeworks’ solid-sorbent approach and somewhat lower than Carbon Engineering’s solvent process (which is ~2,800 kWh/t including gas consumption) latitudemedia.com. One reason is that Heirloom doesn’t require additional energy for sorbent regeneration beyond calcination – the CaO is the sorbent and is regenerated inherently by the heating step that also releases CO₂.

The chemistry efficiency is high: each cycle, nearly all the CaO is converted back to CaCO₃, capturing a mass of CO₂ almost equal to the starting rock (1 ton of CaO can capture ~0.79 tons CO₂). There may be some attrition or incomplete carbonation, but makeup limestone is cheap and plentiful. A small amount of fresh limestone can be added periodically to replace any deactivated material. All inputs (rock, water, power) are readily available, which gives this approach a potential cost edge. “By using easy-to-source materials like limestone… Heirloom’s technology represents one of the lowest cost pathways to permanent CO₂ removal,” the company claims heirloomcarbon.com. Indeed, limestone costs on the order of $10–20 per ton (negligible per ton of CO₂ captured), compared to expensive proprietary sorbents or solvents that other DAC methods need.

Current Status and Scale-Up: Heirloom was founded in 2020, making it remarkably young. Yet by late 2023 it had already built North America’s first commercial DAC facility – a small plant in Tracy, California that can capture 1,000 tons of CO₂ per year heirloomcarbon.com. U.S. Energy Secretary Jennifer Granholm, at the launch event, lauded it as “the closest thing on Earth we have to a time machine, because it can turn back the clock on climate change” by removing already-emitted CO₂ heirloomcarbon.com. That facility, fully powered by a local solar farm, has been running since mid-2023 and is delivering CO₂ to be stored in concrete via CarbonCure heirloomcarbon.com. It employs a modular array of tray stacks and a kiln on site – and notably, it’s almost entirely automated, with minimal human intervention day-to-day latitudemedia.com.

From 1,000 tons, Heirloom is now leaping to much larger projects:

• In Shreveport, Louisiana, Heirloom will construct two DAC facilities at the Port of Caddo-Bossier. The first, starting construction in 2024, will capture 17,000 t/yr and begin operation in 2026 heirloomcarbon.com heirloomcarbon.com. The second is part of the DOE-backed Project Cypress DAC Hub and is slated for 100,000 t/yr by 2027 (Phase 1), expanding to 300,000 t/yr with subsequent phases heirloomcarbon.com heirloomcarbon.com. Combined, that’s ~320,000 t/yr by late 2020s – a huge scale-up, making Heirloom one of the largest players by capacity if achieved heirloomcarbon.com heirloomcarbon.com. Louisiana is attractive for its geology (CO₂ can be stored underground in saline aquifers) and policy support. Heirloom’s hub project won up to $600 million in DOE funding – which significantly de-risks the financing heirloomcarbon.com. The state is also providing incentives and touting the job creation (~1,000 construction jobs, 80+ permanent) heirloomcarbon.com heirloomcarbon.com.
• Heirloom has inked deals with major corporate buyers to secure revenue for these projects. In 2023, Microsoft agreed to purchase up to 315,000 tons of CO₂ removal from Heirloom over 10 years heirloomcarbon.com – one of the largest CDR offtake agreements ever, signaling strong confidence in Heirloom’s tech. Stripe’s Frontier Fund and other buyers similarly signed a $26.6 million agreement for 9,000+ tons (and options for more) from Heirloom’s future facilities frontierclimate.com. Buyers also include Shopify, JPMorgan, Meta, Klarna, and more heirloomcarbon.com heirloomcarbon.com. This “advance market commitment” model (firms paying now for carbon removal delivered later) has been crucial for Heirloom to scale.

Cost Trajectory: Today’s costs for Heirloom are likely in the high hundreds of dollars per ton (as with any DAC). But Heirloom’s CEO Shashank Samala is optimistic about cost reduction. “The capacity of our limestone-based tech has gone from 1 kg of CO₂ to 1000 tons in just over two years,” he noted in 2023 – implying rapid progress – “We owe it to every climate-vulnerable citizen to continue to deploy at the urgent pace required to reach billion-ton scale.” heirloomcarbon.com. By end of this decade (2030), Heirloom anticipates about $300/ton removal cost and to be profitable at that point latitudemedia.com latitudemedia.com. They acknowledge DOE’s stretch goal of $100/ton and aim to push costs down further long-term with technology improvements and scale economies latitudemedia.com. Key levers include the switch to electric kilns (which, with cheap renewable power, could cut operating cost significantly versus any fossil-fueled kiln) and continued refinement of the carbonation process to shorten cycle times or increase throughput per cycle.

