Carbon Removal Research Articles

Enhanced Rock Weathering for Carbon Removal-Monitoring and Mitigating Potential Environmental Impacts on Agricultural Land.

Terrestrial enhanced rock weathering (ERW) is the application of pulverized silicate rock to soils for the purposes of carbon removal and improved soil health. Although a geochemical modeling framework for ERW in soils is emerging, there is a scarcity of experimental and field trial data exploring potential environmental impacts, risks, and monitoring strategies associated with this practice. This paper identifies potential negative consequences and positive cobenefits of ERW scale-up and suggests mitigation and monitoring strategies. To do so, we examined literature on not only ERW but also industry, agriculture, ecosystem science, water chemistry, and human health. From this work, we develop recommendations for future research, infrastructure, and policy needs. We also recommend target metrics, risk mitigation strategies, and best practices for monitoring that will permit early detection and prevention of negative environmental impacts.

Ag doped TiO2 anchored on metal free g-C3N4 for enhanced solar light activated photodegradation of a dye

Heterogeneous semiconductor photocatalysis has attracted researcher's attention in wastewater treatment owing to the improved surface area, optical properties, and charge transfer rate for boosted degradation of organic pollutants. Thus, the g-C3N4/Ag/TiO2 was prepared following a hydrothermal route for the degradation of azo dye tartrazine (TA) used as a food colourant under solar light. Before application, the composite and pristine materials were interrogated for physicochemical and structural properties using SEM, TEM, EDS, XPS, XRD, UV–vis DRS, PL, BET, Raman, and FTIR spectroscopy. The PL and electrochemical analysis revealed that the CNAT composite had a high charge transfer rate that was coupled with low charge carrier complexation. The degradation efficiency of 91 % was realized in 180 min and the rate of pseudo-first-order kinetics of 0.01143 min−1 was obtained. The CNAT catalyst also displayed high removal efficiency towards a cocktail of naproxen (NPX) and TA. The improved removal efficiencies stem from increased visible usage, reduced charge carrier compounding, and formation of Z-scheme heterojunction with high redox capabilities. The total organic carbon removal reached 95 % while CNAT showed high convincing stability even after four cycles. Given the above results, the hydrothermally prepared composite catalyst can be extended to other organic pollutants such as pharmaceuticals, pesticides, and reduction of inorganics.

Photo-Fenton Treatment under UV and Vis Light Reduces Pollution and Toxicity in Water from Madín Dam, Mexico

Water from Madín Dam in Mexico has been shown to contain a wide variety of pollutants such as drugs, pesticides, personal care products and compounds that are released into the environment as waste from production processes. In this work, the effect of the main process variables on the percentage of total organic carbon (TOC) removal in water samples from the Madín reservoir was studied by applying a photo-Fenton treatment catalyzed with iron-pillared clays. The catalyst was characterized by XRD, N2 physisorption, DRS and XPS. The sampling and characterization of the water from the Madín reservoir was carried out according to Mexican standards. The system for treatment tests was 0.1 L of reaction volume and a controlled temperature of 23–25 °C, and the reaction system was kept under constant stirring. After 4 h of treatment time under UV light, the TOC removal was 90%, and it was 60% under Vis light. The main ROS involved in the photo-Fenton process driven by UVC light were hydroxyl radicals, while hydroperoxyl radicals predominate in the Vis-light-driven process. Evidence of superoxide anion participation was not found. The toxicity of untreated and treated water was assessed on Danio rerio specimens, and it was observed to be reduced after the photo-Fenton treatment.

