CO2 Emissions Research Articles

Cobalt-based Molecular Electrocatalyst-Mediated Green Hydrogen Generation: A Potential Pathway for Decarbonising Steel Industry

Amid the climate change crisis, researchers are investigating the transformative potential of green hydrogen produced by renewable energy electrolysis to decarbonize the steel sector, a significant contributor to global carbon emissions. It aims to lower the carbon footprint of the steel industry by showcasing green hydrogen's potential as a cleaner substitute for traditional fossil fuels in the production process. Despite its potential, issues such as high costs, restricted availability, and infrastructural alterations must be addressed. Cobalt-based synthetic catalysts, especially cobaloximes, are being considered as a key electrocatalytic component for hydrogen production via water-splitting. Cobaloximes, noted for their efficiency and stability in catalysing hydrogen evolution, have made considerable advances in the field of molecular catalysis. Recently, advanced immobilisation procedures have appreciably enhanced their overall catalytic output and application. This article discusses several electrolyser technologies, such as proton exchange membrane (PEM) and alkaline electrolysis, highlighting the benefits of multi-stacked electrolyser systems for boosting hydrogen generation efficiency. These encouraging results are vital for unravelling a durable catalytic material that can be scaled up without much financial stringency. In light of the global climate pledges, the document concludes that green hydrogen might provide 24% of the world's energy needs by 2050, resulting in a considerable reduction in CO2 emissions.

Durability and hardened characteristics of cement mortar incorporating waste plastic and Polypropylene exposed to MgSO4 attack

Annual waste plastic disposal has grown, harming nature. Utilising this waste in concrete production may help preserve building resources. This study tested cement mortar with polyvinyl chloride (PVC) and polypropylene (PP) substituted for sand aggregate at 0, 5, 10, 15, and 20%. The samples were nevertheless exposed to a 10% and 20% MgSO4 solution for a month. The properties of both fresh and hardened materials under these circumstances have been evaluated and contrasted with those evaluated under typical circumstances. For mixes including PP and PVC, the flow diameter increased. The rounded plastic particles provided fewer contact surfaces and less friction among mixtures, which reduced water consumption and improved workability, leading to an increase in slump flow. As the amount of plastic aggregate increases, the compressive strength decreased. Moreover, this pattern might be explained by the weakening of the bond between the surfaces of the plastic aggregate and cement paste. The hydration of cement may also be hampered by the hydrophobic properties of plastic aggregate. Like compressive strength, the splitting tensile strength decreased as the replacement level of plastic ratio increased regardless of its type under all conditions (normal and exposing to MgSO4). PP and PVC fine aggregate in mortar increases sorptivity under all situations. Following screening, those circumstances and PVC have the most impact on compressive strength. increasing PVC and PP at 10% for each of them leads to lower values of compressive and tensile strength. An optimization process was implemented to determine the optimum value of PVC, PP, and MgSO4. It shows that using PVC of 3.9%, PP of 10.1%, and MgSO4 of 19.59% leads to maximum compressive and tensile strength with the minimum cost and CO2 emissions.

Calcite precipitation: The forgotten piece of lakes' carbon cycle.

Lakes emit substantial amounts of carbon dioxide (CO2) into the atmosphere, but why they do remains debated. The long-standing vision of lakes as solely respirators of the organic matter leaking from the soils has been challenged by evidence that inorganic carbon produced by weathering of the catchment bedrock could also support lake CO2 emissions. How inorganic carbon inputs ultimately generate lake CO2 outgassing remains a blind spot. We develop and introduce a calcite module in a coupled one-dimensional physical-biogeochemical model that we use to simulate the carbon cycle of the large Lake Geneva over the past 40 years. We mechanistically demonstrate how the so-far neglected process of calcite precipitation boosts net CO2 emissions at the annual scale. Far from being anecdotal, we show that calcite precipitation could explain CO2 outgassing across various lakes globally, including some of the largest lakes in the world.