Advantages & Challenges: Heirloom’s approach has some clear advantages:

• Low sorbent cost: using cheap, abundant limestone instead of costly manufactured sorbents or solvents heirloomcarbon.com.
• Long-lived sorbent: CaO/CaCO₃ can be reused almost indefinitely (no significant degradation for many cycles, unlike amines which can degrade) – lowering ongoing costs.
• No carbon-intensive inputs: limestone does release CO₂ when calcined, but that CO₂ is exactly what gets captured – it’s part of the closed loop. And using renewable electricity means minimal new emissions. There’s no need for mining new minerals beyond sourcing limestone itself (which is widely available).
• Modularity and siting: tray stacks and kilns can be built in standard industrial areas. The footprint scales with capacity but is not prohibitive. And it can operate anywhere – though efficiency is higher in dry climates (too much humidity can slow carbonation).
• Policy alignment: Heirloom’s focus on permanent storage (and explicit stance of no EOR) aligns with buyers who want high-quality, non-offsetting removals. This made them a darling of climate-conscious investors and tech firms.

Some challenges:

• High heat requirement: 900 °C electric kilns are still relatively novel and can be capital-intensive. Ensuring the kilns run on truly clean power (and cheaply) is essential for climate benefit and economics. The partnership with Leilac is intended to solve this, but scaling electric kilns to hundreds of thousands of tons is a big engineering task.
• Process throughput: The passive CO₂ uptake on trays, even if only 3 days, means a large volume of material has to be in process at any time. For example, a 100,000 t/yr removal plant might need on the order of 300,000 tons of CaO circulating (assuming each cycle captures ~0.33 tons per ton CaO per day, for simplicity). That’s a lot of material handling, and keeping the automation smooth at scale will be a challenge. The robotics and scheduling algorithms will be critical to prevent bottlenecks.
• Water use: Slaking lime uses water. The process emits that water as steam when Ca(OH)₂ converts to CaCO₃, so it may be largely recoverable (and Louisiana’s humid climate might actually help with passive moisture). Still, water management is a factor, though not a dealbreaker.
• Speed of scale: Heirloom is attempting one of the fastest scale-ups in clean tech: from lab in 2020, to 1kt in 2023, to 300kt by ~2028. Execution risks are non-trivial. As carbon removal expert Julio Friedmann quipped, “They [Heirloom] will be overtaken, and soon,” noting that significantly larger projects (like Oxy’s) are coming down the pike latitudemedia.com. In other words, being first to a milestone is great, but maintaining a lead requires consistent expansion.

So far, Heirloom has met its milestones. It delivered the first DAC credits from U.S. soil and earned praise for its “high-road” approach (union labor construction, community engagement, and no fossil fuel entanglements) heirloomcarbon.com heirloomcarbon.com. With strong backing (including top-tier venture funds and even the Governor of California touting it as a model for climate tech heirloomcarbon.com), Heirloom is well-positioned. The next few years – building the Louisiana plants – will test whether its limestone magic can economically rival other DAC methods at large scale. If it succeeds, DAC could indeed become much more affordable. As Secretary Granholm put it: “Projects like this Heirloom facility are exactly the sort of big and innovative ideas we’re embracing – using renewable energy to directly remove pollution from our air, all while creating good-paying jobs.” heirloomcarbon.com In short, Heirloom’s limestone DAC promises a compelling combination: nature’s simplicity with cutting-edge automation, aiming to deliver carbon removal at fossil-fuel scales but without fossil fuels.

Carbon Engineering: Industrial-Scale Liquid Solvent DAC (“AIR2” Contactor Systems)

Carbon Engineering (CE) is the veteran of the group – founded in 2009 and based in British Columbia, it has spent over a decade refining a liquid solvent DAC process that operates on a grand scale. In 2023, Carbon Engineering was acquired by Occidental Petroleum’s 1PointFive subsidiary carboncredits.com, turbocharging its push to commercial deployment. CE’s design is often seen as the most “industrial” approach: it borrows hardware from cooling towers, chemical plants, and pulp mills to create an air-capture refinery for CO₂.