Nordic perspectives on the emerging biochar business

Biochar production offers various benefits related to climate change mitigation, circular economy, waste management, renewable energy, and reduced dependency on fossil carbon. Despite these advantages, the biochar market in the Nordic region is still developing. This study explores the current state and future potential of the Nordic biochar market, identifying existing and potential market segments, the role of biochar and its co-products, and factors affecting market growth. The study involved an online survey conducted in 2021, targeting key Nordic biochar stakeholders, including business actors, academic researchers, and other relevant groups (N = 72, representing 64 organizations). The findings reveal that the Nordic biochar market is in its nascent stages, with producers often considering biochar production as a side business. The market faces challenges such as inadequate legal and policy support, limited public awareness, lack of established norms, and uncertainties regarding profitability, technological efficiency, and market potential. However, the industry holds substantial growth potential due to its environmental and climate benefits, provided that current barriers are overcome. Key applications of biochar include carbon removal, water filtration, soil remediation, landscaping, and composting. Additionally, co-products such as energy-dense gases and bio-oil have the potential to enhance the economic viability of biochar production. To facilitate market development, integrating established scientific knowledge into industry standards and policies is crucial. The study underscores the importance of biochar networks and associations in advocating for industry development and highlights the need for enhanced collaboration among stakeholders to overcome existing barriers. Additionally, focused research on the varied applications of biochar is needed, with an emphasis on thoroughly evaluating its environmental, economic, and social impacts.

Fabrication of a novel microflower BiOCl composite incorporated with rosemary powder for enhanced oxygen vacancies and visible-light photocatalytic efficiency

Incorporating metallic or nonmetallic compounds is a promising method for enhancing the oxygen vacancies (OVs), charge transport, and visible light absorption of a bismuth oxychloride (BiOCl) semiconductor. This research aims to improve the properties of BiOCl by incorporating rosemary powder (RPC). BiOCl photocatalysts with enhanced OVs were synthesized through the addition of 1–4 wt% of RPC using a one-pot solvothermal process. The addition of 3 % RPC resulted in the formation of very small particles on the BiOCl lamellar structures, which were aligned with the (002) plane of carbon quantum dots (CQDs). The uniformly distributed CQDs transformed the BiOCl microstructure from a two-dimensional lamellar structure to a three-dimensional floral structure, leading to an increased surface area and pore volume. The incorporation of RPC enhanced the visible light absorption capacity of BiOCl. The carbon atoms in RPC readily attach to oxygen atoms in the Bi-O bond, disrupting the Bi-O lattice bond and forming OVs. The addition of RPC contributed to a higher number of OVs, which impacted both the energy difference between the valence and conduction bands and their locations. This resulted in better charge transfer and enhanced active species formation. The 3 %-RPC-BOC photocatalyst had the highest efficiency, achieving a 98 % degradation of rhodamine B (RhB) and a 45 % removal of organic carbon within 48 min under visible light. This composite also had excellent stability and reusability, as its crystal structure remained unaltered even after conducting 7 cycles. The primary active species of 3 %-RPC-BOC system is the superoxide radical (·O2-), while the hydroxyl radical (·OH) and hole (h+) operate as minor active species. Additionally, the 3 %-RPC-BOC achieved a high tetracycline (TC) removal rate of 82.1 %, which is 2.21 times higher than that of pure BiOCl.

Green and Reflux method synthesis of CeO2/rGO for their characterization and Photodegradation of dye

In this study, cerium oxide (CeO2) was synthesized using a green and eco-friendly solution combustion method with lemongrass as the fuel source. The synthesis process was simple and environmentally friendly, leveraging a straightforward reflux technique to prepare the CeO2/rGO composite. The resulting CeO2 and CeO2/rGO composite was characterized using various analytical techniques, including XRD, FE-SEM, FTIR, EDX, UV-Vis, XPS, and BET analysis. The photocatalytic performance of the CeO2/rGO composite was evaluated through the degradation of Methyl Violet (MV) dye, demonstrating a remarkable photocatalytic efficiency with approximately 99 % degradation following a first-order reaction kinetics. The half-life period (t₁/₂) of the degradation process was determined to be 19.01 minutes, and the rate constant (k) was calculated to be 0.03971 min⁻¹. The study also explored various factors affecting the photocatalytic activity, including pH levels, dye concentration, light source, and the amount of catalyst used. Additionally, scavenger studies were performed to identify the reactive species involved, and the total organic carbon (TOC) removal efficiency was evaluated. The reusability of the CeO2/rGO catalyst was also investigated, demonstrating its potential for sustainable and effective application in environmental remediation processes.