The Environmental Impact of Trade Openness on CO2 Emissions: Empirical Evidence from Somalia

The Environmental Impact of Trade Openness on CO2 Emissions: Empirical Evidence from Somalia

Light-duty gasoline vehicle emission deterioration insights from large-scale inspection/maintenance data: The synergistic impact of usage characteristics

Accurately estimating vehicle emissions is crucial for effective air quality management. As key data for emission inventory construction, emission factors (EFs) are influenced by vehicle usage characteristics and experience deterioration. Current deterioration models often employ single-factor approaches based on vehicle age or accumulated mileage, which fail to capture the effects of varying usage intensities within the same mileage or age intervals. This study addressed this limitation by developing a novel emission deterioration model that incorporates multi-dimensional usage characteristics and that utilizes a large-scale inspection and maintenance (I/M) dataset for light-duty gasoline vehicles (LDGVs). The modeling results reveal distinct deterioration patterns for different pollutants and highlight the synergistic effects of the usage duration and intensity: natural aging significantly impacts HC and NOx emissions, while CO emissions are more strongly affected by intensive use. Specifically, China V LDGVs that were driven 4 × 104 km/yr exhibited HC, CO, and NOx deterioration rates per mile that were approximately 4.1 % lower, 10.3 % higher, and 1.1 % higher, respectively, than those of vehicles driven 2 × 104 km/yr as the mileage increased from 5 × 104 km to 10 × 104 km. By leveraging timely emission data and explicitly accounting for usage intensity, this study corrected biases in local emission estimates by 5–85 % with respect to estimates from commonly used models. This framework enables the development of more effective control strategies and refinements to policy evaluations in megacities with I/M programs.

Measuring carbon emission performance in China's energy market: Evidence from improved non-radial directional distance function data envelopment analysis

The most complex challenge facing the energy market is identifying effective solutions to reduce CO2 emissions (CEs) and enhance environmental performance (EP). Coal production within the power sector is the primary source of these emissions. In this study, we developed a novel linear programming model that accounts for undesirable outputs to assess the EP of 15 power enterprises in eastern China from 2016 to 2020. In addition, we employed a global non-radial Malmquist-Luenberger productivity index (GNML) to analyse the mechanisms influencing changes in efficiency among these enterprises. Our findings indicate that, while the EP of the power industry in eastern China improved, it remains at a relatively low level and exhibits instability. Moreover, technological efficiency (TE) and scale efficiency (SE) play a significant role in determining production efficiency within the sector. Therefore, it is essential for industry managers to implement standardized production management regulations, enhance technological development and scale investments, and strengthen control over unintended emissions that could facilitate energy transition.

Monitoring of Greenhouse Gas Emission Drivers in Atlantic Canadian Potato Production: A Robust Explainable Intelligent Glass-Box

In this research, a novel explainable multi-level ensemble learning framework has been developed to accurately monitor the greenhouse gas (GHG) emission drivers of the Maritime potato crop system i.e., Carbon dioxide (CO2), nitrous oxide (N2O), and water vapour (H2O). For this purpose, alongside the GHG emission drivers, the hydro-meteorological and soil properties information was collected from three Canadian sites, two in Prince Edward Island (PEI) and one in New Brunswick. This advanced framework includes a transparent multi-level pre-processing module and a Runge-Kutta optimizer (RUN), integrated with an eXplainable gradient-boosted decision Tree (GBDT) machine learning (ML) technique. The preprocessing scheme meticulously selects the most effective input combinations from the hydro-meteorological and soil properties datasets using hybridization of Boruta-GBDT for feature selection, Best Subset Least Absolute Shrinkage and Selection Operator (BSLR), and Weighted Aggregated Sum Product Assessment (WASPAS). The optimal combinations were then analyzed using the GBDT-RUN and compared against two algorithms: LightGBM coupled with RUN optimizer (LightGBM-RUN) and classical GBDT. The explainability of the primary model was enhanced using SHapley Additive exPlanations (SHAP). Model validation employed various metrics, such as the correlation coefficient (R), squared deviation (SquD), and a range of sophisticated statistical graphics. Results demonstrated that the GBDT-RUN model exhibited superior performance in monitoring GHG emissions (CO2|R=0.8431, SquD=17.1759, WASPAS=1.88E-07; N2O|R=0.8431, SquD=17.1759, WASPAS=1.88E-07; H2O| R=0.8431, SquD=17.1759, WASPAS=1.88E-07), outperforming both LightGBM-RUN and classical GBDT. Furthermore, the explainability analysis identified dew point and soil temperature as the most influential factors in the CO2, N2O, and H2O emissions scenarios.