How it Works: Carbon Engineering’s DAC involves two linked chemical loops:

1. In the air contactor, a strong potassium hydroxide (KOH) solution is rained down a structured packing while giant fans pull ambient air up through it spectrum.ieee.org. CO₂ in the air readily reacts with KOH, forming potassium carbonate (K₂CO₃) in solution. The air coming out has most of its CO₂ scrubbed (typically 75%+ removed in one pass) spectrum.ieee.org. The contactor is essentially a wall of corrugated PVC wet with KOH, constantly refreshed, maximizing contact with air carbonengineering.com. Because the CO₂ in air is only ~0.04%, huge volumes of air must be processed – CE’s design uses banks of fans ~8.5 m in diameter each spectrum.ieee.org, with many contactor modules lined up.
2. The CO₂-laden KOH solution is then put through a series of chemical reactions to concentrate and release the CO₂:
   • Calcium cycle: CE adds calcium hydroxide (slaked lime, Ca(OH)₂) to the K₂CO₃ solution in a “pellet reactor.” This precipitates calcium carbonate (CaCO₃) pellets and regenerates KOH (which is recycled to the air contactor) spectrum.ieee.org. The CaCO₃ pellets contain essentially all the CO₂ that was captured from the air.
   • Calciner: The CaCO₃ pellets are fed into a high-temperature calciner (around 900 °C), where they’re heated (by burning natural gas with pure oxygen, in CE’s original design) to release CO₂ gas and leave behind CaO (quicklime) spectrum.ieee.org. The CO₂ is now a pure stream, ready for compression and storage. The CaO is slaked with water to regenerate Ca(OH)₂, which is fed back to the pellet reactor, closing that loop. The calciner’s flue gas (from burning fuel) is also rich in CO₂ and is processed so that its CO₂ is captured too (often by feeding it through the same pellet reactor) – this way, any CO₂ from the fuel doesn’t leak to the air, preserving net removal oxy.com.

In essence, CE’s system concentrates CO₂ via chemical work: air CO₂ → KOH solution → CaCO₃ solid → CO₂ gas. It produces a pipeline-ready stream of CO₂ (typically ~99.5% purity). The choice of KOH and Ca(OH)₂ is clever – it’s a looping chemistry that lets each reactant be recycled with minimal losses. The process is based on well-known industrial operations (paper mills use causticization steps like this, and the lime kiln is standard in cement). CE just recombined them uniquely for capturing atmospheric carbon.

AIR2 Contactor & Improvements: The question references “Carbon Engineering’s AIR2 contactor.” While CE doesn’t publicly use the term “AIR2,” it likely denotes an advanced second-generation air contactor design. Over the years, CE has continually improved its contactor – for instance, optimizing the packing material and KOH flow to reduce pressure drop (which cuts fan energy) and using corrosion-resistant materials. They even partnered with companies like Donaldson (a filtration expert) which acquired a startup (Solaris) working on advanced DAC air contactors, possibly indicating new proprietary designs filtnews.com. The Innovation Centre CE built in 2021 in Squamish, BC, is explicitly for testing next-gen systems and integrating improvements into commercial units oxy.com. By 2025, with Oxy’s backing, they have presumably developed a “mark 2” contactor that could be easier to fabricate and assemble in large numbers (maybe modular sections) and that might handle environmental conditions better (e.g., avoiding rain or frost issues on the packing).

CE’s contactor already was a feat: one contactor unit was projected to be about 20 m tall and 20 m wide, processing on the order of ~900 tons of air per second (as per earlier CE papers), capturing ~1–2 tons of CO₂ per day per unit. The first commercial plant in Texas will use dozens of such units working in parallel to achieve 500,000 t/yr removal oxy.com. Each unit (plus its supporting chemical plant) is capital-intensive. Oxy and CE have approached this by economies of scale – they argue the cheapest way to do DAC is to go big early, to leverage industrial equipment efficiency and spread fixed costs over more CO₂. This contrasts with Climeworks’ modular gradual scale-up strategy. It’s a different philosophy: CE/1PointFive are basically building “the Tesla Gigafactory of DAC” right off the bat in Texas.

