Spiritus | Khosla Ventures backs effort to make orchards of lung-like material to absorb CO2 from air

Khosla Ventures backs effort to make orchards of lung-like material to absorb CO2 from air

CEO Charles Cadieu (L) and CTO Matt Lee standing in front of the future home of the Spiritus Orchard facility, located in the Western U.S. (The exact location is not yet public.)

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A successful serial entrepreneur and a seasoned chemical engineer with a decade of experience at one of the nation’s premier national labs have come together to develop and scale a new direct air capture technology that mimics the architecture of a human lung.

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The founders of the startup, named Spiritus after the Latin word for “breath,” began work in December 2021, and the company is officially coming out of stealth on Wednesday, with the announcement of an $11 million funding raise led by prominent Silicon Valley venture capital firm Khosla Ventures, with other investors including Page One Ventures.

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Spiritus has built a novel approach to direct air carbon capture that relies on a material that absorbs carbon dioxide passively. Critically, Spiritus has developed a particular architecture that mimics the alveoli in the lungs in order to maximize the surface area for carbon dioxide to make contact with the material.

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This lung-like material, technically called a “sorbent,” will be shaped in round balls and laid out like artificial fruits in a carbon-capture orchard, CEO Charles Cadieu and CTO Matt Lee told CNBC in a phone interview on Tuesday.

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When the lung-like “fruit” have been collected from the carbon “orchard,” they will be put in a container, where low heat will be applied to remove the carbon dioxide. The desorption process will be powered by clean energy to ensure the process is a not adding emissions to the atmosphere. Once the CO2 has been removed from the lung-like fruit, the sorbent can then be returned to the carbon orchard and reused.

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On Thursday, Frontier, a public benefit company owned by payment processing company Stripe which aims to support the nascent carbon removal industry, said Spiritus is one of 12 companies selected to remove carbon for Stripe, Shopify and the H&M Group.

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The sorbent developed by Spiritus, made to mimick the human lung.

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‘Mother nature’s the true artist’

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Lee worked at Los Alamos National Lab from September 2012 to June 2022 on a variety of chemical engineering advanced material projects, including some with national security and defense applications, as well as heat shields and laser fusion fuel target pellets similar to those used at the Lawrence Livermore National Laboratory to achieve a key milestone in nuclear fusion. He is a specialist in colloid science, which is the study of materials where particles of one substance are suspended in another.

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Lee hadn’t worked on carbon capture technology applications until Cadieu inspired him to consider the problem. The pair had known each other for about 15 years through a family friend and had enjoyed keeping tabs on each other’s projects.

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Previously, Cadieu co-founded Caption Health, a health care startup that uses artificial intelligence to assist in ultrasound scans. Caption Health received funding from the Bill and Melinda Gates Foundation in September 2020 for its capacity to enable non-experts to perform lung ultrasounds and was sold to GE Healthcare in February 2023. Also, Cadieu was a founding team member of IQ Engines, an image recognition software company which Yahoo acquired in 2013.

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When Cadieu approached Lee to consider carbon capture, Lee approached the problem with a philosophy he has carried through much of his career: “Mother nature’s the true artist and she’s had a lot more practice than we have had,” Lee told CNBC. The other prong of his philosophy is summarized by a Leonardo da Vinci quote Lee recounted: “Simplicity is the ultimate sophistication.”

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That’s why they looked at lungs.

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Matt Lee, the chief technical founder, is a chemical engineer with an expertise in colloid science, which is the study of materials where particles of one material are suspended in another.

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“Lungs are very well rehearsed at doing this — taking a large volume of air and then dispersing it or spreading it out over an extraordinary high amount of interface that the alveoli make with other parts of the body,” Lee told CNBC. That’s important because while carbon dioxide levels in the atmosphere are at record high levels, carbon dioxide is still diluted and makes up a relatively small percentage of the air.

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“In order to capture some significant quantities of carbon dioxide on your sorbent, you simply have to expose it to a lot of air — a massive amount — and so finding the structure that can simultaneously give you that highly efficient contact with a large amount of active surface per unit volume enables you to have a process that is viable, feasible, economical,” Lee told CNBC.

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That third component — economical — is critical in the direct air carbon capture field, and is part of what drew Khosla Ventures to make its first direct air capture investment in Spiritus.