Enhanced Photocatalytic Ozonation Using Modified TiO2 With Designed Nucleophilic and Electrophilic Sites.

Photocatalytic ozonation is considered to be a promising approach for the treatment of refractory organic pollutants, but the design of efficient catalyst remains a challenge. Surface modification provides a potential strategy to improve the activity of photocatalytic ozonation. In this work, density functional theory (DFT) calculations were first performed to check the interaction between O3 and TiO2-OH (surface hydroxylated TiO2) or TiO2-F (surface fluorinated TiO2), and the results suggest that TiO2-OH displays better O3 adsorption and activation than does TiO2-F, which is confirmed by experimental results. The surface hydroxyl groups greatly promote the O3 activation, which is beneficial for the generation of reactive oxygen species (ROS). Importantly, TiO2-OH displays better performance towards pollutants (such as berberine hydrochloride) removal than does TiO2-F and most reported ozonation photocatalysts. The total organic carbon (TOC) removal efficiency reaches 84.4 % within two hours. This work highlights the effect of surface hydroxylation on photocatalytic ozonation and provides ideas for the design of efficient photocatalytic ozonation catalysts.

Metrics for quantifying the efficiency of atmospheric CO2 reduction by marine carbon dioxide removal (mCDR)

Abstract Marine carbon dioxide removal (mCDR) is gaining interest as a tool to meet global climate goals. Because the response of the ocean–atmosphere system to mCDR takes years to centuries, modeling is required to assess the impact of mCDR on atmospheric CO2 reduction. Here, we use a coupled ocean–atmosphere model to quantify the atmospheric CO2 reduction in response to a CDR perturbation. We define two metrics to characterize the atmospheric CO2 response to both instantaneous ocean alkalinity enhancement (OAE) and direct air capture (DAC): the cumulative additionality (α) measures the reduction in atmospheric CO2 relative to the magnitude of the CDR perturbation, while the relative efficiency (ϵ) quantifies the cumulative additionality of mCDR relative to that of DAC. For DAC, α is 100% immediately following CDR deployment, but declines to roughly 50% by 100 years post-deployment as the ocean degasses CO2 in response to the removal of carbon from the atmosphere. For instantaneous OAE, α is zero initially and reaches a maximum of 40%–90% several years to decades later, depending on regional CO2 equilibration rates and ocean circulation processes. The global mean ϵ approaches 100% after 40 years, showing that instantaneous OAE is nearly as effective as DAC after several decades. However, there are significant geographic variations, with ϵ approaching 100% most rapidly in the low latitudes while ϵ stays well under 100% for decades to centuries near deep and intermediate water formation sites. These metrics provide a quantitative framework for evaluating sequestration timescales and carbon market valuation that can be applied to any mCDR strategy.

A method for siting adsorption-based direct air carbon capture and storage plants for maximum CO2 removal

