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1. Self‐Regenerative Ni‐Doped CaTiO ₃ /CaO for Integrated CO ₂ Capture and Dry Reforming of Methane

   https://doi.org/10.1002/smll.202401156  

   Jo, Seongbin; Gilliard‐AbdulAziz, Kandis Leslie (April 2024, Small)

   Abstract In this work, a new type of multifunctional materials (MFMs) called self‐regenerative Ni‐doped CaTiO₃/CaO is introduced for the integrated CO₂capture and dry reforming of methane (ICCDRM). These materials consist of a catalytically active Ni‐doped CaTiO₃and a CO₂sorbent, CaO. The article proposes a concept where the Ni catalyst can be regenerated in situ, which is crucial for ICCDRM. Exsolved Ni nanoparticles are evenly distributed on the surface of CaTiO₃under H₂or CH₄, and are re‐dispersed back into the CaTiO₃lattice under CO₂. The Ni‐doped CaTiO₃/CaO MFMs show stable CO₂capture capacity and syngas productivity for 30 cycles of ICCDRM. The presence of CaTiO₃between CaO grains prevents CaO/CaCO₃thermal sintering during carbonation and decarbonation. Moreover, the strong interaction of CaTiO₃with exsolved Ni mitigates severe accumulation of coke deposition. This concept can be useful for developing MFMs with improved properties that can advance integrated carbon capture and conversion. 

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2. New insights into the mechanisms of carbon dioxide mineralization by portlandite

   https://doi.org/10.1002/aic.17160  

   Falzone, Gabriel; Mehdipour, Iman; Neithalath, Narayanan; Bauchy, Mathieu; Simonetti, Dante; Sant, Gaurav (January 2021, AIChE Journal)

   Abstract Portlandite (Ca(OH)₂; also known as calcium hydroxide or hydrated lime), an archetypal alkaline solid, interacts with carbon dioxide (CO₂) via a classic acid–base “carbonation” reaction to produce a salt (calcium carbonate: CaCO₃) that functions as a low‐carbon cementation agent, and water. Herein, we revisit the effects of reaction temperature, relative humidity (RH), and CO₂concentration on the carbonation of portlandite in the form of finely divided particulates and compacted monoliths. Special focus is paid to uncover the influences of the moisture state (i.e., the presence of adsorbed and/or liquid water), moisture content and the surface area‐to‐volume ratio (s_a/v, mm⁻¹) of reactants on the extent of carbonation. In general, increasing RH more significantly impacts the rate and thermodynamics of carbonation reactions, leading to high(er) conversion regardless of prior exposure history. This mitigated the effects (if any) of allegedly denser, less porous carbonate surface layers formed at lower RH. In monolithic compacts, microstructural (i.e., mass‐transfer) constraints particularly hindered the progress of carbonation due to pore blocking by liquid water in compacts with limited surface area to volume ratios. These mechanistic insights into portlandite's carbonation inform processing routes for the production of cementation agents that seek to utilize CO₂borne in dilute (≤30 mol%) post‐combustion flue gas streams. 

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3. Balancing Non‐CO ₂ GHG Emissions and Soil Carbon Change in U.S. Rice Paddies: A Retrospective Meta‐Analysis and Agricultural Modeling Study

   https://doi.org/10.1029/2023AV001052  

   Zhang, Jingting; Tian, Hanqin; You, Yongfa; Liang, Xin‐Zhong; Ouyang, Zutao; Pan, Naiqing; Pan, Shufen (February 2024, AGU Advances)

