Carbon Sequestration Strategies Research Articles

Responses of Soil Organic Carbon Fractions and Stability to Forest Conversion in the Nanling Nature Reserve, China

Studying the impact of typical vegetation types in forest conversion zones on soil organic carbon (SOC) structure and stability is crucial for developing terrestrial ecosystem carbon sequestration strategies. In this study, we selected three typical forest stands in the Nanling National Nature Reserve: a primary evergreen broad-leaved forest (BL), a secondary mixed coniferous and broad-leaved forest (ML), and a Chinese fir plantation (CL). Soil samples were collected to examine the SOC fractions and carbon pool management index (CPMI) in three forest stands. The influence of soil property factors on SOC fractions was also analyzed. The results showed that the transformation process from a BL to an ML or a CL changed the structure and stability of organic carbon by reducing the labile SOC fractions and increasing the recalcitrant carbon fraction in the soil. The higher lability index (LI) and CPMI of soils in the BL indicated better carbon accumulation and activity, making this treatment more advantageous for management strategies aimed at promoting natural forest renewal and ecological restoration. Correlation and RDA analysis revealed that the availability of soil P was a key factor limiting the variation in organic C fractions in the acidic soils of tropical forests in South China.

Investigation on methane hydrate formation behaviors in deep-sea methane seepage environments

Deep-sea cold seep is a natural phenomenon where methane leaks from the sea floor. Methane can be partially conversed through physical, chemical, and biological processes, but the excess methane that remains uncaptured escapes into the atmosphere and contributes to the greenhouse effect. Physical carbon sequestration via hydrate formation is a fast and high-energy density type of carbon sequestration; however, it has been largely overlooked. This study investigated hydrate formation in authigenic carbonate rocks through deep-sea geological surveys in cold seeps in the South China Sea. Investigations have shown that authigenic carbonate rocks can sequester carbon by blocking the methane plume from the seepage vents. This perspective provides a new physical carbon sequestration mode of carbonate rocks by observing the artificial collection of methane plumes in deep-sea seepage areas. The mode was simplified into two steps including the formation of a thin layer of planar hydrate film on carbonate rocks and a thick layer of hydrate through the stacking of bubbles under the thin film. Salinity, a key distinction between seawater and freshwater, was further investigated for its impact on the carbon sequestration mechanism. Results showed that saline ions in seawater had little impact on the thickening rate of the planar hydrate film but reduced the lateral growth rate of hydrates on the bubble by 60%. This reduction in the lateral growth rate greatly facilitated the three-dimensional growth, increased the hydrate thickness on the bubble, and improved the carbon sequestration efficiency. Hydrate formation on the exposed carbonate rock can effectively impede methane plume migration into upper water and atmosphere, mitigate the greenhouse effect, and present a promising strategy for carbon sequestration in deep-sea methane seepage areas.

An Integrated Numerical Study of CO2 Storage in Carbonate Gas Reservoirs with Chemical Interaction between CO2, Brine, and Carbonate Rock Matrix

In light of the burgeoning interest in mitigating anthropogenic CO2 emissions, carbonate reservoirs have emerged as promising sequestration sites due to their substantial storage potentials. However, the complexity of CO2 storage in carbonate reservoirs exceeds that in conventional sandstone reservoirs, predominantly due to the rapid interactions occurring between the injected CO2, brine, and carbonate rock matrix. In this study, a numerical model integrated with the chemical CO2–brine–rock matrix interaction was developed to analyze the carbonate rock dissolution process and the physical property variations of different carbonate gas reservoirs during the CO2 injection and sequestration process. More specifically, a total of twenty scenarios were simulated to examine the effects of lithology, pore size, pore–throat structures, and CO2 injection rate on carbonate rock matrix dissolution and reservoir property variation. Calcite is significantly easier and quicker to react with CO2-solvated brine than dolomite; as a result, limestones exhibit an expedited rock dissolution and pore volume increase, along with a slower pressure buildup in comparison to dolomites. Also, the carbonate reservoir with a smaller pore size has a higher rock dissolution rate than one with a larger pore size. Furthermore, the simulation results show injected CO2 can modify the pore-dominant carbonate reservoir to a more pronounced extent than the fracture-dominant carbonate reservoir. Lastly, the carbonate rock dissolution is more obvious at a lower CO2 injection rate. The insights derived from this research aid evaluations related to CO2 injectivity, storage capacity, and reservoir integrity, thereby paving the way for environmentally and structurally sound carbon sequestration strategies.