Science and Technology of Supercapacitor and its Applications

Super-capacitors (SCs) are significant because of their unique characteristics, which include long cycle life, high strength, and environmental friendliness. SCs use electrode substances with high specific surface area and thinner dielectrics. Referring to the energy storage mechanism, all kinds of SCs were reviewed in this review paper; a quick synopsis of the materials and technology used for SCs is provided. Materials such as conducting polymers, carbon materials, metal oxides, and their composites are the main focus. The performance of the composites was evaluated using metrics such as energy, cycle performance, power capacitance, and rate capability, which also provides information on the electrolyte materials. To precisely appraise the state of Charge (SoC) in the super SCs cell module, its identical model o is used. It is expected that this model will accurately capture the features of the cell module, specifically its standing-related self-discharge behavior, and the outcomes of parameter identification directly impact its accuracy. Engine downsizing is a result of the requirement to increase fuel efficiency and lower CO2 and other hazardous pollutant emissions from internal combustion engine cars. However, smaller turbocharged engines have a relatively poor torque capability at low engine speeds. To solve this issue, an electrical torque boost based on SCs may be used to help recover energy during regenerative braking as well as during acceleration and gear changes.

Experimental investigation on diesel engine performance and emission characteristics using waste cooking oil blended with diesel as biodiesel fuel

Biodiesel production from waste cooking oil is a potential feedstock to alternative fuel sources. Produced alternative fuel sources were to have a strong emphasis on energy efficiency to substitute the declining world supply of fossil fuels while also improving emission characteristics in diesel engine applications. The development of industrialization and mechanization causes increased fossil fuel consumption and its usage. This study aimed at an experimental investigation of biodiesel blended fuel combustion efficiency for single-cylinder diesel engines under varying engine loads at constant engine speed 1500 rpm. The transesterification process was used to produce biodiesel from waste cooking oil using NaOH as catalysts. Biodiesel reaction takes place with oil to methanol ratio of 6:1 at 60 °C reaction temperature for 90 min with 600 rpm stirring speed while 90% yield gained. Eight sample biodiesel blends were prepared with percentage value B5%, B10%, B15%, B20%, B25%, B30%, B35%, B40% v/v and B100% to investigate the effect of biodiesels on engine performances. The experimental result reveals that the mixed biodiesel blends have lower average value in terms of brake torque, brake power, and brake thermal efficiency than diesel fuels as a percentage of 16.79%, 4.08%, and 27.9% respectively. In addition, the average BSFC of biodiesel blends was increased by 4.8% than baseline diesel fuel. Related to exhaust gases emission test results were shows that the average CO and HC emissions decreased by 52.2% and 60% with increasing loads and blends and the increment of CO2 and NOx by 28.1% and 45.4% respectively than baseline fuel with increasing blends and loads. Biodiesel derived from waste cooking oil was less costly and environmentally friendly and viable to substitute petro-diesel.

Integrated water resource management in the Segura Hydrographic Basin: An artificial intelligence approach

Managing resources effectively in uncertain demand, variable availability, and complex governance policies is a significant challenge. This paper presents a paradigmatic framework for addressing these issues in water management scenarios by integrating advanced physical modelling, remote sensing techniques, and Artificial Intelligence algorithms. The proposed approach accurately predicts water availability, estimates demand, and optimizes resource allocation on both short- and long-term basis, combining a comprehensive hydrological model, agronomic crop models for precise demand estimation, and Mixed-Integer Linear Programming for efficient resource distribution. In the study case of the Segura Hydrographic Basin, the approach successfully allocated approximately 642 million cubic meters (hm3) of water over six months, minimizing the deficit to 9.7% of the total estimated demand. The methodology demonstrated significant environmental benefits, reducing CO2 emissions while optimizing resource distribution. This robust solution supports informed decision-making processes, ensuring sustainable water management across diverse contexts. The generalizability of this approach allows its adaptation to other basins, contributing to improved governance and policy implementation on a broader scale. Ultimately, the methodology has been validated and integrated into the operational water management practices in the Segura Hydrographic Basin in Spain.