   Abstract U.S. rice paddies, critical for food security, are increasingly contributing to non‐CO₂greenhouse gas (GHG) emissions like methane (CH₄) and nitrous oxide (N₂O). Yet, the full assessment of GHG balance, considering trade‐offs between soil organic carbon (SOC) change and non‐CO₂GHG emissions, is lacking. Integrating an improved agroecosystem model with a meta‐analysis of multiple field studies, we found that U.S. rice paddies were the rapidly growing net GHG emission sources, increased 138% from 3.7 ± 1.2 Tg CO₂eq yr⁻¹in the 1960s to 8.9 ± 2.7 Tg CO₂eq yr⁻¹in the 2010s. CH₄, as the primary contributor, accounted for 10.1 ± 2.3 Tg CO₂eq yr⁻¹in the 2010s, alongside a notable rise in N₂O emissions by 0.21 ± 0.03 Tg CO₂eq yr⁻¹. SOC change could offset 14.0% (1.45 ± 0.46 Tg CO₂eq yr⁻¹) of the climate‐warming effects of soil non‐CO₂GHG emissions in the 2010s. This escalation in net GHG emissions is linked to intensified land use, increased atmospheric CO₂, higher synthetic nitrogen fertilizer and manure application, and climate change. However, no/reduced tillage and non‐continuous irrigation could reduce net soil GHG emissions by approximately 10% and non‐CO₂GHG emissions by about 39%, respectively. Despite the rise in net GHG emissions, the cost of achieving higher rice yields has decreased over time, with an average of 0.84 ± 0.18 kg CO₂eq ha⁻¹emitted per kilogram of rice produced in the 2010s. The study suggests the potential for significant GHG emission reductions to achieve climate‐friendly rice production in the U.S. through optimizing the ratio of synthetic N to manure fertilizer, reducing tillage, and implementing intermittent irrigation. 

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4. Mixed modifier effects on structural, mechanical, chemical, and mechanochemical properties of sodium calcium aluminosilicate glass

   https://doi.org/10.1111/jace.19319  

   Liu, Hongshen; Ogrinc, Andrew L.; Lin, Yinan; Wilkinson, Collin; Doss, Karan; Fry, Aubrey L.; Qu, Conghang; He, Hongtu; Gross, Timothy M.; Smith, Nicholas J.; et al (July 2023, Journal of the American Ceramic Society)

   Abstract Glass properties are governed by the interplay between network formers and network modifiers; for a given composition of network formers, the ratio of different cationic modifiers compensating the anionic species in the network has a profound effect, which is often nonlinear, called a mixed modifier effect (MME). We have investigated the MME of sodium (Na) and calcium (Ca) in an aluminosilicate (NCAS) glass series following the formula [Na₂O]_30−x[CaO]_x[Al₂O₃]₁₀[SiO₂]₆₀, wherex = 0, 7.5, 15, 22.5, and 30. A nonadditive trend was observed in hardness and indentation toughness, with aqueous corrosion resistance exhibiting a shift from incongruent to congruent corrosion, whereas the network structure determined by molecular dynamics simulations revealed no significant trend with composition. Additionally, the NCAS glass containing both [Na₂O] and [CaO] within an intermediate range exhibited superior resistance to wear at high humidity, a clear MME phenomenon previously only observed in soda–lime silica. 

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5. On the Theoretical CO2 Sequestration Potential of Pervious Concrete

   https://doi.org/10.3390/infrastructures4010012  

   Ellingboe, Ethan; Arehart, Jay; Srubar, Wil (March 2019, Infrastructures)

   Pervious concrete, which has recently found new applications in buildings, is both energy- and carbon-intensive to manufacture. However, similar to normal concrete, some of the initial CO2 emissions associated with pervious concrete can be sequestered through a process known as carbonation. In this work, the theoretical formulation and application of a mathematical model for estimating the carbon dioxide (CO2) sequestration potential of pervious concrete is presented. Using principles of cement and carbonation chemistry, the model related mixture proportions of pervious concretes to their theoretical in situ CO2 sequestration potential. The model was subsequently employed in a screening life cycle assessment (LCA) to quantify the percentage of recoverable CO2 emissions—namely, the ratio of in situ sequesterable CO2 to initial cradle-to-gate CO2 emissions—for common pervious concrete mixtures. Results suggest that natural carbonation can recover up to 12% of initial CO2 emissions and that CO2 sequestration potential is maximized for pervious concrete mixtures with (i) lower water-to-cement ratios, (ii) higher compressive strengths, (iii) lower porosities, and (iv) lower hydraulic conductivities. However, LCA results elucidate that mixtures with maximum CO2 sequestration potential (i.e., mixtures with high cement contents and CO2 recoverability) emit more CO2 from a net-emissions perspective, despite their enhanced in situ CO2 sequestration potential. 

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