Divergent changes in particulate and mineral-associated organic carbon under natural revegetation along a soil texture gradient in temperate grasslands of China

The natural revegetation of grasslands can stimulate belowground carbon inputs and facilitate the storage of soil organic carbon (SOC), which is conducive to the restoration of grassland ecosystems. Previous studies have investigated the dynamics of organic carbon (OC) in bulk soil, but paid little attention to OC fractions within aggregates. This study explored the response of OC changes in functionally distinct fractions, namely particulate organic matter (POM) and mineral-associated organic matter (MAOM), to natural restoration through systematic measurements of two grassland vegetation species at three study sites along a soil texture gradient in the Loess Plateau. In naturally restored grasslands, the SOC and OC contents of POM (POM_C) and MAOM (MAOM_C) within bulk soil and aggregates were significantly (p < 0.05) higher relative to bare land, with more effective improvement of POM_C (1.01−6.55 times) than MAOM_C (0.88−4.26 times). Compared to cover type (6.01 %−26.04 %), soil texture explained the variance of OC fractions to a greater extent (56.39 %−88.16 %). Soil texture had a larger contribution to MAOM_C in bulk soil with standardized path coefficients for total effect of 0.78 than POM_C, which had a coefficient of 0.67 (p < 0.05). Moreover, the growth rate of the MAOM_C pool exhibited a gradual decline (p < 0.001), which subsequently approached saturation level despite a persistent increase in total SOC in both bulk soil and aggregates. During soil carbon sequestration, aggregate fractions with relatively smaller particle size reached the MAOM_C saturation more easily than fractions with larger size. The findings of this study highlight the important role of soil texture in determining the saturation level of the MAOM_C pool at the regional scale. In the development of soil carbon sequestration strategies, more attention should be paid to the divergent behaviors of different SOM fractions and their distinct responses to natural restoration at larger spatiotemporal scales.

Mapping sub-surface distribution of soil organic carbon stocks in South Africa's arid and semi-arid landscapes: Implications for land management and climate change mitigation

Soil organic carbon (SOC) stocks are critical for land management strategies and climate change mitigation. However, understanding SOC distribution in South Africa's arid and semi-arid regions remains a challenge due to data limitations, and the complex spatial and sub-surface variability in SOC stocks driven by desertification and land degradation. Thus, to support soil and land-use management practices as well as advance climate change mitigation efforts, there is an urgent need to provide more precise SOC stock estimates within South Africa's arid and semi-arid regions. Hence, this study adopted remote-sensing approaches to determine the spatial sub-surface distribution of SOC stocks and the influence of environmental co-variates at four soil depths (i.e., 0-30 cm, 30-60 cm, 60-100 cm, and 100-200 cm). Using two regression-based algorithms, i.e., Extreme Gradient Boosting (XGBoost) and Random Forest (RF), the study found the former (RMSE values ranging from 7.12 t/ha to 29.55 t/ha) to be a superior predictor of SOC in comparison to the latter (RMSE values ranging from 7.36 t/ha to 31.10 t/ha). Nonetheless, both models achieved satisfactory accuracy (R2 ≥ 0.52) for regional-scale SOC predictions at the studied soil depths. Thereafter, using a variable importance analysis, the study demonstrated the influence of climatic variables like rainfall and temperature on SOC stocks at different depths. Furthermore, the study revealed significant spatial variability in SOC stocks, and an increase in SOC stocks with soil depth. Overall, these findings enhance the understanding of SOC dynamics in South Africa's arid and semi-arid landscapes and emphasizes the importance of considering site specific topo-climatic characteristics for sustainable land management and climate change mitigation. Furthermore, the study offers valuable insights into sub-surface SOC distribution, crucial for informing carbon sequestration strategies, guiding land management practices, and informing environmental policies within arid and semi-arid environments.

Can converting raw straw into biochar incorporation achieve both higher maize yield and lower greenhouse gas emissions intensity in drought-prone environment?

