Efficient Carbon Research Articles

Synthesis of Ag/NiFe2O4 doped multiwalled carbon nanotube for antibiotic removal from water

Antibiotics impose severe impacts on humans and the ambient water environment by creating antimicrobial resistance in bacterial pathogens; therefore, there exists an urgent need to develop sustainable and efficient adsorbents for the removal of these contaminants from the water. To this goal, silver/nickel ferrite-doped multiwalled carbon nanotubes (Ag/NiFe2O4 doped MWCNTs) were prepared as functional integrated adsorbent material for antibiotic removal from water. The TEM results showed that Ag/NiFe2O4 species were dispersed on the surface of MWCNTs through the available functional groups on their surface. The introduction of Ag/NiFe2O4 nanocomposite onto the MWCNTs efficiently improved the adsorption capacity for ciprofloxacin. The maximum adsorption capacity is estimated to be 26.45 mg/g. The results indicated a higher adsorptive capacity for the produced ternary sample compared to pristine MWCNTs, Ag/NiFe2O4, or NiFe2O4/MWCNTs binary systems. The adsorption capacity for ciprofloxacin in the samples was evidently dependent on the MWCNTs dose, solution pH, adsorbate dose, and temperature. Ag/NiFe2O4 doped MWCNTs (65 % w/w) were able to remove ∼95 % of ciprofloxacin in the testing solution even after being reclaimed for 4 times following the Langmuir isotherm model in the endothermic manner. Also, the adsorption of CIP by the nanocomposite demonstrates a pseudo-second-order model. These promising results open a pathway for efficient carbon materials to be replaced by conventional adsorbents to remove antibiotics from water.

Comprehensive evaluation and application of woody plants in the green spaces of parks in saline-Alkaline areas from a low-carbon perspective: A case study of Tianjin Qiaoyuan Park.

The field of landscape architecture has placed significant emphasis on low-carbon landscapes due to the increasing challenges posed by global warming and environmental deterioration in recent years. The soil ecological conditions in saline-alkaline areas are characterized by poor quality, resulting in suboptimal growth conditions for trees. This, in turn, hampers their ability to effectively sequester carbon, thereby diminishing the potential benefits of carbon sinks. Additionally, the maintenance of tree landscapes in such areas generates more carbon emissions than does conventional green land, making it difficult to reap the benefits of tree-based carbon. A comprehensive evaluation of trees in green park spaces in saline-alkaline areas is conducted from a low-carbon perspective; by identifying the dominant tree species that are well suited to greening, we can offer a precise scientific foundation for implementing low-carbon greening initiatives in cities situated in saline-alkaline environments. Therefore, as a case study, this study investigates Tianjin Qiaoyuan Park, a typical saline park in the Bohai Bay region. The hierarchical analysis method (AHP) was used to evaluate 50 species of trees and shrubs in the park from a low-carbon perspective. The results show that the evaluation system consists of four criterion layers and 15 indicator factors. The relative weight of the criterion layer followed the order of habitat adaptability (B2) > carbon sequestration capacity (B1) > low-carbon management and conservation (B3) > landscape aesthetics (B4). The indicator layer assigned greater weight values to net assimilation (C1), saline and alkaline adaptability (C3), drought tolerance (C4), irr igation and fertilization needs (C8), growth rate (C2), and adaptability to barrenness (C5). The trees were classified into five distinct categories, with each exhibiting significant variation in terms of the strengths and weaknesses of the indicators. According to the comprehensive score, the trees were categorized into three levels. The Grade I plants exhibited the best carbon efficiency performance, comprising a total of 12 species (e.g. Sabina chinensis, Fraxinus chinensis 'Aurea' and Hibiscus syriacu), and demonstrated superior performance in all aspects. Grade II trees, consisting of 26 species (e.g Pinus tabuliformis, Paulownia fortunei, Ligustrum × vicaryi), had the second-highest comprehensive score. Moreover, Grade III trees, encompassing 12 species (e.g Acer mono, Cedrus deodara, Magnolia denudata), exhibited lower comprehensive scores. The extensive use of Grade I and II tree species is recommended in the implementation of low-carbon greening projects in the Bohai Bay region, while Grade III tree species should be judiciously utilized. The findings of this research can serve as a valuable resource for the scientific identification of tree species that are suitable for urban park green spaces in the Bohai Bay region, which is characterized by predominantly saline and alkaline soil. Additionally, the development of an evaluation system can guide the selection of low-carbon tree species when evaluating other types of saline and alkaline lands.