Adsorption-based direct air carbon capture and storage (DACCS) is an emerging approach to mitigate climate change by removing CO2 from the atmosphere. Recent studies show separately that thermodynamic and environmental performance strongly depend on regional ambient conditions and energy supply but neglect regional CO2 storage potentials. To assess DACCS performance holistically, a detailed global analysis is needed that accounts for the interplay of regional ambient conditions, energy supply, and CO2 storage potential. Hence, we present a novel method for the optimal siting of DACCS plants derived from optimising a dynamic process model that uses global hourly weather data and regionalised data on electricity supply and CO2 storage potential. The carbon removal rate (CRR) measures the climate benefit and describes the speed at which a DACCS plant generates net negative emissions. First, we assume that CO2 storage is possible everywhere. For four electricity supply scenarios, we show that the optimal siting of DACCS significantly increases the CRR when comparing the best and worst locations in each scenario: For a DACCS plant with a nameplate capture capacity of 4 kt CO2 y−1, the CRR can be increased by 63% from 2.16 to 3.53 kt CO2 y‑1 when using photovoltaic, and by 39% from 2.95 to 4.1 kt CO2 y‑1 when using wind power. Assuming a carbon-free electricity supply, the CRR varies between 3.17 and 4.17 kt CO2 y‑1 (32%). Second, we significantly narrow down optimal locations for DACCS considering regional CO2 storage potential through CO2 mineralisation. Overall, accounting for the interplay of regional DAC performance, energy supply, and CO2 storage potential can significantly improve DACCS siting.

Techno-economic analysis of geothermal combined with direct and biomass-based carbon dioxide removal for high-temperature hydrothermal systems

Limiting global temperature rise to between 1.5 and 2 °C will likely require widespread deployment of carbon dioxide removal (CDR) to offset sectors with hard-to-abate emissions. As financial resources for decarbonization are finite, strategic deployment of CDR technologies is essential for maximizing atmospheric CO2 reductions. Carbon capture and sequestration (CCS), using either direct air capture (DACCS) or bioenergy (BECCS) technologies has a particular synergy with geothermal electricity generation. This is because expensive geothermal infrastructure can be leveraged to transport dissolved CO2 for storage in subsurface reservoirs.Here, we present a techno-economic comparison of renewable electricity generation coupled with either BECCS or DACCS at high-temperature, low-gas hydrothermal systems. We use a systems model that quantifies energy, carbon and financial flows through a generic hybrid power plant. At a CO2 market price of $100/tonne, the geothermal-BECCS system has a lower median cost of electricity generation ($88/MWh) than geothermal-DACCS ($181/MWh) and conventional geothermal ($89/MWh).Geothermal-BECCS also had the lowest costs of overall emissions abatement, $122/tCO2, accounting for carbon removal and assuming displacement of fossil-fuel generation. Abatement costs are even lower, $45/tCO2, for BECCS retrofit of existing geothermal plants, owing to discounted costs of pre-existing injection wells, steam fields, and plant equipment.For a case study based on a geothermal field in New Zealand's Taupō Volcanic Zone (TVZ), we determined that achieving CDR rates of 1 MtCO2/year via new geothermal-BECCS builds would require 62 standard geothermal wells and 790 kt/year of feedstock and result in 511 MWe in installed capacity. In contrast, geothermal-DACCS would need 49 wells and no external fuel source to achieve 1 MtCO2/year scale but result in only 190 MWe in installed capacity. Both pathways are calculated to require similar upfront investment costs at $2.2 billion and $2.3 billion for geothermal-BECCS and geothermal-DACCS respectively.Although geothermal-DACCS removes CO2 at high rates, its high parasitic load increases the overall decarbonization cost ($187/tCO2). In contrast, when biomass hybridization is considered, geothermal-BECCS has a lower cost of emissions abatement and produces 20 % more electricity than the benchmark geothermal plant. We conclude that this increase in electricity production makes geothermal-BECCS the more cost-effective geothermal-based CDR configuration. Finally, we argue that revenues from net-negative CO2 emissions and increased power production make geothermal-CDR a cost-competitive decarbonization technology.