Converting raw straw into biochar is considered an effective strategy for soil carbon sequestration. However, it remains uncertain whether biochar is more environmentally friendly for achieving higher crop yield in comparison to raw straw in drought-prone regions. Here, a 5-year experiment with three treatments (no incorporation(CK), raw straw incorporation(SI) and straw-derived biochar incorporation(BI)) was conducted to examine the effects of SI and BI on soil physicochemical properties, grain yield (GY), and greenhouse gas (GHG) emissions. Results indicated both SI and BI increased soil water content (SWC), soil temperature (ST), soil porosity, field capacity, pH, total nitrogen and soil organic carbon (SOC) compared with CK. On average, seasonal soil CO2 emission increased significantly by 42.3% in SI and 16.8% in BI, respectively; seasonal N2O emission increased by 26.9% in SI, while decreased by 17.5% in BI. Particularly, the 5-year average GY was as high as 9.4 t ha-1 in BI, significantly higher than that of SI and CK. The 5-year average global warming potential (GWP) increased by 57.9% and 24.6% under SI and BI, respectively, compared with CK. As a result, the average GHG emission intensity (GHGI) increased by 32.0% in SI, whereas it declined by 8.9% in BI. Attribution analysis showed that the CO2 emission primary driven GHGI change under SI, contributing up to 76.4% to GHGI increase. Conversely, the GY increase primary driven GHGI change under BI, contributing to 55.0% GHGI decrease. Therefore, converting raw straw into biochar incorporation acts as an environment-friendly strategy for higher yield harvest.

Estimation of potential carbon sequestration in Thai reforestation from mining, based on the integrated spatial analysis

Mining, an activity that dates to the earliest stages of human civilization, has played a vital role in fulfilling human requirements for an extended period of time. Nevertheless, it is worth noting that this particular activity accounts for a significant proportion, ranging from 4% to 7% of the overall world greenhouse gas emissions. These emissions mostly consist of carbon dioxide, methane, and nitrogen oxides, which are released because of fuel burning, on-site energy generation, and many other sources. The mining industry, as a constituent of industrial process and product use (IPPU) sector in Thailand, makes a substantial contribution to these emissions. Thailand is now engaged in the implementation of carbon sequestration strategies, specifically focusing on the reclamation and replanting of post-mining zones. This initiative aims to tackle the various issues associated with small-scale operations within the country’s mining sector. The objective of this study is to analyse the carbon sequestration potential of Thailand’s mining area through the utilization of satellite pictures obtained from LANDSAT 8 OLI and Geographic Information System (GIS) applications. This study assesses the present carbon storage capacity, establishes the appropriate carbon pricing, and investigates the potential for reforestation in mining areas inside the nation. Based on the findings, it is evident that the northern region of Thailand has the most substantial potential for carbon sequestration, mostly due to the presence of vegetated land. Furthermore, it is projected that the overall carbon sequestration capacity in Thailand will amount to 14.68 MtCO2e in 2023 and 28.02 MtCO2e in 2030.

Blue carbon and the role of mangroves in carbon sequestration: Its mechanisms, estimation, human impacts and conservation strategies for economic incentives

Mangroves, tidal marshes, and seagrasses have been recognized as blue carbon coastal ecosystems as they accommodate large carbon stocks, enable long-term carbon storage, have the capacity to control greenhouse gas emissions and possess the potential to reduce the rise in atmospheric CO2 levels. In the tropical and subtropical intertidal zones, mangroves show significant productivity and rapid deposition rates. Mangroves play an important role in capturing, transforming, and storing CO2 in the atmosphere into coastal sediments for a long time, displacing organic carbon from the coastal zone to the offshores and the ocean. Mangroves also help in preventing storms, hurricanes, coastal erosion, and tidal waves. Recently, mangroves have been threatened by natural and anthropogenic activities such as urbanization, pollution, aquaculture and tourism. They are expected to hamper their essential services, such as coastal defense, breeding grounds for aquatic organisms' seafood supply, etc. Despite the importance of mangrove forests in carbon sequestration and the numerous goods and services they offer humans, wood and non-wood forest products, food, fisheries, medicines, eco-tourism, and recreation. These mangrove ecosystems are deteriorating at alarming rates, necessitating immediate intervention. Thus, the protection, restoration and conservation of this ecosystem are gaining considerable attention from researchers across the globe. This paper provides information on different mangrove adaptations, their mechanisms, roles in the ecosystem, carbon estimation, influencing factors, threats, and conservation strategies for carbon sequestration in this invaluable coastal habitat.