Myo-inositol as a carbon source in Chlorella sp. production

The study aimed to investigate the possible use of myo-inositol as a carbon source in Chlorella sp. culture. Firstly, experiments were conducted with different myo-inositol concentrations and glycerol in flasks. Secondly, a laboratory-scale tubular photobioreactor (PBR) was operated with CO2 and myo-inositol to determine performance under industrial production conditions. The highest dry weight of the experiments with flasks was 1.62 ± 0.02 g.L−1 and was obtained with 1 g.L−1 myo-inositol concentration. Myo-inositol yielded two times higher lipid accumulation compared to glycerol in the experiment with flasks and 12 % compared to CO2 in the PBR experiment. The results revealed that myo-inositol is one of the most efficient carbon sources with 0.86 CBCR (carbon to biomass conversion rate). Even if myo-inositol is more expensive than many carbon sources such as CO2, high efficiency and less light energy expenses make it a competitive carbon source in Chlorella sp. production.

Carbon nanofiber/taurine-catalyzed synthesis of coumarin and 1,2,4,5-tetra-substituted imidazole derivatives under metal-free conditions

The main subject of this research is the development of a suitable, efficient, and biocompatible carbon nanofiber-based catalytic system for the synthesis of coumarin and 1,2,4,5-tetra-substituted imidazoles. Brønsted acid carbon nanofiber/taurine catalyst was made during three steps: acid treatment, acylation, and then amination. The basic principles and general advantages of the synthesis method are elaborated. The acidity of the prepared nano-catalyst was investigated using the Hammet acidity technique and UV–Vis spectroscopy, and the H0 value for 5 × 10–2 mg/mL of CNF/T in 0.3 mM 4-nitroaniline solution was determined to be 1.47. The structure of the catalyst was successfully characterized using FT-IR, TGA, FESEM, XRD, TEM, EDX, EDS-MAP, BET, and XPS techniques. Here, we report the ability of carbon nanofiber/taurine as a Brønsted acid catalyst for the synthesis of coumarins and 1,2,4,5-tetra-substituted imidazole through a metal-free, cost-effective, and biocompatible multicomponent route. Among the advantages of this protocol are reaction time, excellent efficiency, reusability, and high activity of the catalyst.

Strategic Integration: Fostering Sustainability in Low-Income Country through Poverty Alleviation, Carbon Efficiency, Energy and Economic Resilience

This study emphasizes the critical importance of strategic integration for sustainable development goals (specifically Goals 1 and 2) in low-income countries (LICs). The research uses econometric models to focus on poverty reduction, economic resilience, energy use, and carbon emissions in Indonesia from 1996 to 2022. The study reveals a long-run co-integration among the estimated parameters, with a significant speed of adjustment at a 1.04% level. ECM models highlight a positive relationship between energy use, poverty, and carbon emissions while indicating a negative association between economic growth and carbon emissions. Robustness checks support these findings, including Fully Modified Ordinary Least Squares (FMOLS) and Canonical Co-Integrating Regression (CCR). Granger causality analysis reveals a unidirectional causality from energy use to carbon emissions and economic growth, along with one-way causation from carbon emissions to economic growth and poverty. Diagnostic tests affirm the model's reliability. The study's outcomes contribute valuable insights to the discourse on strategic integration, offering policymakers and stakeholders guidance in formulating sustainable development strategies tailored to the unique challenges encountered by low-income countries.

Boosting carbon utilization efficiency for sustainable methanol production from biomass: Techno-economic and environmental analysis

Concerns about depleted fossil fuels and the climate crisis have intensified the interest in producing biomass-derived methanol. However, the traditional biomass-to-methanol (BTM) process suffers from low carbon conversion ability and serious CO2 emissions caused by the water–gas-shift (WGS) unit. In this study, three novel BTM processes coupled with solid oxide electrolysis, methane pyrolysis, and methane chemical looping technologies are proposed to eliminate WGS unit, and the systematic heat integration is considered to achieve energy cascade utilization. Meanwhile, process performances are comprehensively evaluated to compare the technical, economic, and environmental attractiveness of three novel BTM processes. It is found that compared with the original BTM process, three novel processes significantly improve carbon efficiency by 22%. Meanwhile, CO2 emissions are reduced by 60%. Moreover, the application of methane chemical looping technology is more economical, and the associated net production cost decreases by more than 30%. Additionally, the BTM process coupled with solid oxide electrolysis is more environmentally friendly, whereas the process with methane pyrolysis technology is more exergy-efficient. Overall, the integrated processes have significant application prospects for carbon conversion and mitigation ability as well as economic attractiveness.