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“We’ve been watching on the sidelines evaluating all the technologies,” Rajesh Swaminathan, partner at Khosla Ventures, told CNBC in a phone conversation on Tuesday. Direct air capture is still a nascent industry and therefore very expensive right now, but Spiritus uses less energy than most of the other competitors in the space, Swaminathan said.

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The absorption of carbon dioxide is passive, and the desorption process, where the carbon dioxide is removed from the “fruit” made with the lung-like material, takes a comparatively low amount of energy, Swaminathan said.

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This is a model of the Spiritus equipment used to remove carbon dioxide from the sorbent.

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“A lot of direct air capture processes, they require either a lot of high heat — and ours requires low heat — or they require a lot of energy, even if low heat, and ours is less than half of what’s been previously achieved by other solutions,” Cadieu told CNBC. “So this is another part of this overall equation that drives down low costs.”

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The U.S. Department of Energy has a public initiative called the “Carbon Negative Shot,” which is its name for the push to drive innovation that can capture carbon dioxide, remove it from the atmosphere and store it for less than $100 per metric ton. Spiritus is driving towards this $100 per metric ton goal.

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Spiritus will partner with companies specializing in carbon sequestration to take that removed carbon and put it away.

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Cadieu says the artificial carbon orchards that Spiritus plans to build are more efficient than biologic trees and so take a smaller land footprint to absorb carbon dioxide than biologic forests. When the carbon captured with artificial trees is stored, it also has the advantage of sequestering carbon permanently. When biologic trees decompose after they die or burn in a fire, carbon they contain is released back into the atmosphere.

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“We’re able to remove about 1,000 times more carbon dioxide than a forest can. And so this solution is actually far more efficient than forestry for removing carbon dioxide from the atmosphere per acre,” Cadieu said.

Rewind.earth

Biomass carbon removal and storage

Tel Aviv, Israel

R&D

Rewind.earth uses cranes off of boats to sink agricultural and forest residues to the oxygenless bottom of the Black Sea, the largest anoxic body of water on Earth. Oxygenless water dramatically slows biomass decomposition. The lack of living organisms in the Black Sea limits any potential ecosystem risks. This process allows for affordable and environmentally safe carbon removal.

Carboniferous

Biomass carbon removal and storage

Houston, TX, US

R&D

Carboniferous sinks bundles of leftover sugarcane fiber and corn stover into deep, salty, oxygenless basins in the Gulf of Mexico. The lack of oxygen in these environments–and therefore absence of animals and most microbes–slows the breakdown of biomass so it is efficiently preserved and stored durably in ocean sediments. The team will conduct experiments to determine the functional stability of sunken biomass as well as the interaction with ocean biogeochemistry.

Vycarb

Ocean alkalinity enhancement

Brooklyn, NY, US

58 tons

Vycarb uses a reactor to add limestone alkalinity to coastal ocean water, resulting in the drawdown and storage of atmospheric CO₂. Their dissolution system has a novel sensing apparatus that base tests water, dissolves calcium carbonate, and doses alkalinity into the water at a controlled amount safe for dispersion. Their closed system makes it easier to measure the amount of dissolved alkalinity added and CO₂ removed.

Arbon

Direct air capture

New York, NY, US

173 tons

Arbon uses a 'humidity-swing' process to capture CO₂ from the air. The sorbent binds CO₂ when dry and releases it when wet. This process uses less energy than approaches that rely on changing temperature and pressure to release CO₂. The sorbent’s ability to bind CO₂ has been shown to remain stable over thousands of cycles. Both of these innovations could reduce the cost of DAC.

Vaulted

Biomass carbon removal and storage

Houston, TX, US

1,666 tons

Vaulted injects organic waste into durable wells, where the carbon in the waste is sequestered as it decomposes. Using a specialized slurry injection technology, their process can handle a wide range of organic carbon sources with minimal energy and upfront processing. Their system has the potential to be deployed quickly at large scales.

Spiritus

Direct air capture

Los Alamos, NM

713 tons

Spiritus uses a sorbent made from commercially-available materials and a passive air contactor that requires little energy to capture CO₂. The CO₂-saturated sorbent is then regenerated using a novel desorption process, capturing the CO₂ and allowing the sorbent to be reused with less energy than a higher-heat vacuum chamber typically used in direct air capture approaches. The high-performance, inexpensive sorbent and lower regeneration energy provide a path to low cost.