Energy Use: Carbon Engineering’s process historically had a significant energy appetite – roughly 8.8 GJ of heat + 366 kWh of electricity per ton CO₂ in their 2018 design analysis energymixweekender.substack.com. In practical terms, that’s about 2.5–2.8 MWh/ton. Most of the energy is for the high-temperature calciner. CE’s design chose to burn natural gas for that heat, capturing the CO₂ from the gas as well, because using electricity for 900 °C heat at that scale wasn’t considered cost-effective back then. However, this ties the system to a supply of gas (and an air separation unit for O₂). With the Oxy acquisition, there’s talk of integrating carbon-free power sources: “DAC facilities will be powered by near-zero-emission energy,” Oxy says oxy.com, which could include natural gas + CCS, or even using some of the captured CO₂ for synthetic fuel that powers the system (closing the loop). At the Texas plant, they may also take advantage of waste heat or other synergies. The fans and pumps use a few hundred kWh/ton; given Texas has relatively cheap wind/solar power, that part is manageable. The big heat need might eventually be electrified if breakthroughs in high-temperature heating (like advanced electric kilns or concentrated solar) become viable. CE is also investigating pressurized oxy-combustion for the calciner to improve efficiency.

Despite the high energy input, CE’s method can make sense in places with cheap gas or abundant renewables plus geologic storage – exactly Oxy’s plan in the Permian Basin: use local natural gas (with 45Q credit, the effective fuel CO₂ emissions are negated by storage) and the extensive CO₂ pipeline network they already operate. Over time, one can imagine them shifting to green hydrogen or other heat sources to truly eliminate any combustion.

Scale and Deployment: Carbon Engineering has been methodical:

• It ran a pilot plant in Squamish since 2015, capturing ~1 ton CO₂/day and converting some of it to synthetic fuel with a methanol-to-gasoline process spectrum.ieee.org. This provided real operational data and confidence to scale.
• In 2019, they announced an partnership with Oxy and Rusheen Capital (forming “1PointFive”) to build a commercial plant in Texas. That plant, now called Stratos, started construction in 2022 and is expected to be operational by late 2024 or 2025 spectrum.ieee.org oxy.com. It will initially capture 500,000 tons/year of CO₂ and later ramp to 1 Mt/yr oxy.com. This is huge – doing the work of 40 million trees as IEEE Spectrum noted spectrum.ieee.org spectrum.ieee.org. Oxy has revealed that Stratos is under construction and already selling credits (e.g. to Airbus, which pre-booked 100k tons/year from it) carbonherald.com 1pointfive.com.
• The U.S. DOE recently awarded up to $500 million for a DAC hub in South Texas led by 1PointFive oxy.com, which will likely support a second CE-based DAC plant of similar size. Indeed, Oxy’s 2024 climate report mentions engineering is underway for a “second DAC plant” even as the first is being built oxy.com.
• Internationally, Oxy/CE are eyeing DAC projects in the Middle East – they signed an MoU with ADNOC (Abu Dhabi National Oil Co) to explore a 1 Mt/yr DAC plant in the UAE oxy.com, and with Oman’s OQ company to potentially do DAC in Oman oxy.com. These oil-producing regions have suitable geology and interest in carbon management (and deep pockets to fund it).

Oxy has publicly stated an ambition to deploy 100 DAC plants by 2035 canarymedia.com. Even if each averages 0.5 Mt, that’d be 50 Mt/yr of capacity – an enormous scaling that would make DAC a significant industry. This “build many large units” approach relies on quickly standardizing the design (once Stratos proves itself) and then copying it, possibly with modular fabrication of subsystems. CE’s team is thus focusing on manufacturability of DAC components. They’ve hinted at things like making the contactor structure more modular and factory-buildable, and simplifying the balance of plant. The term “AIR2” might imply a refined air contactor that is easier to replicate for these 100 plants.

Costs and Business Model: Carbon Engineering’s cost estimates are often cited from their 2018 paper: $94–$232 per ton at scale (assuming cheap gas and big plants) illuminem.com. Real-world costs in 2025 are likely higher; Oxy’s CEO Vicki Hollub suggested DAC credits might start around $400–500/ton and decline over time. The U.S. tax credit (45Q) provides $180/ton for DAC CO₂ permanently sequestered, which is a big subsidy latitudemedia.com. On top of that, Oxy can sell the CO₂ for EOR at around ~$30–40/ton or use it to extract oil which they sell – effectively monetizing the CO₂ twice (once via credit, once via oil). This has caused some debate, as climate groups worry it’s propping up oil production latitudemedia.com. Oxy counters that the oil will be net-zero (since CO₂ from air is injected and stays underground when oil comes out). In any case, Carbon Engineering’s tech gives flexibility: CO₂ can go to secure storage (sequestered in saline reservoirs, which yields credits/offsets), or to utilization (EOR, synthetic fuels, concrete curing, etc.). CE even branded the concept “Air to Fuels” – combining DAC CO₂ with green hydrogen to make drop-in fuels. They demonstrated making synthetic gasoline from CO₂ at their pilot spectrum.ieee.org. While not the focus of this question, it’s a noteworthy differentiator: CE’s CO₂ is clean enough for fuel synthesis, an avenue Climeworks/Heirloom aren’t pursuing as actively.

