Weekly CDR Publication Highlights
This week’s selected publications cover issues pertaining to the use of direct air capture for the achievement of climate neutrality in aviation, use of olivine as part of ocean alkalinity enhancement and marine enhanced rock weathering, how rock mineralogy effects transfer of CO2 when a saline aquifer is used for the purpose of carbon sequestration, use of macroalgae products for carbon dioxide removal purposes and the use of polyethyleneimine-functionalized graphane oxide aerogels for direct air capture.
The Role of Direct Air Capture in Achieving Climate-Neutral Aviation
Abstract:
Growing demand for air travel and limited scalable solutions pose significant challenges to the mitigation of aviation’s climate change impact. Direct air capture (DAC) may gain prominence due to its versatile applications for either carbon removal (direct air carbon capture and storage, DACCS) or synthetic fuel production (direct air carbon capture and utilization, DACCU). Through a comprehensive and time-dynamic techno-economic assessment, we explore the conditions for synthetic fuels from DACCU to become cost-competitive with an emit-and-remove strategy based on DACCS under 2050 CO2 and climate neutrality targets. We find that synthetic fuels could achieve climate neutrality at lower cost than an emit-and-remove strategy due to their ability to cost-effectively mitigate contrails. Under demand reductions, contrail avoidance, and CO2 neutrality targets the cost advantage of synthetic fuels weakens or disappears. Low electricity cost (€0.02 kWh-1) and high fossil kerosene prices (€0.9 l-1) can favor synthetic fuels’ cost-competitiveness even under these conditions. Strategic interventions, such as optimal siting and the elimination of fossil fuel subsidies, can thus favor a shift away from fossil-reliant aviation.
Brazzola, N., Meskaldji, A., Patt, A., Trondle, T. & Moretti, C. (2025) The Role of Direct Air Capture in Achieving Climate-Neutral Aviation. Nature Communication.
Read the full paper here: The Role of Direct Air Capture in Achieving Climate-Neutral Aviation I Nature Communication.
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Ocean Alkalinity Enhancement and Carbon Dioxide Removal through Marine Enhanced Rock Weathering Using Olivine
Abstract:
Marine enhanced rock weathering (mERW) is increasingly receiving attention as a marine-based carbon dioxide removal (CDR) technology. The method aims to achieve ocean alkalinity enhancement (OAE) by introducing fast-weathering rocks into coastal systems. The latter is envisioned to act as a large natural biogeochemical reactor, where ambient physical and biological processes can stimulate rock dissolution, thus generating a concomitant alkalinity release and increasing the seawater’s capacity to sequester CO2. Olivine has been put forward as the prime candidate mineral for mERW, but at present, no peer-reviewed results are available from larger-scale field studies in coastal areas, so the information about olivine dissolution in marine systems is largely derived from laboratory experiments. As a result, key uncertainties remain concerning the efficiency, CO2 sequestration potential, and impact of olivine-based mERW under relevant field conditions. In this review, we summarize recent research advancements to bridge the gap between existing laboratory results and the real-world environment in which mERW is intended to take place. To this end, we identify the key parameters that govern the dissolution kinetics of olivine in coastal sediments and the associated CO2 sequestration potential, which enable us to identify a number of uncertainties that still remain with respect to the implementation and upscaling of olivine-based ERW, as well as monitoring, reporting, and verification (MRV). From our analysis, we conclude that the current knowledge base is not sufficient to predict the outcome of in situ mERW applications. Particularly, the impact of pore-water saturation on the olivine dissolution rate and the question of the additionality of alkalinity generation remain critical unknowns. To more confidently assess the potential and impact of olivine-based mERW, dedicated pilot studies under field conditions are needed, which should be conducted at a sufficiently large spatial scale and monitored for a long enough time with sufficient temporal resolution. Additionally, our analysis indicates that the specific sediment type of the application site (e.g., cohesive versus permeable) will be a critical factor for olivine-based mERW applications, as it will significantly impact the dissolution rate by influencing the ambient pore-water pH, saturation dynamics, and natural alkalinity generation. Therefore, future field studies should also target different coastal sediment types.
Geerts, L., Hylèn, A. & Meysman, F. (2025) Ocean Alkalinity Enhancement and Carbon Dioxide Removal through Marine Enhanced Rock Weathering Using Olivine. European Geosciences Union.
Read the full paper here: Ocean Alkalinity Enhancement and Carbon Dioxide Removal through Marine Enhanced Rock Weathering Using Olivine I European Geosciences Union.