Technology Focus: EOR Operations (November 2024)

International agreements and national policies on environmental sustainability are changing the outlook for enhanced oil recovery (EOR) globally. These changes are highlighted by both monetary and intellectual commitments by oil companies around the world. Saudi Aramco has pledged $1.5 billion toward sustainable technology. In practice, members of Aramco’s EXPEC Advanced Research Center have collaborated with King Fahd University of Petroleum and Minerals to develop sustainable surfactants for use in high-temperature, high-pressure, and high-salinity carbonate reservoirs. They used no or only green solvents to produce soluble, stable surfactants with the potential for biodegradability. In Colombia, Ecopetrol is committed to reducing CO2 emission by 25% by 2030. As part of its efforts, it has been optimizing polymer injection in Chichimene, a heavy-oil field. By estimating life cycle greenhouse-gas emissions and energy consumption, it was able to show that polymer injection and its associated carbon intensity reduction could prevent the emission of 3,200 tons CO2 equivalent. To comply with the UK’s North Sea Transition Deal, which mandates a 50% reduction in offshore oil and gas emissions by 2030, Ithaca Energy and Energy Research Norway is using life-cycle assessment to guide more efficient heavy-oil recovery. By using low-dose polymer injection, instead of alternatives such as thermal EOR, it was able to increase exergy while also reducing CO2 emissions by 35%. In these studies, we already see the effect of the energy transition as companies turn away from traditionally effective but environmentally burdensome EOR methods such as steam injection and new polymers that show equal, if not greater, effectiveness with a reduced environmental cost. As we move forward with further regulation and innovation, it will be interesting to see how emerging technological developments in polymers, nanofluids, and even artificial intelligence can help producers meet both the economic and environmental criteria to maintain profitable fields. Recommended additional reading at OnePetro: www.onepetro.org. SPE 218653 Coinjection EOR Technology Increases Recovery and Reduces Greenhouse-Gas Emissions by G. Wasylchuk, GERI SPE 218690 Steam Generation Using Renewables Energy—An Integrated Approach for Enhanced Oil Recovery Applications by Mustafa Al Ajmi, Petroleum Development Oman, et al. SPE 218962 Reaching a Million Barrels in an Abu Dhabi Field by Focusing on Operations Efficiency by Masud J. Akhtar, Abu Dhabi National Oil Company, et al.

On the use of hydrogen in oxy-fuel glass melting furnaces: An extensive numerical study of the fuel switching effects based on coupled CFD simulations

The present study examined the potential of utilizing hydrogen as a fuel in an industrial cross-fired oxy-fuel glass melting furnace with a total energy input of 3.9 MW. To this end, comprehensive three-dimensional CFD simulations were performed in Ansys Fluent, employing a coupled numerical model from preceding works. A two-step validation process was presented, comprising the validation of both the numerical furnace setup and the modeling of industrial oxy-fuel combustion setups using hydrogen as a fuel gas. Assuming an equal thermal energy input for both combustion conditions, the fuel/oxidizer ratios of velocity and momentum of the six PrimeFire burners were found to be significantly affected. Consequently, the low-momentum flames with natural gas transformed into jet-type flames with a straighter trajectory when transitioning to hydrogen. This change led to an enhanced turbulent mixing and a reduction of flame lengths by over 25%, while the average flame temperature increased by up to 82 K due to the accelerated reaction kinetics. In addition, the elevated flame momentum in the cross-fired burner configuration resulted in a localized rise in maximum side wall temperatures by more than 20 K. With the exception of these local effects, the global temperature distribution and heat transfer mechanisms were not significantly impacted. This indicated a comparable melting process and furnace efficiency, while still allowing for a reduction of total CO2 emissions by 77.5%. Future research should concentrate on both the impact on glass quality and the evaluation of potential alternative burner configurations for hydrogen-fired oxy-fuel glass melting furnaces.