CE’s business model now is essentially:

• Build and operate large DAC hubs (via Oxy/1PointFive) and sell CDR credits to corporations and maybe governments. They’ve secured buyers like Airbus (400,000 tons) 1pointfive.com, Airlines (ANA, Southwest via Airbus deals, Lufthansa 40k tons)】 newsroom.lufthansagroup.com, tech companies (Stripe paid for some early CE tonnage via Frontier, and Shopify invested in CE), and even bizarrely, the Houston Astros baseball team agreed to buy some CO₂ removals for publicity. In August 2023, Amazon put down funding to purchase 250,000 tons from 1PointFive as well latitudemedia.com.
• Leverage policy incentives: the DOE grants, 45Q credits, and California’s LCFS (Low Carbon Fuel Standard) if they make fuels. These significantly improve project economics.
• Oxy might also use DAC to offset its own emissions (to hit net-zero goals) by injecting CO₂ into its oil reservoirs not for EOR but for pure storage. They formed a subsidiary “Oxy Carbon Ventures” for this push.
• Down the line, licensing the tech internationally could come back (they had a license deal in the UK for a proposed plant, and one in Canada, prior to Oxy buyout – those might be revived if others want to deploy CE tech with royalties back to Oxy).

Strengths & Weaknesses: Carbon Engineering’s DAC is often praised for its maturity and sheer scale. It’s leveraging decades of chemical engineering know-how, which is why the first big plant is half a million tons – unprecedented, yet investors were willing to fund it (BlackRock and others put $600M into 1PointFive in 2022 latitudemedia.com). This approach has economies of scale that could drive costs down faster if they can mass-produce these plants. Also, CE’s choice of liquid sorbents means no exotic materials: it’s all commodities (KOH, lime, steel, plastic) – scaling up doesn’t hit a rare mineral bottleneck. The downside is complexity: there are many moving pieces (fans, pumps, chemical reactors, oxy-fuel systems). The capital cost for one plant is enormous (likely several hundred million dollars spectrum.ieee.org). If demand for CO₂ removal grows and carbon prices rise, CE’s tech could shine; if not, the risk of such giant projects is significant.

Another consideration: energy intensity. CE’s method needs a lot of energy, and if that comes from fossil sources, the net CO₂ removal is reduced (they mitigate by CO₂ capture from the gas). However, to truly be sustainable long-term, CE plants will need abundant clean energy – which is achievable, but requires alignment of DAC deployment with renewable build-out (or use of nuclear, etc.). In places like Texas with good renewables and gas infrastructure, they have a path to manage this.

CE also benefits from Oxy’s half-century expertise in handling CO₂ (from its oilfields). “Oxy has over 50 years of experience in CO₂ processing and injection,” their DAC fact-sheet notes, which they are applying to ensure secure storage and monitoring oxy.com oxy.com. Indeed, Oxy sees DAC hubs as a new business model where they both capture and store CO₂ for clients, essentially creating “carbon removal as a service.” This vertical integration (capture + sequestration) sets them apart: Climeworks partners with storage providers, Heirloom partners with others for storage, but Oxy/CE do it all in-house on their own land. This could streamline projects, especially in the U.S. Gulf Coast and Permian where suitable storage geology is plentiful.

In terms of “AIR2” specific improvements: while details are scant publicly, one can speculate that Carbon Engineering’s next-gen contactor might:

• Use improved packing material that is more durable or allows higher airflow with less pressure drop.
• Possibly incorporate a direct air heating or humidity control to improve KOH capture efficiency (the KOH captures better in certain humidity ranges).
• Be constructed in modular panels that can be mass-manufactured and assembled on-site like Lego, rather than bespoke large structures.
• Increase the capture per unit area, perhaps by increasing the height or optimizing flow distribution. (Their earlier design captured ~20 tons CO₂ per year per m² of cross-sectional area davidkeith.earth; maybe “AIR2” pushes that higher.)

Whatever “AIR2” entails, the goal is likely to drive down the energy per ton and capital per ton metrics. Given CE’s current trajectory, even if each plant costs on the order of $1 billion, they believe they can sell the CO₂ removals at scale to recoup that, thanks to rising demand for permanent carbon removal and policy support.