Activation of iron oxides through organic matter-induced dissolved oxygen penetration depth dynamics enhances iron-cycling driven ammonium oxidation in microaerobic granular sludge

The iron redox cycle can enhance anammox in treating low-strength ammonia wastewater. However, maintaining an effective iron redox cycle and suppressing nitrite-oxidizing bacteria in a one-stage partial nitritation and anammox (PN/A) process poses challenges during long-term aeration. We proposed a novel and simple strategy to achieve an efficient iron redox cycle in an iron-mediated anoxic-microaerobic (A/O) process by controlling organic matter (OM) at medium-strength levels (30–110 mg COD/L) in microaerobic granular sludge (MGS)-dominated reactor. The developed A/O process consistently achieved >90 % OM removal and >75 % nitrogen removal. Medium-strength OM varied the penetration depths of dissolved oxygen (DO) in MGS, regulating redox conditions and promoting redox reactions across MGS layers, thus activating accumulated inert iron oxides. Ammonia-oxidizing bacteria (Nitrosomonas), iron-reducing bacteria (e.g., Ignavibacterium, Geobacter), and anammox bacteria (Ca. Kuenenia) coexisted harmoniously in MGS. This coexistence ensured high anammox and Feammox rates along with a robust iron redox cycle, thereby mitigating the adverse impacts of fluctuating DO and OM on one-stage PN/A process stability. The identification of iron reduction-associated genes within Ca. Kuenenia, Ignavibacterium, and Geobacter suggests their potential roles in supporting Feammox coupled in one-stage PN/A process. This study introduces an iron-cycle-driven A/O process as an energy-efficient alternative for simultaneous carbon and nitrogen removal from low-strength wastewater.

Modification of polyethylene for oil-water separation in industrial wastewater treatment

Low-density polyethylene (LDPE) is extensively used worldwide in various applications due to its versatile features and abundant commercial availability. This study investigated, for the first time, the beneficial use of a novel chemically modified commercial-grade LDPE as a sorbent for oil-water separation in industrial wastewater treatment. Several laboratory tests were conducted in batch and continuous fixed-bed modes to evaluate the LDPE adsorbent’s capacity, performance repeatability and recyclability under relevant field conditions. These results were compared to walnut shell (WS), a widely used sorbent for removing oil from industrial wastewaters, including produced water from oil and gas operations. Untreated LDPE achieved higher total organic carbon (TOC) removals and retention capacities, ∼20 % and ∼66 mg/g, respectively, when compared to untreated WS, <5 % and <1 mg/g, respectively. Improved kinetics and adsorption behavior favorability were achieved for LDPE after chemical modification using a cationic monomer. Both the chemically treated LDPE and WS showed comparable TOC removal rates (ranging from 60 % to 80 %). However, the modified LDPE exhibited higher sorption capacities (∼61 mg/g) compared to the treated WS (8.0 mg/g). Chemical regeneration of LDPE with toluene demonstrated superior performance recovery (>90 %) when compared to physical cleaning with deionized water (<40 %). The study presented promising results in advancing novel materials like LDPE to support circular economy in industrial wastewater treatment.

Anchoring Ni(II) bisacetylacetonate complex into CuS immobilized MOF for enhanced removal of tinidazole and metronidazole

Here in this study, a novel ternary CuS/HKUST‒1/Ni(acac)2 nano photocatalyst (CSHK‒Ni) was developed through a facile modification of HKUST‒1 MOF with Ni(acac)2 metal complex and by immobilizing CuS into the metal-organic framework (MOF). The incorporation of CuS, a narrow bandgap semiconductor, is anticipated to allow easy excitation by visible-light and improve the photocatalytic potential of the formulated catalyst which is validated by the decrease in the bandgap energy from 3.10 eV of pristine MOF to 2.19 eV. Moreover, the anchoring of the metal complex improves the light harvesting behavior by increased conjugation. Photoluminescence studies provided evidence of the effective separation of the photoinduced charge-carriers, reducing the rate of recombination and enhancing the photocatalytic potential of the CSHK‒Ni nanocomposite. The engineered catalyst displayed remarkable efficiency in the degradation of nitroimidazole containing antibiotics, Tinidazole (TNZ) and Metronidazole (MTZ), via H2O2 assisted AOP achieving a maximum photocatalytic efficiency of 95.87 ± 1.64% and 97.95 ± 1.33% in just 30 min under irradiation of visible light at optimum reaction conditions. The possible degradation pathway was elucidated based on the identification of ROS and degradation intermediates via HR‒LCMS and quenching experiments. Meanwhile, the chemical oxygen demand (COD) and total organic carbon (TOC) removal were also examined, encompassing the discussing of various aspects including reaction conditions, influence of various oxidizing agents, competing species and dissolved organic substrates present in the wastewater, marking the novelty of the study. This research elucidated the role of the CSHK‒Ni nanocomposite as an interesting photocatalyst in the elimination of emerging nitroimidazole containing pharmaceutical pollutant under visible-light exposure, presenting an exciting novel avenue for a cleaner and greener environment in the days to come.