Investigating envelope retrofitting potential and resilience of Australian residential buildings − A stock modelling approach

Residential buildings consume around 24 percent of overall electricity use in Australia. Though the energy efficiency of new buildings is progressively increasing, there are around 10 million existing homes most with poor thermal and energy performance. Improving these existing homes are imperative for Australia to reach its target of net zero by 2050. This paper adopts a stock modelling approach using real designs of more than two hundred thousand detached dwellings and apartments submitted for certification in eight states and territories across Australia to investigate envelope retrofitting potential of the housing stock. The performance of the existing housing stock was assessed and the effect of various levels of envelope improvements on energy efficiency and overheating were analysed for current and future climatic conditions. With improvements in 10% of the entire building stock, 3.14 Mt, 3.52 Mt and 7.2 Mt CO2 emission reductions per year respectively were estimated with Rehab, Refurb and Renov improvements. Both detached dwellings and apartments experienced overheating across all the states and territories for the current and future climatic conditions. Though envelope improvement caused some reduction in the overheating, it was not significant. The high average overheating hours in Queensland come from nighttime overheating in the bedrooms, whereas in most other states daytime overheating constitute the majority. Various improvements in the building envelope were effective in reducing daytime overheating reductions rather than nighttime overheating, though the impact was marginal. The results from this study provided guidance on policy and regulatory mechanisms that can be introduced for developing decarbonization pathways for buildings at a national level.

Thermal-Hydraulic Characteristics of an Earth Air Heat Exchanger: An experimental analysis

The pipe layout design has a great effect on the thermal-hydraulic characteristics of earth air heat exchanger (EAHE) systems. So, in the current study proposed four new buried pipe design configurations; low to high to low, high to low to high, spiral, and circular, in addition to the straight or uniform for comparison. These five configurations are tested and analyzed experimentally depending on the thermo-hydraulic performance for summer cooling requirements with variation of Re in the range of 18041 – 40843. The results show that changing the uniform design of the EAHE with fixed pipe length enhances both the heat transfer process and pressure loss values. At the same operating conditions, the circular design has the best performance compared to the other ones. For all pipe shapes, the cooling effect increases with the increase of air Re. The thermal- hydraulic performance of the circular design pipe is higher than that of the other pipe designs. The highest coefficient of performance (COP) average values that can be obtained at Re = 18041 is 3.05 for circular shape and enhances by 48.08 % compared to uniform shape. The effectiveness of EAHE with circular shape is improved by about 3.52 % compared to uniform shape at Re = 18041. Spiral design is optimum design based on the Nu value which reaches about 48 with enhancement 12.56% and 0.34 % compared to uniform and circular shapes respectively, at Re = 40843. The hydrothermal performance factor is highest in the case of circular shape with value about 21.9 at Re = 21257. By increasing Re, the drawbacks of the increasing in the total entropy generation are reflected negatively on the exergy efficiency. The specific cost of the circular shape at Re = 40843 is the optimum value by about 0.7 $/W. Spiral and circular shapes have a decrease of CO2 emissions less than uniform shape by percentage varied from 2.93 % to 13.84% for decrease in the Re from 21257 to 40843. It is concluded that using EAHE with four new shapes is highly efficient in increasing cooling capacity and energy consumption in buildings.