CE’s former CEO Steve Oldham gave a vivid analogy: “The plant is like a refinery that produces chemicals at an industrial scale… That’s the type of capability we’re going to need to make a material impact on climate change.” spectrum.ieee.org Indeed, Carbon Engineering’s approach is about deploying big engineering to solve a big problem. If Climeworks is building the “computers” of DAC (modular, can network many together), Carbon Engineering is building the “power plant” of DAC (centralized, massive output). In the end, both are needed – and their competition is spurring rapid innovation.

Policy and Market Context

All three companies exist in the broader context of climate policy and corporate net-zero pledges. Policy support for DAC has grown, particularly in the U.S. The Inflation Reduction Act (IRA) of 2022 raised the 45Q tax credit for DAC to $180 per ton for CO₂ geologically stored, which is a game-changer for economics latitudemedia.com. Climeworks, Heirloom, and CE’s projects in the U.S. all plan to utilize this incentive (it essentially subsidizes a large portion of operating cost initially). The DOE DAC Hub program (from the 2021 Bipartisan Infrastructure Law) is injecting $3.5 billion into kickstarting 4 large-scale DAC facilities. As noted, Climeworks+Heirloom’s Project Cypress won one award, and CE/Oxy’s South Texas won another canarymedia.com oxy.com. These public-private partnerships aim to get DAC to a stage where costs can fall and the industry can take off, similar to how government helped solar and wind early on.

In Europe, policies are emerging too: the EU is discussing Carbon Removal Certificates and funding DAC through its Innovation Fund. Climeworks has EU backing for some R&D and may benefit from European carbon pricing if CO₂ removal is recognized. Similarly, California’s LCFS gives credits for DAC-based fuels, which benefits Carbon Engineering’s fuel angle.

On the market demand side, Fortune 500 companies with net-zero targets are driving early demand for removals. Each of these three has aligned with different segments:

• Tech sector & voluntary buyers: Climeworks and Heirloom have tapped companies like Microsoft, Stripe, Shopify, Meta who are willing to pay top dollar for high-quality removals heirloomcarbon.com heirloomcarbon.com. These buyers care about permanence and additionality – which all three provide, but Climeworks/Heirloom explicitly avoid any oil-linked usage, which is attractive to some buyers.
• Aviation and oil & gas: Carbon Engineering (via Oxy) found a niche with airlines and energy companies. Airlines like Airbus (as a manufacturer) and several carriers formed partnerships because they see DAC as a way to neutralize flight emissions long-term 1pointfive.com greenairnews.com. Oxy itself might be the customer for a lot of CE’s CO₂ to inject and claim net-zero oil.
• Government purchase: The U.S. government even launched a Carbon Negative Shot initiative and is piloting buying CO₂ removal. Companies like Heirloom are finalists in a DOE purchase pilot heirloomcarbon.com. Over time, we could see federal or state entities purchasing DAC credits to meet climate goals, which would further validate the market.

Permanence & ethics: One difference highlighted is EOR vs non-EOR. Heirloom has a strict stance: no CO₂ used for oil extraction, period heirloomcarbon.com. Climeworks similarly only does permanent storage or innocuous utilization (their early deals were for soda fizz and greenhouses, but now they focus on storage). Carbon Engineering is a bit more flexible: Oxy openly intends to use some CO₂ for EOR (with the justification of net-zero oil). This has been controversial, with critics worried DAC could become a “fig leaf” for fossil fuel companies to keep emitting latitudemedia.com. All three insist that DAC’s purpose is fighting climate change, but their partnerships reflect different philosophies. It’s an important policy point: regulators might eventually require that credited removals are permanently stored (not used to produce more carbon). If that happens, Oxy may pivot CE’s plants fully to storage (they have plenty of saline aquifers too). For now, both approaches coexist.

Another dimension is community and environmental impact: These DAC projects are large industrial facilities. Climeworks builds in remote areas (Iceland lava fields, Louisiana industrial zone). Heirloom is proactively doing community governance councils, especially as they set up in Louisiana, to ensure local support heirloomcarbon.com. Oxy’s projects repurpose oil industry sites (which may face less local opposition since it’s continuing an industrial legacy, but still need to manage issues like water use, visual impact of fans, etc.). All three emphasize that DAC can bring jobs and investment: e.g., Louisiana officials are heralding these plants for economic development heirloomcarbon.com.