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Impact of Rock Mineralogy on Reactive Transport CO2 during Carbon Sequestration in a Saline Aquifer
Abstract:
Deep saline aquifers offer a vast long-term storage capacity for CO2. The diverse mineral compositions in CO2 geological storage systems complicate the reactive transport of CO2. Despite extensive research on carbon sequestration in saline aquifers, the impact of rock mineralogy on the CO2 trapping mechanisms needs further investigation. This study addresses this gap by employing numerical simulations to investigate how different minerals affect the reactive transport of CO2 during injection into saline aquifers. A compositional simulation model was created, wherein CO2 is injected for 25 years, followed by a 3000-year shut-in period. Various parameters, including CO2 plume migration, changes in pH, water density variations, mineral dissolution and precipitation, and porosity changes in the reservoir rock, are examined to understand the complex CO2–brine–rock interactions. The effect of formation mineralogy on CO2 trapping mechanisms was investigated. To do so, a sensitivity study was conducted and then, special cases with extreme mineral concentrations were studied. The simulation results highlight the profound effects of different minerals on the CO2 trapping mechanisms. Quartz exhibits minimal dissolution, while calcite plays a crucial role, initially dissolving due to low pH and later precipitating after around 300 years. Anorthite dissolution provides ions for kaolinite precipitation, and the release of calcium ions from anorthite dissolution contributes to carbonate minerals precipitation. Porosity changes in the reservoir rock are observed, with regions experiencing an increase due to early calcite dissolution and subsequent changes associated with mineral precipitation. Sensitivity analysis showed that Anorthite and Illite facilitate more CO2 mineralization, with Anorthite and Illite showing 0.68 and 0.46 correlation with mineral trapping, respectively. Conversely, minerals like Calcite and Kaolinite positively correlated with CO2 solubility, with correlations of + 0.21 and + 0.23 respectively, without significantly promoting its conversion into mineral forms, while Quartz, K-Feldspar, and Dolomite show minor effects on CO2 trapping mechanisms. Elevating Anorthite concentrations speeds up CO2 mineralization, ensuring secure storage in saline aquifers, with a minimum threshold concentration of 0.05 volume fraction; beyond this point, no further changes in CO2 mineralization are observed. Formation brine salinity significantly affects CO2 solubility and, consequently, mineral trapping, as higher salinity levels hinder CO2 dissolution and restrict its availability for geochemical reactions with rock minerals. This study offers insights that can inform reservoir characterization and management practices, ultimately enhancing the effectiveness of carbon sequestration efforts.
Rezk, M & Ibrahim, A. (2025) Impact of Rock Mineralogy on Reactive Transport of CO2 during Carbon Sequestration in a Saline Aquifer. Journal of Petroleum Exploration and Production Technology.
Read the full paper here: Impact of Rock Mineralogy on Reactive Transport of CO2 during Carbon Sequestration in a Saline Aquifer I Journal of Petroleum Exploration and Production Technology.
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Carbon Dioxide Removal Dilemma of Macroalgae Products: Evidence from Carbon Footprint and Profitability
Abstract:
Macroalgae can bio-sequester atmospheric CO2 into their biomass, thus it has been proposed and debated as a viable carbon dioxide removal strategy to mitigate climate change. We examine the carbon footprints of common macroalgae products through a “cradle-to-grave” life cycle assessment, and find carbon sequestration effect can only be accomplished by some specific macroalgae product types when they are properly stored rather than being used. We identify the product processing and usage stages in macroalgae’s life cycle contribute most carbon emissions, while the net primary production of macroalgae during growth only partially neutralizes its overall CO2 emissions. A sensitivity test for such life cycle model indicates employing clean energy and improving technical efficiency can potentially achieve net-zero for some macroalgae products e.g., biochar. However, even considering macroalgae’s ecological values, our profitability investigation concludes that macroalgae products for carbon sequestration are extremely unattractive to practitioners under current carbon pricing level.
Jiao, T., Feng, E., Li, Y, & Tian, Y. (2025) Carbon Dioxide Removal Dilemma of Macroalgae Products: Evidence from Carbon Footprint and Profitability. Journal of Cleaner Production.
Read the full paper here: Carbon Dioxide Removal Dilemma of Macroalgae Products: Evidence from Carbon Footprint and Profitability I Journal of Cleaner Production.
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Polyethyleneimine-Functionalized Graphene Oxide Aerogels for Direct Air Capture
Abstract:
Amine-functionalized sorbents are promising materials for direct air capture (DAC). Reduced graphene oxide (rGO) aerogels have higher electrical and heat conductivities than commonly studied aminated silica. These properties could jointly enhance the productivity of an associated CO2 separation process. In this study, three-dimensional (3D) rGO aerogels were fabricated, modified with polyethyleneimine (PEI) at various mass ratios, and applied successfully as a CO2 adsorbent at different temperatures and pressures. The structure, morphology, and chemical properties of the aminated composite aerogels based on PEI-rGO were comparably characterized using elemental analysis, thermogravimetric analysis, and scanning electron microscopy. The CO2 uptake performance of the PEI-rGO aerogels was assessed by analysis of the adsorption isotherms at 20 and 50 °C. The optimized PEI-rGO-71 (referring to 71 wt% PEI to the sample) exhibited the highest CO2 uptake across the tested CO2 pressure range (0.03–101 kPa), reaching 0.61 mmol CO2/g at the partial pressure of CO2 in ambient air (0.04 kPa). It showed a superior CO2 capture capacity compared to previously reported amine-modified graphene-based sorbents at ambient CO2 concentration.
Ai, J., Bacsik, Z., Hallstensson, K., Yuan, J., Sugunan, A. & Hedin, N. (2025) Polyethyleneimine-Functionalized Graphene Oxide Aerogels for Direct Air Capture. Chemical Engineering Journal.
Read the full paper here: Polyethyleneimine-Functionalized Graphene Oxide Aerogels for Direct Air Capture I Chemical Engineering Journal.