Integrating machine learning with experimental investigation for optimizing photocatalytic degradation of Rhodamine B using neodymium-doped titanium dioxide: a comprehensive approach with toxicity assessment.

In this study, neodymium-doped titanium dioxide (Nd-TiO2) nanoparticles were synthesized via a hydrothermal method for the photocatalytic degradation of Rhodamine B (RhB) under UV and sunlight conditions. The properties of these NPs were comprehensively characterized. And optimization of RhB degradation was conducted using control-variable experiment and artificial neural networks (ANN) under various operational conditions and in the presence of competing compounds. The acute toxicity of both NPs, RhB, and the environmental impact of the photocatalytic treatment effluent on Danio rerio were evaluated. The Nd modification increased the catalyst's specific surface area and thermal stability. X-ray diffraction confirmed the tetragonal anatase phase in undoped TiO2, while Nd-doped TiO2 exhibited shifts in peaks and the presence of brookite and rutile phases. Nd (1mol%) doped TiO2 demonstrated superior RhB photocatalytic degradation efficiency, achieving 95% degradation and 82% total organic carbon (TOC) removal within 60min under UV irradiation. Optimization under sunlight conditions yielded 95.14% RhB removal with 0.28g/L photocatalyst and 1% doping. Under UV light, 98.12% RhB removal was optimized with 0.97% doping, along with the presence of humic acid and CaCl2. ANN modeling achieved high precision (R2 of 0.99) in modeling environmental photocatalysis. Toxicity assessments indicated that the 96-h LC50 values were 681.59mg L-1 for both NPs, and 23.02mg L-1 for RhB. The treated dye solution exhibited a significant decline in toxicity, emphasizing the potential of 1% Nd-TiO2 in wastewater treatment.

Surface modification effects on ammonium perchlorate wettability

Solid propellants are commonly used for propulsion systems due to their high volumetric thrust and reliability. Powder bed, binder jetting manufactured propellants will enable unique geometries to be made that are necessary for designers to achieve high thrust levels. However, changes to the particulate wettability from the solvent-based manufacturing technique must be understood such that propellants with adequate mechanical properties are achieved. In this work, the wettability of ammonium perchlorate (AP) crystal surfaces is quantified with solvent and air plasma treatments. Removal of adventitious carbon from AP surface decreases the polybutadiene contact angle from 34 ± 1° to 15 ± 4°. The presence of hydrocarbons from non-polar solvents used in this study with lower vapor pressure was observed to have a similar effect as the adventitious carbon whereas higher vapor pressure solvents have minimal influence on the final wettability of AP surfaces. Polar solvents were determined to alter the surface topology by creating a more hydrophobic surface when compared to the plasma treated samples. An increase in concentration of amine surface groups overcomes the decrease in wettability from carbonaceous residue and surface morphology. The extension and implications of these findings to powder bed, binder jetting manufacturing for propellants is discussed.