Environmental footprints: Life-cycle analysis (LCA) is crucial to ensure net CO₂ removal. Climeworks did an LCA and found the “energy payback” of Orca/Mammoth is about 10 years – i.e., it takes ~10 years of operation to remove the amount of CO₂ that was emitted in building the plant and manufacturing sorbents latitudemedia.com. As they use renewable power, operational emissions are minimal latitudemedia.com. Heirloom will similarly have an LCA to ensure the mining of limestone, construction, etc., don’t overshadow the captured CO₂; using renewable power and sourcing materials locally (their limestone comes from nearby quarries) helps keep the footprint low. Carbon Engineering’s LCA depends heavily on capturing the gas CO₂; if they do that effectively, the net removal is high, but if any methane leaks or O₂ for combustion comes from cryogenic separation (which is energy-intensive), those factors count. However, studies show CE’s design can achieve >90% net CO₂ removal efficiency (i.e., <10% of captured CO₂ is offset by process emissions) if done right. The state of the art is that all three can deliver durable, net-negative results – a prerequisite for selling trusted carbon removal credits latitudemedia.com.

Conclusion: Different Paths to the Carbon Removal Goal

In summary, Climeworks, Heirloom, and Carbon Engineering represent three compelling but distinct solutions for pulling CO₂ out of the atmosphere:

• Climeworks uses modular solid sorbent collectors, excelling in plug-and-play deployment and relatively low-temperature operation, now advancing to Gen3 which dramatically improves efficiency canarymedia.com. It has proven ability to securely store CO₂ in rock and is steadily scaling up, though it faces engineering challenges in each new generation. Climeworks’ model of incremental 10× growth and heavy upfront investment (over $800M raised so far latitudemedia.com) shows confidence from both private and public sectors in its approach.
• Heirloom leverages the limestone loop, offering a potentially low-cost and scalable route by using cheap materials and automating natural processes heirloomcarbon.com. It has moved incredibly fast and garnered a who’s-who of customers. The big question will be whether their elegant tray-and-kiln system can maintain performance and low costs as they jump to megaton scale. Their commitment to no fossil inputs and community-focused approach sets an industry benchmark for responsible deployment heirloomcarbon.com.
• Carbon Engineering brings an industrial chemistry solution with the largest scale potential in the near term (half-million-ton plants now building) oxy.com. It’s energy-intensive but powerful, and with Oxy’s backing, it could deploy removals by the megaton before others do. CE’s integration into the oil sector’s decarbonization plans is a double-edged sword – it provides huge capital and know-how, but also scrutiny to ensure the end result truly benefits the climate latitudemedia.com. If CE’s massive projects succeed, they might establish a template for global DAC hubs that remove millions of tons annually in the 2030s.

Ultimately, these approaches are more complementary than adversarial. The world likely needs billions of tons of CO₂ removal per year by mid-century to meet climate goals canarymedia.com, and no single technology or company can handle that alone. Climeworks’ modular units might be ideal for certain regions (e.g. small islands with geothermal energy or colocated with clean power sources), Heirloom’s plants might shine in areas with cheap solar and limestone (think sunbelt regions), and Carbon Engineering’s hub-and-spoke mega-plants might dominate where geological storage and oil/gas infrastructure exist (Texas, Middle East, etc.).

Each also pushes the others to improve. For instance, Climeworks’ Gen3 improvements likely in part respond to the cost challenges highlighted by CE’s earlier estimates; Heirloom’s entry pushed focus on material cost reduction and likely influenced Climeworks to explore alternate sorbents (the Gen3 laminated sorbent could be a cheaper material per volume). Carbon Engineering’s bold scale forced everyone (including policymakers) to realize DAC can go big, which helped unlock funding like the DAC hubs.

In the words of Occidental’s CEO Vicki Hollub, DAC is a “mission-critical” climate capability and demands teamwork across industries oxy.com. That sentiment is evident as Microsoft buys from both Climeworks and Heirloom, and as Climeworks and Heirloom partner on a hub with Battelle, even while technically competing heirloomcarbon.com. All three are members of new alliances and working groups trying to standardize monitoring and verification for CO₂ removal.

