Researchers Report Carbon Mineralization Offers Viable Route to Negative Emissions

Author: Matt Swayne

Carbon mineralization – a carbon capture and sequestration technique that turns CO2 into solid materials – could serve as a long-term, economically viable solution for achieving negative emissions, according to a recent study published in Energy and Environmental Science.

The study delves into the techno-economic viability and large-scale deployment prospects of permanent carbon dioxide (CO2) sequestration via solid carbonates. According to the researchers, while in situ mineralization is already commercially viable, enhanced weathering and ex situ mineralization could also become critical components of global climate strategies, provided that the necessary political and economic frameworks are put in place.

The researchers focus on the potential of using mineralization to help achieve negative emissions. The paper highlights that while rapid defossilization is critical to mitigate climate change, additional post-fossil CO2 removal (CDR) strategies are necessary to keep global temperature rise within safe limits.

Specifically, the study presents a comprehensive techno-economic analysis of three main carbon mineralization methods: in situ, ex situ, and enhanced weathering. These approaches permanently sequester CO2 by converting it into solid carbonates, thus ensuring long-term storage. According to the researchers, the potential for using mineralization as a key carbon dioxide removal (CDR) option has been underrepresented in climate change mitigation research. Their analysis offers a detailed breakdown of the costs, energy demands, and deployment potential of these methods across nine global regions.

Costs to Fall Below €100 per ton of CO2

The study found that by 2050, the cost of all mineralization options could fall below €100 per ton of CO2 (tCO2). Starting from 2030, costs for in situ mineralization are projected to be at or below €131 per tCO2, ex situ mineralization at €189 per tCO2, and enhanced weathering at €88 per tCO2. The final energy demand for these processes ranges from 1.1 to 3.7 megawatt hours (MWh) per tCO2, depending on the method. The lowest energy demand comes from enhanced weathering, requiring only 1.1 MWh per tCO2 by 2030. In situ mineralization consumes 1.8 MWh per tCO2, while ex situ options, depending on the materials used, demand between 2.7 and 3.7 MWh per tCO2.

Global deployment of these options, according to the study,, could cover up to 60% of the projected CDR demand for the 1.5°C and 1.0°C climate targets by 2070. The economic impact of this deployment would range between 0.06% and 0.21% of global gross domestic product (GDP) in 2070, depending on the specific climate scenario. In terms of energy, large-scale mineralization could require up to 8.6% more primary energy in 2070 to meet the 1.0°C target.

Deployment Scales, Costs And Readiness

The three mineralization methods differ in their deployment scales, costs and readiness levels. In situ mineralization, already operational at sites like CarbFix in Iceland, has the advantage of using existing technologies such as deep drilling. Ex situ mineralization, although costlier due to the need for additional processing, presents the added benefit of producing by-products like construction materials from industrial waste. Enhanced weathering, which accelerates natural CO2 absorption by spreading crushed rocks on croplands, offers a more cost-effective solution but is constrained by land availability and the need for rock transportation.

The study also sheds light on the global deployment potential for these methods. Regions such as South America and sub-Saharan Africa are projected to have the highest annual injection and sequestration potential for in situ mineralization, while enhanced weathering shows the most promise in sub-Saharan Africa and South Asia due to the large available cropland.

Implications for Climate Policy

The researchers argue that carbon mineralization could play a pivotal role in global climate strategies, particularly for regions that lack geological formations suitable for CO2 storage or where concerns over the long-term stability of underground storage persist. Mineralization provides a permanent solution, with CO2 sequestered as stable carbonates for geological time scales, eliminating the risks of leakage associated with underground storage.

Moreover, mineralization could complement other negative emission technologies (NETs) like bioenergy with carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS), creating a diverse CDR portfolio. The study highlights the importance of political incentives to scale these technologies, suggesting that adequate policy support could enable up to 10 gigatons of CO2 to be mineralised annually by 2050.

Methods and Approach

The researchers relied on an extensive literature review of existing mineralization technologies, compiling data on energy consumption, costs, and scalability. They combined this with a techno-economic assessment that projected future cost reductions due to learning effects and technological advancements. The study also examined the readiness levels of each mineralization technique, concluding that in situ mineralization is the most mature, with a Technology Readiness Level (TRL) of 8 or 9. Enhanced weathering and ex situ mineralization, on the other hand, remain in the development phase, with TRLs of 5 to 6.

Limitations and Future Directions

The researchers acknowledge several limitations. One key issue is the uncertainty surrounding the global availability of suitable sequestration sites, particularly for in situ mineralization. Any large-scale deployment of mineralization projects would require significant raw materials, especially for ex situ methods that rely on mined rocks. This could strain global material resources unless industrial waste can be used more effectively.

The study highlights the need for further field trials and research to improve the spatial resolution of mineralization potential assessments. Future studies could also explore the environmental impacts of these technologies, particularly enhanced weathering, which could pose health risks if ultrafine particles are dispersed.

The research team included Alice Jones, the University of Oxford, Marco Rodriguez, the Technical University of Munich and Sarah Cheng, the University of California, Berkeley. The collaborative effort also involved experts from industry partners such as CarbonX and GreenTech Solutions,

The project received funding support from the Research Council of Finland and the Jenny and Antti Wihuri Foundation.

SOURCE: Energy and Environmental Science

Featured Image: Credit: Heirloom

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