Planetary

Ocean alkalinity enhancement

Nova Scotia, Canada

937 tons

Planetary harnesses the ocean for scalable removal. They introduce alkaline materials to existing ocean outfalls like wastewater plants and power station cooling loops. This speeds up the sequestration of CO₂ safely and permanently as bicarbonate ions in the ocean. Planetary then verifies the removal through advanced measurement and modeling techniques.

Mati

Enhanced weathering

US and India

1,513 tons

Mati applies silicate rock powders to agricultural fields, starting with rice paddy farms in India. These rocks react with water and CO₂ to produce dissolved inorganic carbon that is subsequently stored in the local watershed and eventually in the ocean. Mati relies on rice field flooding and higher subtropical temperatures to accelerate weathering, and extensive sampling and soil and river modeling to measure removal and deliver co-benefits to smallholder farmers.

Holocene

Direct air capture

Knoxville, TN, US

332 tons

Holocene captures CO₂ from air using organic molecules that can be produced at low cost. In the first step of their process, CO₂ is captured from air when it comes into contact with a liquid solution. In the second step, a chemical reaction crystallizes the material as a solid. That solid is heated up to release the CO₂, minimizing energy wasted in heating water. Holocene’s process runs at lower temperatures, further reducing the energy required, increasing energy flexibility, and lowering overall cost.

EDAC Labs

Enhanced weathering

Baltimore, MD, US

317 tons

EDAC Labs uses an electrochemical process to produce acid and base. The acid is used to start the recovery of valuable metals from mining waste, and the base is used to capture CO₂ from air. The acid and base streams are then combined to produce metals that can be sold for applications such as batteries, and solid carbonates, which permanently store CO₂.

CarbonRun

Ocean alkalinity enhancement

Nova Scotia, CA

1,291 tons

CarbonRun enhances the natural ability of river currents to weather abundant, low-cost limestone and reduce river acidity levels. This benefits river ecosystems locally and enhances the rivers’ ability to capture CO₂ from the atmosphere. Rivers, which are natural carbon transport systems, then deliver CO₂ to the ocean for permanent storage in the form of bicarbonate.

CarbonBlue

Direct ocean removal

Haifa, Israel

400 tons

CarbonBlue uses calcium in a closed-loop cycle to mineralize, separate, and remove dissolved CO₂ from water. This results in a pure stream of CO₂ that can be durably sequestered. Their approach can operate in freshwater or saltwater and can rely on waste heat for the regeneration process. The team plans to integrate with desalination plants and other water-withdrawing industries, reducing energy usage and costs.

Carbon Atlantis

Direct air capture

Munich, Germany

275 tons

Carbon Atlantis is using a process known as electrochemical pH-swing. Their system uses a solvent to capture CO₂ and an acid to release it. This approach is inspired by recent innovation in Proton Exchange Membrane fuel cells and electrolyzers, making the process both cost-effective and energy-efficient. The CO₂ is then run through

Banyu Carbon

Direct ocean removal

Seattle, WA, US

360 tons

Banyu Carbon uses sunlight to capture CO₂ from seawater. A reusable, light-activated molecule that becomes acidic when exposed to light causes carbon dissolved in seawater to degas as CO₂, which is then stored permanently. Because only a small portion of the visible light spectrum is needed to trigger the reaction, this is a highly energy-efficient approach to direct ocean removal.

Alkali Earth

Enhanced weathering

Northfield, MN, US

1,351 tons

Alkali Earth uses alkaline byproducts from industrial processes as carbon-removing gravel to apply to roads. These minerals act as a sink for atmospheric CO₂, storing it permanently while cementing road surfaces. The formation of CO₂-containing minerals within the gravel can be directly measured, leading to high-confidence in resulting removals.

Airhive

Direct air capture

London, UK

943 tons

Airhive is building a geochemical direct air capture system using a sorbent that can be made out of cheap and abundant minerals. This sorbent reacts rapidly with atmospheric CO₂ when mixed with air in Airhive’s fluidized bed reactor. Coupled with a regeneration process that’s powered by electricity to release the CO₂ for geologic storage, this provides a promising approach to low-cost DAC.