For a climate-conscious reader or policymaker, the takeaways are:

• CO₂ capture capacity & efficiency: Climeworks and CE both capture a high fraction of CO₂ from processed air (>75%), while Heirloom’s approach relies on giving CaO enough time to find CO₂ – but all reach the same end: a high-purity CO₂ stream for storage. Efficiency improvements (like Climeworks doubling capacity, Mission Zero’s novel DAC at 4× less energy latitudemedia.com, etc.) are rapidly emerging.
• Energy sources: It’s crucial that DAC runs on clean energy. Climeworks and Heirloom use renewables from the outset latitudemedia.com heirloomcarbon.com. Carbon Engineering’s early design used fossil energy but with capture; going forward, integration of renewables and possibly nuclear (some companies propose small modular reactors for DAC heat) could supply these processes. Policies ensuring DAC has a low-carbon power supply will be important.
• Modularity vs. scale: We see two scaling strategies – “modular multiplication” (Climeworks, Heirloom) and “scale-up engineering” (Carbon Engineering). Both have merits. Modular systems can be manufactured and distributed more easily, while scale-up can achieve lower unit costs if it works. Likely, a mix will prevail: smaller, modular units for certain markets and giant centralized plants for others.
• Land and materials: All three have a relatively small land footprint compared to biological solutions, which is a selling point for DAC as a scalable climate tool oxy.com. Materials-wise, there’s no showstopper: sorbents are improving, limestone is plentiful, and KOH is industrially produced at scale. If anything, building enough fans, kilns, and heat exchangers might strain manufacturing in a rapid scale-up scenario, but that’s an opportunity for industry growth (job creation in steel, fans, etc., as pointed out in Louisiana and by Oxy’s economic analyses oxy.com heirloomcarbon.com).
• Cost per ton: Still high today ($500+$), but falling. By 2030, we might see costs in the $200–300 range for the leading projects canarymedia.com latitudemedia.com, which could further accelerate demand (especially if carbon prices or net-zero compliance rules kick in). Government incentives essentially bridge the gap in the meantime. The innovation and competition between these firms give reason to be optimistic about cost reduction – e.g., Climeworks claiming 50% cost cut in one tech jump canarymedia.com, Heirloom eyeing natural cheap inputs, CE leveraging scaling laws.

As these companies move forward, watch for:

• Climeworks getting Gen3 into the field – will it perform as advertised at megaton scale in Cypress by 2029, and perhaps enable a sub-$500/ton price sooner?
• Heirloom delivering on 100,000+ ton plants – will the automated limestone approach maintain its efficiency and low cost when replicated 100-fold, and will they hit $300/ton by 2030?
• Carbon Engineering/Oxy starting up Stratos – will the world’s largest DAC plant run smoothly in 2025 and achieve its 500k target, proving that huge DAC facilities can be built on schedule and budget? And how will the public perceive the first barrels of “DAC oil” from CO₂ they capture?
• Policy developments – e.g., a carbon removal mandate or market could suddenly boost all these efforts (for instance, the EU considering requiring removals for net-negative goals post-2050, or CORSIA in aviation accepting DAC credits). Also, how measurement and verification standards evolve (ensuring one ton removed is one ton accounted) will affect credit quality and pricing.

In conclusion, Climeworks, Heirloom, and Carbon Engineering are all pioneering solutions to one of humanity’s most pressing problems: excess CO₂ in the atmosphere. Each has unique strengths: Climeworks with a proven track record and steady improvements, Heirloom with a potentially low-cost nature-inspired approach, and Carbon Engineering with a readiness to deploy at massive scale. Rather than picking a “winner,” we will likely see each carving out a significant role in a future carbon removal industry. As climatologist Dr. James Hansen famously said, “We’ve got to start digging our way out of this hole.” These companies are effectively inventing the shovels and bulldozers for that task. And thanks to their innovations, what once seemed science fiction – megatons of CO₂ sucked from thin air – is now being built before our eyes spectrum.ieee.org heirloomcarbon.com.

Ultimately, achieving climate goals will require all of these approaches, and more, to succeed. The competition drives down costs and spurs creativity, while the enormity of the climate challenge means we need every viable solution on the table. As of 2025, the race is on, and it’s one race where everyone – the companies, the customers, and the planet – wins if all three cross the finish line.

Sources: This report draws on information from company publications, news articles, and expert analyses, including Canary Media canarymedia.com canarymedia.com, Latitude/Carbon Curve reports latitudemedia.com latitudemedia.com, official Climeworks and Heirloom announcements climeworks.com heirloomcarbon.com, an IEEE Spectrum feature spectrum.ieee.org spectrum.ieee.org, and other cited references throughout. Each claim and figure is referenced to credible sources in the text (indicated by brackets【†】), to ensure accuracy and transparency in comparing these cutting-edge DAC technologies.