Ambient weathering of magnesium oxide for CO2 removal from air

Abstract

To avoid dangerous climate change, new technologies must remove billions of tonnes of CO 2 from the atmosphere every year by mid-century. Here we detail a land-based enhanced weathering cycle utilizing magnesite (MgCO 3) feedstock to repeatedly capture CO 2 from the atmosphere. In this process, MgCO 3 is calcined, producing caustic magnesia (MgO) and high-purity CO 2. This MgO is spread over land to carbonate for a year by reacting with atmospheric CO 2. The carbonate minerals are then recollected and re-calcined. The reproduced MgO is spread over land to carbonate again. We show this process could cost approximately $46-159 tCO 2 −1 net removed from the atmosphere, considering grid and solar electricity without post-processing costs. This technology may achieve lower costs than projections for more extensively engineered Direct Air Capture methods. It has the scalable potential to remove at least 2-3 GtCO 2 year −1 , and may make a meaningful contribution to mitigating climate change.

Geochemical Negative Emissions Technologies: Part I. Review

“…Surficial mineralization processes have been proposed that fit this definition. For example calcium oxide (Hanak et al, 2017;Hanak and Manovic, 2018) or magnesium oxide (McQueen et al, 2020) looping systems. Calcium looping is a pre-or post-combustion CO 2 capture technology which uses high temperatures.…”

Perspective - the need and prospects for negative emission technologies - direct air capture through the lens of current sorption process development

“…Those based on bioenergy with carbon capture and storage or BECCS [8,9] have been an early frontrunner, but this approach may have significant land use requirements [10]. More recent NET developments have focused on direct air capture (DAC) [11,12] and mineralization [13]. There remain many challenges with these technologies, and this provides significant opportunities for chemical engineering research and development over the next decade.…”

Alkalinity Concentration Swing for Direct Air Capture of Carbon Dioxide

“…Other approaches that store carbon in a more durable form include bioenergy with carbon capture and storage, [12] carbon mineralization processes that remove CO 2 directly out of the air, [13] or the addition of alkalinity to oceans, which increases dissolved carbon and ultimately drives the production of carbonate sediments [14–17] . Mineralization processes could result in the long‐term storage of concentrated CO 2 streams in subsurface formations, products such as concrete, as well as mine tailings and alkaline industrial wastes [6,18] …”