Astronomical Calibration of the Ocean Anoxic Event 1b and Its Implications for the Cause of Mid‐Cretaceous Events: A Multiproxy Record

AbstractThe timing and duration of oceanic disturbances linked to Oceanic Anoxic Event (OAE) 1b, as well as the mechanisms driving anoxia and carbon burial during this period, remain subjects of debate. We conducted cyclostratigraphic analyses on magnetic susceptibility (MS) and elemental Ti and Fe series within the upper Aptian‐lower Albian interval of the Poggio le Guaine core in the Umbria‐Marche Basin, Italy. This interval provides a detailed sedimentary record, supported by variations in magnetic mineral content, Ti, Fe, and significant global shifts in the δ13C curve. Orbital control of MS, Ti, and Fe suggests a duration of 2.84 Myr for the OAE 1b event. Our chronostratigraphic analysis reveals ages of 114.07 ± 0.12 Ma for 113/Jacob, 113.28 ± 0.12 Ma for Kilian, 112.49 ± 0.12 Ma for the central age of the Monte Nerone cluster, 111.70 ± 0.12 Ma for Urbino, and 111.28 ± 0.12 Ma for Leenhardt sub‐events. Stable δ13C chemostratigraphy correlations enable the transfer of tiepoints across various sedimentary basins. Key features of the carbon isotope curves were identified, named, and dated using astrochronology. Our findings suggest that the organic‐rich layers associated with the OAE 1b event exhibit distinct characteristics influenced by several factors, including a warm climate driven by volcanic CO2 emissions, heightened precipitation, intense weathering, and marine transgressions. These factors amplify orbital forcings on paleoclimate changes, leading to oceanic‐atmospheric disturbances that promote deoxygenation and carbon burial during OAE 1b.

Solar-driven collaborative thermochemical energy storage and fuel production via integrating calcium looping and redox cycle

To better utilize solar energy and reduce CO2 emissions, this study proposes a novel idea of solar-driven thermochemical energy storage and fuel production via integrating calcium looping and redox cycle. Such integrated system design not only can realize solar energy storage and CO2 capture based on thermochemical reversible reaction of CaO/CaCO3, but also can achieve fuel production through thermochemical conversion of captured CO2 into CO based on redox cycle. More interestingly, the temperature required for CaCO3 calcination of calcium looping matches the temperature for the oxidation reaction of redox cycle, which means a good connection between calcium looping and redox cycle. Additionally, a solar-driven thermochemical reactor system and its comprehensive thermodynamic model of calcium looping and redox cycle are developed to present the performance of integrated system. Results indicate that such integrated system can achieve a 43.54 % of solar energy converted into chemical energy (40.53 % obtained by calcium looping and 3.01 % obtained by redox cycle) even after 100 cycles. Moreover, the solar-to-chemical efficiency can reach 57.69 % and solar-to-fuel efficiency can reach 32.76 % after 100 cycles, when the heat recovery is considered (heat recovery effectiveness is assumed to be ηrecovery = 70 % in this work). This study presents a promising path to simultaneously achieve solar energy storage, CO2 capture and renewable fuel production.

High-temperature performance of clay-enhanced alkali-activated binders: A sustainable alternative to Portland cement

The cement industry's commitment to reducing CO2 emissions has led to exploring alternative processes and supplementary cementitious materials (SCMs). These include alkali-activated binders or geopolymers, promising cement alternatives due to their pozzolanic properties and superior strength and durability, especially at high temperatures. Using abundant raw materials such as clay further enhances the sustainability of geopolymers by reducing emissions associated with their production. Factors like raw material composition and activator type can affect binder properties, so careful material design is essential. This paper discusses experimental results on the mechanical behaviour of alkaline cements at high temperatures, testing two binders (FA=100 % fly ash and FB=70 % fly ash with 30 % clay) and two activators (WN and WK), selected from previous studies where residual strength after temperature exposure was excellent. Their performance was compared to two Portland types of cement (CEM I 52.5 N/SR and CEM I 42.5 R). Unlike cement pastes, the alkaline cements FA and FB retain and can even improve mechanical strength up to 600 °C. At this temperature, adding clay to the FB alkali cement promotes the formation of a viscous gel capable of filling cracks and voids in the geopolymer, thus increasing its high-temperature strength by 80 % compared to cement pastes.