Enhancement of CO2 Adsorption Kinetics onto Carbon by Low-Frequency High Amplitude Resonant Vibrations

Due to the excessive consumption of fossil fuels, which leads to significant greenhouse gas emissions and rapid climate change, it is crucial to develop various carbon capture and sequestration strategies. CO2 sequestration in solid, porous adsorbents like low-cost biochar has emerged as a promising approach to achieve this goal. However, slow adsorption kinetics are one of the issues that limit the widespread use of this approach. While the characteristics of the biochar are important and impact CO2 adsorption, the conditions under which adsorption occurs are equally critical. In this work, a novel strategy is proposed to accelerate the CO2 uptake rate on carbon adsorbents by utilizing Low-Frequency High Amplitude resonant vibratory mixing during the adsorption process. With this approach, the rate of adsorption (characterized by the adsorption rate constant) exhibits an increase of 46.6% and 91.3%, as calculated by two different kinetic models: the Weber and Morris model, and the Pseudo-First-Order model. Experimental observations indicate that adsorption kinetics have a mixed control between external/internal diffusion and the physisorption process. Resonant vibrations enhance system energy, promoting collisions between CO2 molecules and carbon surfaces, subsequently improving CO2 transport and surface/gas interactions, facilitating the adsorption process and thus leading to enhanced kinetic rates. Furthermore, an analysis of variance determined the sensitivity of CO2 uptake to several operating parameters associated with the resonant vibrations. This analysis indicated that the adsorption of CO2 is most sensitive to the level of fill of the adsorption vessel and the time exposed to resonant vibrations.

Molecular mechanism of dissolvable metal nanoparticles-enhanced CO2 fixation by algae: Metal-chlorophyll synthesis

Algae-driven photosynthetic CO2 fixation is a promising strategy to mitigate global climate changes and energy crises. Yet, the presence of metal nanoparticles (NPs), particularly dissolvable NPs, in aquatic ecosystems introduces new complexities due to their tendency to release metal ions that may perturb metabolic processes related to algal CO2 fixation. This study selected six representative metal NPs (Fe3O4, ZnO, CuO, NiO, MgO, and Ag) to investigate their impacts on CO2 fixation by algae (Chlorella vulgaris). We discovered an intriguing phenomenon that bivalent metal ions released from the metal NPs, especially from ZnO NPs, substituted Mg2+ within the porphyrin ring. This interaction led to 81.8% and 76.1% increases in Zinc-chlorophyll and Magnesium-chlorophyll contents within algal cells at 0.01 mM ZnO NPs, respectively. Integrating metabolomics and transcriptomics analyses revealed that ZnO NPs mainly promoted the photosynthesis-antenna protein pathway, porphyrin and chlorophyll metabolism, and carbon fixation pathway, thereby mitigating the adverse effects of Zn2+ substitution in light harvesting and energy transfer for CO2 fixation. Ultimately, the genes encoding Rubisco large subunit (rbcL) responsible for CO2 fixation were upregulated to 2.60-fold, resulting in a 76.3% increase in carbon fixation capacity. Similar upregulations of rbcL expression (1.13-fold) and carbon fixation capacity (76.1%) were observed in algal cells even at 0.001 mM ZnO NPs, accompanied by valuable lipid accumulation. This study offers novel insights into the molecular mechanism underlying NPs on CO2 fixation by algae and potentially introduces strategies for global carbon sequestration.

Unintended consequences of planting native and non‐native trees in treeless ecosystems to mitigate climate change

Abstract Naturally treeless ecosystems are being replaced by native and non‐native trees worldwide, often through deliberate afforestation using forestry tree species. By introducing species having novel traits, such as relatively rapid growth, many afforestation efforts also produce numerous changes in ecosystems, at the landscape scale. Trees are considered critical for climate change mitigation; indeed, many current carbon sequestration strategies rely on trees. Planting trees or allowing trees to naturally colonize through range expansions can be seen as an ideal way to increase atmospheric carbon capture. For example, a snapshot approach may show that introducing trees into treeless ecosystems enhances aboveground accumulation of carbon, helping increase ecosystem carbon storage. However, considering other impacts such as reductions in soil carbon or albedo and increased fire severity (through increases in fuel loads and connectivity) reduces the effectiveness of afforestation strategies for climate change amelioration. Additional negative impacts of afforestation are also likely, such as the reduction of native biodiversity and productivity, substantial water yield losses, and changes in nutrient cycles, which can exacerbate other global change drivers. Further, tree invasions originating from afforestation can exacerbate these negative impacts. Synthesis. This review highlights that the positive and negative impacts of planting trees in naturally treeless ecosystems as a strategy to mitigate climate change are idiosyncratic, depending on the location where trees are introduced, the time period trees are allowed to grow, and risks of spread and impacts associated with specific tree species. Although planting trees can potentially be a tool to fight climate change, a greater consideration of their impacts is required to minimize the unexpected negative consequences of afforestation efforts.