Can green fiscal policy improve green total factor carbon efficiency? Evidence from China

Green fiscal policy has emerged as a crucial tool for promoting sustainable development in developing countries. The “National Comprehensive Demonstration City of Energy Conservation and Emission Reduction Fiscal Policy” (ECER fiscal policy) launched by the Chinese government in 2011 is a typical green fiscal policy, but its effect remains to be evaluated. This study measures the green total factor carbon efficiency (GTFCE) of Chinese cities from 2004 to 2019 and employs a time-varying difference-in-differences (DID) model to assess the causal effect of the ECER fiscal policy on GTFCE. The findings suggest that the ECER fiscal policy, combining financial incentives and environmental regulation attributes, can effectively enhance GTFCE in pilot cities. Mechanism analysis demonstrates that the low-carbon effect of the ECER fiscal policy is mainly through optimizing resource allocation and facilitating green innovation. Heterogeneity analysis further highlights the policy’s amplified impact in cities with officials under 54 years old and higher environmental attention from local governments. These findings offer valuable insights for policymakers in developing countries regarding fiscal policy optimization in advancing carbon reduction.

Comprehensive Evaluation of Decarbonization Technologies: A Case Study of Residential Buildings in Zhuzhou City, China

Efficient carbon emission reduction technologies in buildings are necessary for achieving the “Dual carbon” goal in China. In this study, a comprehensive evaluation model is proposed to assess the effect of carbon emission reduction based on the analytic hierarchy process–entropy weight–coefficient of variation model which takes newly built residential buildings in Zhuzhou City as the research object. The results show that the preferred materials for the roof and exterior walls of the building’s envelope structure were flame-retardant extruded polystyrene boards, and porous shale bricks were preferred as the main materials for the exterior walls. In addition, the rooftop solar photovoltaic system and energy-saving air conditioning technology were suitable in terms of being renewable and were better utilized. In the end, carbon emissions were significantly reduced when using the building decarbonization technologies. This study provides a new reference for choosing materials and technologies for the design of residential buildings in Hunan Province and even other regions with hot summers and cold winters.

Optimized submerged batch fermentation for metabolic switching in Streptomyces yanglinensis 3-10 providing platform for reveromycin A and B biosynthesis, engineering, and production.

The cultivation system requires that the approach providing biomass for all types of metabolic analysis is of excellent quality and reliability. This study was conducted to enhance the efficiency and yield of antifungal substance (AFS) production in Streptomyces yanglinensis 3-10 by optimizing operation conditions of aeration, agitation, carbon source, and incubation time in a fermenter. Dissolved oxygen (DO) and pH were found to play significant roles in AFS production. The optimum pH for the production of AFS in S. yanglinensis 3-10 was found to be 6.5. As the AFS synthesis is generally thought to be an aerobic process, DO plays a significant role. The synthesis of bioactive compounds can vary depending on how DO affects growth rate. This study validates that the high growth rate and antifungal activity required a minimum DO concentration of approximately 20% saturation. The DO supply in a fermenter can be raised once agitation and aeration have been adjusted. Consequently, DO can stimulate the development of bacteria and enzyme production. A large shearing effect could result from the extreme agitation, harming the cell and deactivating its products. The highest inhibition zone diameter (IZD) was obtained with 3% starch, making starch a more efficient carbon source than glucose. Temperature is another important factor affecting AFS production. The needed fermentation time would increase and AFS production would be reduced by the too-low operating temperature. Furthermore, large-scale fermenters are challenging to manage at temperatures that are far below from room temperature. According to this research, 28°C is the ideal temperature for the fermentation of S. yanglinensis 3-10. The current study deals with the optimization of submerged batch fermentation involving the modification of operation conditions to effectively enhance the efficiency and yield of AFS production in S. yanglinensis 3-10.

