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Greenhouse Gases

XPrize Carbon Removal selects 15 milestone winners

Each team will get $1 million of Elon Musk’s money to develop their carbon removal concept

by Craig Bettenhausen
April 27, 2022 | A version of this story appeared in Volume 100, Issue 15


An artists rendering shows a large, C-shaped array of solar panels around a small chemical plant, all of which is floating in the ocean.
Credit: Captura
Participants in the Carbon Removal XPrize have grand designs like this floating electrochemical plant, proposed by Captura, that pulls CO2 out of seawater.

As Elon Musk was busy buying Twitter, the XPrize Foundation announced the 15 teams that will each take $1 million of his fortune and use it to develop their concepts to remove large quantities of carbon dioxide from Earth’s atmosphere. Musk’s personal foundation has pledged to donate a total of $100 million in prize money.

The start-up Calcite Carbon Removal, for example, won for a direct air capture (DAC) technology that cycles between calcium hydroxide, Ca(OH)2, and calcium carbonate, CaCO3, to pull CO2 out of the air and isolate it for transport and sequestration.

Another DAC-based winner, Verdox, is an early mover in electrochemical carbon capture, a promising but unproven route that avoids solvents and heat, two big cost drivers in many DAC systems. Verdox’s electrodes switch between CO2 absorbing and releasing modes with a change in applied voltage. The firm will sequester its carbon with Carbfix, a CO2 mineralization company that is also working with another milestone winner, Heirloom, and the DAC industry leader Climeworks.

An approach that’s been gaining attention recently is DAC’s aquatic cousin, direct ocean carbon capture. The California Institute of Technology spin-off Captura got its $1 million for a system that uses membranes, silver and copper electrocatalysts, and a potassium ferrocyanide/ferricyanide electrolyte to convert CO2 dissolved in seawater into carbon monoxide, ethylene, and small alcohols. Captura plans to build a floating prototype powered by renewable energy.

The foundation gave away $5 million across 23 student-led teams in November. The $50 million grand prize and $30 million runner-up pool are still up for grabs, and XPrize officials say any project could win, even if it wasn’t among the awardees so far.

$1 million each

XPrize’s 15 milestone-winning projects ply their carbon-removal methods on land, air, sea, and rock.


Calcite Carbon Removal: Calcium mineral cycle

Carbyon: Temperature swing membranes

Heirloom: Mineral sorbent cycle with subsurface mineralization

Sustaera: Mineral sorbent cycle

Verdox: Electrochemical scrubbing with subsurface mineralization


Bioeconomy Institute: Biochar soil amendment and bio-oil chemical feedstock

Global Algae Innovations: Reforestation and algae agriculture

NetZero: Biochar soil amendment and biomass power generation

PlantVillage: AI-powered regenerative agriculture

Takachar & Safi Organics: Biochar soil amendment


Captura: CO2 capture using electrolysis and separation membranes

Marine Permaculture SeaForestation: Seaweed for soil amendment and seafloor long-term storage

Planetary: Ocean alkalinization using upgraded mine waste


Carbin Minerals: Carbon mineralization using waste from mines

Project Hajar: Electrochemical capture with peridotite mineralization.



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