Electrochemical Gas Separations for Green Energy Integration

Separation and purification of molecules and compounds is one of the fundamental processes of chemistry and a hugely important factor in industrialization, accounting for as much as 15% of world’s energy consumption. As the world tries to limit and reduce the effects of climate change, simultaneous development of a green chemical economy and carbon sequestration strategies are needed. Both these goals need to effectively and efficiently separate gas phase molecules to make the implementation of these technologies feasible, requiring an even higher demand for economical and green gas phase separation. The current methods of gas phase separation used in industry rely predominantly on inefficient processes, such as cryogenic distillation or temperature or pressure swing absorption. Gas phase separation by electrochemical means can offer theoretically high energy efficiency separation, as the energy supplied can operate exclusively on the molecule of interest, if proper material and design criteria are met, while traditional methods act upon the entire gas mixture. Additionally, electrochemical separations can reduce the number of steps needed as they can simultaneously separate and compress the purified gas, easing the demand for high energy processing required when using mechanical pumps. However, the effectiveness of these technologies depends largely on the operating conditions and materials that make up the electrochemical cell. Thus, a key factor driving improvement in this field relies heavily on material development, such as improved membranes/separators, catalysts, and other cell materials which can in turn give rise to novel techniques and high performance of the electrochemically driven devices. Electrochemical gas phase separations integrated with green energy are critical to reaching climate change targets, but they in turn rely on the development of novel materials at enlarged scales and implementation of these technologies at reduced costs. In this article, we discuss the principles and applications of three electrochemical gas separations: hydrogen (H2) pump, ammonia (NH3)compression, and carbon dioxide (CO2) separation.

A state of the art of review on factors affecting the enhanced weathering in agricultural soil: strategies for carbon sequestration and climate mitigation.

As the urgency to address climate change intensifies, the exploration of sustainable negative emission technologies becomes imperative. Enhanced weathering (EW) represents an approach by leveraging the natural process of rock weathering to sequester atmospheric carbon dioxide (CO2) in agricultural lands. This review synthesizes current research on EW, focusing on its mechanisms, influencing factors, and pathways for successful integration into agricultural practices. It evaluates key factors such as material suitability, particle size, application rates, soil properties, and climate, which are crucial for optimizing EW's efficacy. The study highlights the multifaceted benefits of EW, including soil fertility improvement, pH regulation, and enhanced water retention, which collectively contribute to increased agricultural productivity and climate change mitigation. Furthermore, the review introduces Monitoring, Reporting, and Verification (MRV) and Carbon Dioxide Removal (CDR) verification frameworks as essential components for assessing and enhancing EW's effectiveness and credibility. By examining the current state of research and proposing avenues for future investigation, this review aims to deepen the understanding of EW's role in sustainable agriculture and climate change mitigation strategies.

Impact of spruce deadwood logs on physical properties of a loamy sand Podzol in a steep temperate forest

AbstractThinned steep forests are particularly vulnerable to soil physical degradation. Retaining deadwood logs from thinning operations on the forest floor can potentially mitigate soil physical degradation by modifying its physical properties through increased carbon content in steep regions. We aimed to investigate the effect of spruce deadwood logs from thinning operations on the physical properties of a loamy sand Podzol soil in a steep (30°) temperate spruce forest in Bavaria, Germany. The soil organic carbon (SOC) content was 56% higher under deadwood logs compared to the control areas (p‐value = 0.097). Deadwood logs also increased the soil water repellency by 13% (p‐value = 0.269), while decreasing the soil shear strength by 35% (p‐value = 0.001). Shear strength and water repellency strongly correlated with SOC content, with r = −0.87 and r = 0.86, respectively. Although retaining deadwood logs seems a promising carbon sequestration strategy, it can adversely affect soil shear strength and water repellency and potentially lead to soil degradation. Therefore, the choice to keep deadwood logs on the forest floor may align with specific management goals.

