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Innovation in Focus as DAC Technology Matures

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Direct air capture (DAC) is one of the most exciting emerging technologies in the burgeoning carbon-removal industry. Proponents see it as a key to achieving negative global emissions since it can access and trap carbon dioxide that is already in the atmosphere, although reducing CO2 pollution and capturing emissions at the point of combustion will remain top priorities. But DAC undeniably will have a role to play in decarbonization efforts as long as the technology can be scaled up and the costs can be driven down significantly.

A growing list of companies are hoping to do just that by either proving the scalability and feasibility of existing technologies or pushing the bounds of engineering and materials science to uncover even better and more cost-effective approaches to pulling diffuse CO2 from ambient air.

Government funding and private incentive and accelerator programs are trying to speed the process along by creating markets for captured CO2 and rewarding innovation. The US Department of Energy last week launched a $3.5 billion program to fund four DAC projects across the country that can prove their ability to capture and store or utilize at least 1 million tons of CO2 a year, part of a larger package funding carbon-removal efforts.

Three companies — Carbon Engineering, Climeworks and Global Thermostat — make up what is widely considered to be the top tier of DAC technology players today, each with its own approach to capturing CO2. All three have been around for at least a decade and have helped bring DAC technology into the limelight. Unsurprisingly, these three have developed some of the most mature approaches to direct air capture.

Leading Direct Air Capture Companies
 ClimeworksCarbon Engineering Global Thermostat
LocationSwitzerlandCanadaUS
System typeSolid sorbentLiquid solventSolid sorbent
Thermal energy needs80-120°C900°C105-120°C
Thermal energy sourceNon-fossil (geothermal, waste heat, etc.)Natural gas w/ CCSEnergy resource agnostic
Projects15 plants in Europe with collective capacity of about 6,000 tons CO2/yrPilot plant in Canada; developing plant in Texas of 1 million tons CO2/yrTwo plants in US with collective capacity of 1,500 tons CO2/yr
InvestmentsMost recent round of funding reached $650 million (March 2022)Received $70 million in total investments Received investments of $68 million in most recent round (2019)

Ripe for Innovation

In simple terms, DAC works by exposing atmospheric air to chemicals or other materials that attract CO2 molecules, and then applying heat or other conditional changes to the material to release the CO2. The capture material in most instances is a solid sorbent, but some systems use a hydroxide-based liquid solvent. In all cases, the capturing material must be “regenerated” and put back into the capture-and-release cycle.

The sorbent material itself and the method of releasing the CO2 are two areas most ripe for innovation today. North Carolina-based Sustaera has developed a proprietary sorbent it believes it can commercialize. Boston-based Verdox is known for its unique "electroswing adsorption" approach to capture and release, which it says can reduce DAC energy consumption by 70% compared to conventional approaches.

While these technologies and others may push the envelope, improving efficiency throughout the system will be the key to future cost reductions, says DAC pioneer Klaus Lackner, the director of the Center for Negative Carbon Emissions at Arizona State University. “Ultimately it’s a systems issue,” he tells Energy Intelligence. “It’s not one part, it's everything.”

Solving Solvents

In DAC circles, Canada-based Carbon Engineering is virtually synonymous with the solvent-based approach to capture. Solvents can be extremely effective at absorbing CO2 and are also often used in point-source carbon capture. Point-source technology providers such as Norway's Aker Carbon Capture and Shell-owned Cansolv are thought to be working on possible DAC applications as well.

The downside to liquid solvents is that their effectiveness at capturing CO2 also makes it very difficult to separate it back out. Carbon Engineering’s system requires 800ºC-900ºC of heat to release the captured CO2, which also means it needs a high-quality — and likely high-emitting — heat source to enable the process.

As a result, solvent-based DAC projects must be built at tremendous scale to be economical, requiring substantial financing and most likely a direct monetization scheme for the captured CO2. To wit, Carbon Engineering’s partnership with Occidental Petroleum to build a 1 million ton per year DAC plant and use the captured CO2 for enhanced oil recovery in Texas has been instrumental in the company’s ability to scale up.

Novel Technologies: DAC Start-Ups to Watch
Company LocationKey TechnologyNotable Investors/PartnersProject Status
Carbon CollectIreland"MechanicalTrees," solid ion-exchange resin tiles, moisture swingArizona State University Pre-deployment preparation
HeirloomUSSolid oxide sorbent derived from minerals, passive contactingBreakthrough Energy Ventures, Carbon Direct, Lowercarbon Capital, Ahren Innovation CapitalPre-pilot R&D
Mission ZeroUKSolvent-based capture, electrochemical separationBreakthrough Energy Ventures, Deep Science VenturesPilot in 2023
SustaeraUSSolid alkali metal sorbent on ceramic monolithsBreakthrough Energy Ventures, Neglected Climate Opportunities (Grantham Trust) Pilot in 2022
VerdoxUSSolid quinone sorbent, electroswing adsorptionBreakthrough Energy Ventures, Prelude Ventures, Lowercarbon Capital Pilot in 2022

Do Me a Solid

Because most start-up DAC players don’t have the history or the resources of a company like Carbon Engineering, solid sorbent is a more common approach. These types of capture projects can be easily modularized, which allow them to be more fit-for-purpose and flexible in terms of sizing and where they can be installed, while economies of scale can be achieved through mass production rather than through megaprojects. Solid sorbents, like the conventional "amines" used by Climeworks and Global Thermostat, also require far less heat to release the captured CO2 — typically between 80ºC and 140°C — which means the most energy-intensive part of the process can be powered by electricity generated from renewable sources.

The tradeoff for solid sorbents are the higher costs and questionable durability of the material. It can cost around $1,000 per kilogram to manufacture certain solid sorbents, says Julio Friedmann, chief scientist at Carbon Direct, an investment and advisory firm focused on carbon removal. That makes the performance and longevity of the capture material a key consideration, he says.

“There is an enormous, enormous range of physical sorbents, and most of them don’t come close to performing, but many of them are good enough that you can imagine a business based on it,” Friedmann tells Energy Intelligence. Advanced computing has quickened the pace of research into sorbent technology, Friedmann says, because it “has allowed us to both design these things and anticipate performance so … you can high-grade which class and which specific kinds of sorbents you want to use.”

The key is to find a sorbent that can quickly capture CO2 — in days, not weeks, Friedmann says — and capture a lot of it. Emerging sorbent materials like metal organic frameworks and zeolites are proving quite effective at maximizing CO2 “loadings,” he says. The energy required to release the CO2 is another important consideration. “You’re looking for the sorbents that have both fast kinetics and low energy requirements," he says. "That’s the ‘Goldilocks zone’ you’re shooting for."

Topics:
Emerging Technologies, Carbon Capture (CCS)
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