The effects of climate change technology spillovers on carbon emissions across European countries

To unravel the challenges in the global diffusion of climate-friendly technologies, this investigation analyzes the diffusion of climate change-related technologies across countries. By using an unbalanced panel of selected European countries over the period 1990-2020, this investigation quantifies the carbon dioxide (CO2) emission effects of the diffusion of climate change-related technologies that are mediated by imports, geographical and technological proximity and free diffusion of technologies. In this study, the effects of domestic development of climate change-related technologies, population and affluence are also accounted for, and the emission effects are estimated using a fixed-effects panel model with instrumental variables. The instrumental variable for foreign technology spillovers is based on the technology support policies adopted in foreign countries. As expected, international spillovers of climate-friendly technologies are negatively linked to CO2 emissions, thus promoting emission reductions across the region. Importantly, emission reductions in Europe are more strongly influenced by international technology spillovers than by domestic innovation activities. Moreover, while all the analyzed technology diffusion channels appear relevant, the results are the most robust regarding import-mediated technology spillovers. Insights from this study support policy recommendations, especially in the trade policy context.

The performance analysis of a compressed air energy storage (CAES) for peak moving with cooling, Heating, and power production

This study focuses on modeling and optimizing a multifaceted geothermal-based energy production system within the context of Denmark. The primary objectives revolve around enhancing system efficiency and reducing operational costs. The system under investigation comprises geothermal components, an organic Rankine cycle, a compressed air energy storage facility, and an absorption chiller. The organic Rankine cycle operates using refrigerants R123 and ammonia, effectively converting thermal energy into electricity and thermal energy for various applications. Optimization was carried out employing the Response Surface Method in tandem with Design-Expert software, facilitating the fine-tuning of objective functions. Two key objectives were selected: Exergy Round Trip Efficiency and cost rate, aimed at improving technical performance and curbing economic expenditure. A range of design variables were considered for optimization, including turbine and pump inlet temperatures, geothermal mass flow rate, turbine and pump efficiencies, compressor and gas turbine efficiency, inlet pressure to the compressed air energy storage tank, and evaporator pinch point temperature. The system reached an impressive exergy efficiency peak of 77.98%, accompanied by a modest cost rate of 5.48 $/h. The costliest components in the system were the compressed air energy storage unit, followed closely by organic Rankine cycle 1 and organic Rankine cycle 2. In contemplating the practical implementation of this innovative energy system, ten cities in Denmark underwent rigorous analysis, accounting for technical and economic factors. Subsequent assessments identified Aarhus as the optimal location to initiate the system. The environmental results showed that by producing 13981.9 megawatts of electricity annually in Arhus City, it is possible to help reduce CO2 emissions by 2853.2 tons of CO2/year and avoid environmental costs of 68455.3 $/year. The environmental assessment also highlighted the potential for substantial green space expansion, estimating an additional 13 hectares of green areas in the city of Aarhus, Denmark.

Synergizing carbon sequestration mechanisms during the remediation of Cr(VI) by nano zero-valent iron loaded biochar (nZVI-BC)

Applying nano zero-valent iron loaded biochar (nZVI-BC) to remediate soil heavy metal pollution has been frequently tested in current studies. However, little knowledge has been disclosed regarding the effect of nZVI-BC on soil organic carbon (SOC) mineralization/sequestration. In this study, the dual effect of nZVI-BC addition on Cr(VI) removal and SOC mineralization/sequestration and the underlying mechanisms were explored, based on a 90 days laboratory soil incubation. The results confirmed that nZVI-BC significantly improved the Cr(VI) removal rate while markedly reducing the cumulative CO2 emissions. Following the 90 days incubation, nZVI-BC addition notably increased the contents of Fe-oxides, Fe-bound organic carbon (Fe-OC), and SOC. Pearson correlation and PLS-SEM analyses indicated that the enhanced Fe-OC content, resulting from increased Fe-oxides, was a critical abiotic mechanism for improved SOC preservation. Additionally, the observed decrease in enzymatic activity and the shift in bacterial community from unstable carbon-dominant taxa (e.g., Proteobacteria and Actinobacteria) to stable carbon-dominant taxa (e.g., Firmicutes) in the nZVI-BC treatments suggested that SOC bio-mineralization was also inhibited. Overall, this study demonstrates that nZVI-BC not only aids in heavy metal remediation but also promotes long-term SOC preservation.