Soil Dynamics for Carbon Buildup in Different Land Use Systems in the South Region of Gujarat, India

Soil dynamics for carbon build-up vary across different land use systems. Understanding the soil dynamics and land use system management practices that contribute to carbon build-up is essential for designing effective carbon sequestration strategies. In a recent study, fifteen different land use systems were examined, including agriculture land-use systems, tree plantation land-use systems, and agroforestry land-use systems. The study assessed the potential of these land use systems to store carbon based on the extent of tree components. Various physical and chemical characteristics of the soil and their impact on soil carbon conservation were also investigated. The results showed that as the number of tree components increased, the soil pH and bulk density decreased from 6.10 to 5.55, and 1.48 to 1.33g/cm3. The available soil nitrogen was significantly higher in tree plantation land-use systems than in agriculture land use systems while soil moisture was higher in the latter. Tree components increase soil carbon build-up and agroforestry land use systems fulfill the requirement for human and environmental balance.

Trade-off of ecosystem productivity and water use related to afforestation in southcentral USA under climate change

The increase of tree canopy cover due to woody plant encroachment and tree plantations modifies both carbon and water dynamics. The tradeoffs between ecosystem net primary productivity (NPP) and water use with increasing tree cover in different climate conditions, particularly under future climate scenarios, are not well understood. Within the climate transition zone of the southern Great Plains, USA, we used the Soil and Water Assessment Tool+ (SWAT+) to investigate the combined impacts of increasing tree cover and climate change on carbon and water dynamics in three watersheds representing semiarid, subhumid, and humid climates. Model simulations incorporated two land use modifications (Baseline: existing tree cover; Forest +: increasing evergreen tree cover), in conjunction with two climate change projections (the RCP45 and the RCP85), spanning two time periods (historic: 1991–2020; future: 2070–2099). With climate change, the subhumid and humid watersheds exhibited a greater increase in evapotranspiration (ET) and a corresponding reduction in runoff compared to the semi-arid watershed, while the semi-arid and subhumid watersheds encountered pronounced losses in water availability for streams (>200 mm/year) due to increasing tree cover and climate change. With every 1 % increase in tree cover, both NPP and water use efficiency were projected to increase in all three watersheds under both climate change scenarios, with the subhumid watershed demonstrating the largest increases (>0.16 Mg/ha/year and 170 %, respectively). Increasing tree cover within grasslands, either through woody plant expansion or afforestation, boosts ecosystem NPP, particularly in subhumid regions. Nevertheless, this comes with a notable decrease in water resources, a concern made worse by future climate change. While afforestation offers the potential for greater NPP, it also brings heightened water scarcity concerns, highlighting the importance of tailoring carbon sequestration strategies within specific regions to mitigate unintended repercussions on water availability.

Evaluating CO2 hydrate kinetics in multi-layered sediments using experimental and machine learning approach: Applicable to CO2 sequestration

The transition to a low-carbon economy requires the implementation of effective carbon capture and sequestration (CCS) strategies. One of the potential CCS strategies is to capture industrial CO2 emissions and inject them into the oceanic sediments to be stored as CO2 hydrates. However, the success of this technique depends on a few key factors such as the type of sediments where CO2 is injected, the kinetics of CO2 hydrate formation and dissociation, the accuracy of the models for prediction of formation kinetics, and the CO2 hydrates morphology. So, in this first-gen work, a highly complex set of experiments was carried out to examine the CO2 hydrate formation and dissociation processes by injecting CO2 via injection tube into different size wet sediments, i.e., coarse (diameter: 0.5–1.5 mm), granules (diameter:1.5–3.0 mm) and dual-layered sand (coarse + granules), embedded inside high-pressure reactor as the artificial seabed. The experiments were carried out at 3.5 MPa at T = 1.5–2.0 °C with 500 ppm of the eco-friendly hydrate promotor (l-tryptophan). The images of morphological changes during hydrate formation/dissociation, the Scanning Electron Microscope analysis of the sediments, and the estimated water-to-hydrate conversations have been reported in this work. A novel mathematical four-parameter-based CO2 hydrate kinetics model was also developed. A set of 32,843 experimental data points was used to train a supervised machine learning algorithm using two parameters with the other two taken from published literature. The water-to-hydrate conversion was estimated and follows the order of dual-layered sand [88.26 (±4.62) %] > coarse [77.77 (±5.72) %] > granules [65.36 (±2.3) %]. The proposed ML-based model predicted the water-to-hydrate conversion with an Average Absolute Relative Deviation [%AARD] of 4.23–13.29 %. This work serves as a step forward in developing a sustainable hydrate-based oceanic carbon storage technology.