Pyrolysis fuel oil-derived hollow carbon nanocages as high-stability anode materials for potassium ion storage

The use of graphite to make anode materials for potassium-ion batteries (KIBs) results in diminished electrochemical performance, largely due to significant interlayer expansion caused by potassation/depotassiation. To address this limitation, novel hollow carbon nanocages (HCNCs) are prepared from pyrolysis fuel oil (PFO), a cost-effective byproduct. The HCNCs heat-treated at 1500 °C has a graphitic structure with high porosities and numerous closed pores and exhibits a notable potassium-ion storage capacity of 307.2 mAh/g at a current density of 50 mA g−1. Moreover, structurally stable HCNCs withstand the substantial volume expansion associated with potassium-ion intercalation. The stability of the material is attributed to a hybrid adsorption/insertion mechanism, which results from synergistic interplay between the unique morphologies of the HCNCs and the developed carbon layers. This configuration delivers a specific capacity of 131.6 mAh/g and 98.9 % capacity retention over 1000 cycles at a high current density of 2000 mA g−1. Consequently, these proposed HCNCs present a significant advance in developing efficient carbon materials for KIBs, and addressing the critical challenges of graphite such as unstable cycling stability.

Estimating the energy return on investment of forestry biomass: Impacts of feedstock, production techniques and post‐processing

AbstractThe Energy Return On Investment (EROI) is a recognised indicator for assessing the relevance of an energy project in terms of net energy delivered to society. For woody biomass divergences remain on the right methodology to assess the EROI leading to large variations in the published estimates. This article presents an in‐depth discussion about the EROI of woody biomass in three different forms: woodchips, pellets and liquid fuels. The conceptualisation of EROI is further developed to reach a consistent definition for biomass post‐processed fuels. It considers, on top of the external energy investments, the grey energy associated with the energy used to enrich the fuel. With the proposed methodology, all woodchips have an EROI of the same order of magnitude, between 20 and 37, depending on forestry types, operations and machineries. For secondary residues, the first estimate is 170 if, as co‐products, no energy investment is allocated to the forestry operations and transport. On the basis of a mass allocation for forestry operations and transport, the EROI for secondary residues becomes of the same order of magnitude as that for wood chips. Woodchips can be further post‐processed into pellets or liquid fuels. Pellets have an EROI of 4–7 if the heat is externally supplied and 8–23 if internally supplied (self‐consumption of part of the raw material). Liquid fuels derived from primary wood and residues through gasification and Fischer‐Tropsch synthesis have an EROI between 4 and 16. Fuel enhancement with hydrogen (Power & Biomass to Liquids) impacts negatively the EROI due to the low EROI of hydrogen produced from renewable electricity. However, these fuels offer other advantages such as improved carbon efficiency. A correct estimate of EROI for forestry biomass, as proposed in this work, is a necessary dimension in assessing the suitability of a project.

Direct carbonation of porous materials produced from self-hardened paper mill fly ash

A high-Ca fly ash generated from a paper mill using a fluidized bed boiler was used as the potential medium to sequester CO2 via the direct carbonation process. In this study, the fly ash samples were exposed to accelerated carbonation to produce hardened pastes. The influence of the porosity controlled by the amount of foam in the matrix for maximizing CO2 sequestration was determined. The effect of porosity on carbonation was evident. The samples prepared with 40 % foam and a water-to-fly ash ratio of 0.79 recorded porosities of 56.1 % (carbonated) and 66.8 % (naturally carbonated (NC)) with the lowest mechanical strength of 2.1 and 1.1 MPa, respectively. These naturally carbonated (NC) samples have been cured naturally without using high CO2 pressure. Meanwhile, the samples prepared with 10 % foam and a water-to-fly ash ratio of 0.5 recorded porosities of 41.1 % (carbonated) and 52.9 % (NC) with the highest strength at 10.2 and 4.6 MPa, respectively. The highest carbonation efficiency determined by thermogravimetric analysis was obtained from the carbonated samples with 40 % foam. Scanning electron microscopy–energy-dispersive spectroscopy depicted the areas with high Al/Si content but low Ca–O content (dark areas) and carbonated areas with high Ca–O content (bright areas). Mercury intrusion porosimetry was used to determine the pore size distribution, whereby the samples were dominated by large capillary pores, resulting in their high porosity in this study.

The Current Status and Future Prospects of Carbon Capture, Carbon Transportation, And Carbon Utilization Technologies in Chinese Coal-Fired Power Plants Within the Context of Dual Carbon Goals

Carbon dioxide capture, utilization, and storage (CCUS) constitute vital measures for achieving net emissions reduction in China. Against the backdrop of the “dual carbon” initiative in China, this paper meticulously examines and analyzes the key technological principles, merits and demerits, and bottlenecks associated with CCUS carbon capture in the country’s thermal power plants at the current stage. It combines the prevailing industrial application status and the future development trajectory of pertinent technologies with considerations of industrial economic benefits and business models. Building upon this analysis, the paper summarizes the application status of CCUS technology in China’s thermal power plant industry and presents future prospects. On the technological front, the three capture methods grapple with the challenge of high costs. Therefore, there is a need to intensify efforts in developing low-cost and efficient carbon capture materials, as well as researching and practically applying low-cost oxygen generation technology. Economically, CCUS technology currently faces high costs, low returns, and certain commercial barriers, placing China in a demonstrative business model stage. To overcome these challenges and realize the economic benefits of CCUS technology, government incentives and technological innovation are imperative. These measures aim to reduce the overall cost of CCUS technology, stimulate the scale development, and foster commercialization, ultimately contributing to the achievement of China’s carbon emission reduction targets.