Removal of metals and assimilable organic carbon by activated carbon and reverse osmosis point-of-use water filtration systems

Activated carbon (AC) systems and reverse osmosis (RO) systems are commonly used point-of-use (POU) water filtration systems for removing trace-level contaminants in tap water to protect human health. However, limited research has been done to evaluate their effectiveness in removing heavy metals like manganese (Mn) and uranium (U), or to assess the potential for undesired microbial growth within POU systems, which can reduce their treatment efficiency. This study aimed to systematically evaluate the removal of metals and assimilable organic carbon (AOC) in POU systems. AC systems were operated to 200% of their designed treatment capacities and RO systems were run for three weeks. The results showed that AC systems were generally ineffective at removing metals from drinking water, while RO systems effectively removed them. Both Mn and U were poorly removed by AC systems. Calcium (Ca) and magnesium (Mg) were poorly removed by AC systems, with efficiencies of less than 1%. Iron (Fe) removal by AC systems varied between 61% and 84%. Copper (Fe), likely due to its low influent concentration (<30 μg L−1), was effectively removed by AC systems with efficiencies over 95%. In contrast, RO systems consistently removed all metals effectively. Mn and U removal in RO systems exceeded 95%, while Ca, Mn, Fe, and Cu were all removed with efficiencies greater than 98%. AOC was effectively removed from all AC and RO systems, but with high variability in removal efficiency, which is likely attributed to the heterogeneity of biofilm and microbial growth within the POU systems. The new knowledge generated from this study can improve our understanding of chemical contaminant removal in POU systems and inform the development of better strategies for designing and operating POU systems to remove chemical contaminants in drinking water and mitigate their associated health risks.

RUSSELL REVIEW Soil carbon stewardship: Thinking in circles

AbstractThe words we choose to describe our research ultimately directs its course. A dominant term in soil science now, is ‘sequestration’, referring to the removal of carbon (C) from air and its irreversible seclusion in soil, ideally as stable soil organic carbon (SOC). An emerging view, however, now sees SOC as an inherently dynamic assemblage of forms, all potentially vulnerable to decay, with no discrete, measurable fraction holding C in ‘sequestered’ form. Rather than speaking of C ‘sequestration’, then, we might refer instead to SOC ‘stewardship’. This word, now, enfolds the entire spectrum of SOC, not merely some elusive ‘persistent’ or ‘stable’ fraction, perhaps redirecting inquiry; for example, does C need to be ‘sequestered’ in stable form for SOC to serve as effective repository of excess atmospheric CO2? ‘Stewardship’ explicitly accepts the relentless turnover of SOC, emphasizing the need to manage not only fixed stocks of C, but also the cyclical flows of C through ecosystems that drive their functions. Among other benefits, ‘stewardship’ might motivate us to consider all functions of SOC (not only climate mitigation), consider the entire C cycle (not only enhancing soil C), and preserve existing troves of SOC (not only augmenting them in selected places.) Perhaps most fundamentally, by its etymology, ‘stewardship’ poses a compelling, timeless question: for whom do we steward SOC? Asking why look after SOC, not only reflects our own underlying quest for resilience, but also expands our potential audience and entices the more creative minds that must succeed us. Although ‘stewardship’ may elicit new and fruitful inquiry, we may need to look for words even more evocative, more alluring, more true to our mandate of living well within the circling C that must always sustain us.

Optimizing sustainable development in arid river basins: A multi-objective approach to balancing water, energy, economy, carbon and ecology nexus

The ongoing water crisis poses significant threats to the socioeconomic sustainability and ecological security of arid and semi-arid river basins. Achieving Sustainable Development Goals (SDGs) within a complex socio-ecological nexus requires effective and balanced resource management. However, due to the intricate interactions between human societies and environmental systems, the tradeoffs and synergies of different SDGs remain unclear, posing a substantial challenge for collaborative management of natural resources. Here we introduce a gray fractional multi-objective optimization (GFMOP) model to balance multi-dimensional SDGs through a novel water–energy–economy–carbon–ecology nexus perspective. The model was applied to a typical arid river basin in Northwest China, where thirty-two scenarios were explored, considering factors such as shared socioeconomic pathways, carbon removal rates, water conveyance efficiencies, and ecological requirements. The results reveal a strong tradeoff between marginal benefit and carbon emission intensity, indicating that improving the economic efficiency of water use can simultaneously reduce emissions and protect the environment. Given the immense power generation potential, wind power development should be prioritized in the future, with its share in the energy structure projected to increase to 23.3% by 2060. Furthermore, promoting carbon capture technologies and expanding grassland coverage are recommended to achieve regional carbon neutrality, contributing 39.5% and 49.1% to carbon absorption during 2021–2060, respectively. Compared with traditional single-objective models, GFMOP demonstrates a superiority in uncovering interrelationships among multiple SDGs and identifying compromised alternatives within the compound socio-ecological nexus. The model also provides detailed strategies for resource allocation and pollutant control, offering valuable guidance to policymakers and stakeholders in pursuing sustainable and harmonious watershed management.

