Minimizing cost is the key parameter for the viability of direct-air-capture (DAC) systems that remove carbon dioxide from the atmosphere. The startup company Sustaera Inc. (Research Triangle Park, N.C.; www.sustaera.com) has built a prototype DAC system that it says can achieve operational efficiencies that are 3–4 times higher than existing DAC technologies. The company has also designed its system to be modular in nature, so that it can be scaled for smaller capital costs than existing technologies.
“We are on the path to direct-air capture for less than $100 per ton of CO2 removed,” says Sustaera chief technology officer Cory Sanderson, citing an often-stated cost goal of the DAC community.
Sustaera’s DAC system is unique in several ways that allow it to achieve greater efficiencies and lower costs. First, the company has developed a proprietary, nanostructured solid sorbent material made of low-cost materials. Second, Sustaera has secured patents for the amino-acid-salt it uses for the adsorption step. “These salts of amino acids achieve adsorption-desorption kinetics that are similar to conventional amine-based DAC technology, but the molecules are thermally and oxidatively more stable. Thousands of absorption/desorption cycles have been completed without breakdown of the sorbent material,” Sanderson says.
Source: Sustaera
Next, the Sustaera prototype uses electro-resistive heating, rather than steam-based heat, to recover the captured CO2 from the sorbent material. “Fundamental thermodynamics limits thermal efficiency of steam-based heating to around 40%,” explains Sanderson. “Using electric current when heating the sorbent to release CO2 unlocks capture efficiencies of 90%,” he notes.
Last, the modular DAC system is engineered to access intermittent renewable power, allowing it to utilize the lowest-cost power by purchasing power when it is cheapest. Startup can be achieved by the all-electric system in a few minutes.
Sustaera’s methodology for determining efficiencies and costs has been third-party verified, Sanderson says, and the company has been testing its prototype on outside air. The company is looking for partners to build a commercial pilot unit. Sustaera is currently funded by venture capital, along with a U.S. Department of Energy grant and funds from the X-Prize for Carbon Removal.