Increased drought and extreme events over continental United States under high emissions scenario

The frequency, severity, and extent of climate extremes in future will have an impact on human well-being, ecosystems, and the effectiveness of emissions mitigation and carbon sequestration strategies. The specific objectives of this study were to downscale climate data for US weather stations and analyze future trends in meteorological drought and temperature extremes over continental United States (CONUS). We used data from 4161 weather stations across the CONUS to downscale future precipitation projections from three Earth System Models (ESMs) participating in the Coupled Model Intercomparison Project Phase Six (CMIP6), specifically for the high emission scenario SSP5 8.5. Comparing historic observations with climate model projections revealed a significant bias in total annual precipitation days and total precipitation amounts. The average number of annual precipitation days across CONUS was projected to be 205 ± 26, 184 ± 33, and 181 ± 25 days in the BCC, CanESM, and UKESM models, respectively, compared to 91 ± 24 days in the observed data. Analyzing the duration of drought periods in different ecoregions of CONUS showed an increase in the number of drought months in the future (2023–2052) compared to the historical period (1989–2018). The analysis of precipitation and temperature changes in various ecoregions of CONUS revealed an increased frequency of droughts in the future, along with longer durations of warm spells. Eastern temperate forests and the Great Plains, which encompass the majority of CONUS agricultural lands, are projected to experience higher drought counts in the future. Drought projections show an increasing trend in future drought occurrences due to rising temperatures and changes in precipitation patterns. Our high-resolution climate projections can inform policy makers about the hotspots and their anticipated future trajectories.

Planting exceptional tropical tree species to increase long‐term carbon storage in assisted secondary succession

Abstract With rising atmospheric CO2 concentrations, strategies for greater carbon sequestration and long‐term storage are urgently needed. Current reforestation schemes typically use fast‐growing tree species with low wood density, limiting the amount of carbon stored. In most tropical forests, there are native species with relatively fast growth rates, high wood density and low mortality rates that also achieve large adult size—‘exceptional species’. We present a simulated assessment of the carbon sequestration potential using these exceptional species in assisted secondary succession in the Neotropics. In our example, the selected exceptional species could add up to 16.2 Mg C/ha of sequestered carbon in secondary wet forests at maturity. Synthesis and applications. By increasing the representation of exceptional species in reforestation efforts, we could potentially boost long‐term carbon storage in reforestation projects focussed on carbon sequestration. However, our approach is not a substitute for protecting existing old primary forests and reforested lands plus reducing deforestation and emissions.

The influence of biomass type on hydrothermal carbonization: Role of calcium oxalate in enhancing carbon sequestration of hydrochar

Addressing climate change through effective carbon sequestration strategies is critical. This study presents an investigation into the hydrothermal carbonization (HTC) and co-hydrothermal carbonization (Co-HTC) of invasive plants (IPs) to produce hydrochars to unveil the significant impact of biomass type and unique mineral on the stability of hydrochars. Nine hydrochars were produced from six IPs, utilizing both single and mixed biomass. A key finding is the observable that calcium oxalate forms as a surface mineral during HTC through different characterization techniques, the presence of which notably influenced the stability of hydrochars, resulting in enhanced thermal (highest R50 = 0.81) and chemical (lowest carbon loss rate = 4.02%) stability of hydrochars, possibly acting as a protective layer. Besides, a positive correlation was established between the yield of hydrochars and the lignin content of the original biomass. It is also observed that Co-HTC of plant materials rich in Ca2+ can enhance the formation of calcium oxalate minerals. This is likely due to their synergistic role in the HTC process, promoting the release of more C2O42− and Ca2+. Our results signify the crucial role of biomass composition in the HTC process and spotlight the potential of calcium oxalate in augmenting hydrochar stability. This study offers valuable insights that bolster the theoretical framework for employing hydrochar derived from IPs as a potent material for carbon sequestration.