Utilizing MXene-mediated electron transfer pathway to boost peroxymonosulfate activation for water purification

Regulating the performance of manganese oxide catalysts to enhance peroxymonosulfate (PMS) activation for degrading emerging organic pollutants remains a significant challenge. To address this issue, Mn3O4/MXene composites with precisely controlled MXene contents are synthesized by combining hydrothermal and calcining methods, resulting in a significant regulate the pathway of Mn3O4 activation of PMS and a notable enhancement bisphenol A (BPA) degradation efficiency. The normalized first-order rate constant for optimized Mn3O4/MXene composites is 0.0218 g/(m2⋅min), which is 8.4 and 2.0 times higher than those of MXene and Mn3O4, respectively. Moreover, this catalyst exhibits excellent mineralization capacities, achieving up to 88.2 % total organic carbon removal efficiency. Combining with electrochemical and electron paramagnetic resonance analysis, the mechanism of electron transfer processes in this composite is elucidated comprehensively. Moreover, Mn3O4/MXene displays remarkable efficiency in degrading refractory pollutants, including antibiotics, phenols, and dyes. Furthermore, Mn3O4/MXene composites exhibit superior stability, reusability, and resistance to interference, highlighting their versatility in diverse environmental contexts. Notably, the catalyst maintains stable catalytic activity for long-term pollutant removal in a continuous-flow system. This study presents a novel approach for developing composite catalysts, providing new avenues for the treatment of emerging pollutants in wastewater.

Self-regenerative Ni/SiO2 for dry reforming of methane (DRM): 1000 h-longevity assessment and operando insights to coke removal under N2 atmosphere

Commercializing Ni-catalyst for dry reforming of methane (DRM) has yet to be realized due to two known issues: catalyst sintering and carbon deposition. Significantly, our developed tremella-like Ni/SiO2 has previously demonstrated outstanding resilience against sintering under prolonged heat exposure. The carry-on investigation herein further showcases its interesting self-regenerative behavior, which enables carbon removal and full activity restoration under inert N2-blanket. Better still, the resultant N2-regenerated Ni/SiO2 can immediately re-apply to DRM, contrasted to the traditional oxidative-regenerated counterpart that mandated intermediate reduction process for catalyst re-activation. Characterization results indicate that an appreciable portion (32.05 %) of deposited Ni (7.3 wt%) is reducible into active metallic phase; however, only 1.233 % of them are resided on the surface of Ni/SiO2 and involved in DRM. Despite such low involvement rate, >90 % CO2 and CH4 conversion could still be attained initially, reasonably due to the morphological prominence of the catalyst. Longevity experiment confirmed the adequacy of intermittent N2-regeneration in removing deposited carbonaceous, mechanistically assisted by the labile O-atom migrated from SiO2 support. Upon 4 h N2-regeneration, thorough activity restoration of Ni/SiO2 can be facilely realized, thereafter sustaining DRM for 1000 h with CO2 conversion controlled at > 78 %. The results herein provide important insights to DRM community, where the demonstrated N2-self-regeneration process promises a reduction-free, time- and cost-saving solution to DRM catalysts beyond Ni/SiO2.