Facile one-pot green synthesis of Aloe vera mediated silver nanoparticles and their catalytic efficiency towards organic transformations

A facile approach for the synthesis of Aloe vera mediated silver nano-particles (AgNPs) has been carried out via chemical route. The developed Aloe vera mediated AgNPs were characterized by using various techniques such as SEM, FT-IR etc. Additionally, catalytic applications of this interesting nanomaterial were utilized for the synthesis of 4-phenylthiazole- 2-amine and its derivatives. After completion of catalytic reactions, Aloe vera mediated AgNPs were easily recycled without any significant loss in catalytic activity. The robust features of the current approach involve an outstanding catalytic performance, ease of catalyst retrievability, easy work up procedure, and large substrate tolerance. Besides this, the green chemistry metrics for the products formed such as E-factor (Environment Factor), PMI (Process Mass Intensity), RME (Reaction Mass Efficiency), Atom Economy (AE) and carbon efficiency (CE) were in associated with high efficiency and selectivity which further confirms the effectiveness of this approach. This work highlights the significance of using economic and eco-friendly approach for synthesizing thiazole derivatives in good to excellent yields via Aloe vera mediated AgNPs under waste free conditions.

Cooperative management can mitigate trade-offs between livestock production and ecological functions to promote grassland sustainability

An increase in the population in pastoral regions and an improvement in living standards have increased livestock production; however, this has led, at least in part, to global grassland degradation. Consequently, the optimal pathway to mitigate trade-offs between livestock production and ecological functions of grassland is the key to achieve sustainable development in pastoral regions. Transformative adaptation is the recommended and feasible approach. However, most studies are not designed to determine which grassland management system addresses transformative adaptation and, therefore, do not provide options that can resolve the trade-offs. To fill this gap, we compared three grassland management systems, namely single, joint and cooperative. The grassland health index (GHI), data envelopment analysis (DEA), life cycle assessment (LCA), TOPSIS model and the multi-objective optimization model were employed to assess the productive and ecological benefits of the three systems. Cooperative management had the greatest comprehensive benefits when considering ecological functions, livestock production, carbon efficiency utilization and grassland area utilization efficiency, and had the greatest potential to achieve a balance between livestock production and ecological functions in the future.

Investigating the influence of oxygen doping in modulating product distribution for electrocatalytic CO2 reduction reaction

Efficient carbon recycling hinges on a comprehensive understanding of the mechanics behind electrocatalytic carbon dioxide reduction reactions (ECO2RR). Here, we have engineered, in-situ growth of CuO featured on O-doped gCN (COG) and ex-situ growth of CuO on bare gCN (CG) respectively, functioned as platforms fordisengaging the fundamental of ECO2RR. The COG holds substantial capacity compared to CG for efficient conversion of CO2 into hydrocarbons and initiated the C2 product pathway with enlarged faradaic efficiency (FE). The experimental results indicate that the COG enhanced the product conversion of CH3OH (FE = 61.5% ± 0.5), C2H5OH (FE = 24.7% ± 0.5), and HCOO– (FE = 6.1% ± 0.5) at −1.1 V Vs RHE. Meanwhile, the CG exhibited the maximum conversion of CO2 into CH3OH (FE = 56.4% ± 0.5) at the same potential range. For the CG, the partial current density of CH3OH (JCH3OH) is −1.8 mA cm−2, whereas COG exhibited −4.9 mA cm−2. Interestingly, in this ECO2RR, the study of oxygen doping demonstrated that feasible CO2 conversion, due to its affinity towards CO2 and high donor density.

Facile Preparation of Stable NiII‐ and CoII‐tetraaminophthalocyanine Electropolymers for Highly Efficient Heterogeneous Carbon Dioxide Reduction

This study focused on preparation of stable polymer films of NiII‐ and CoII‐tetraaminophthalocyanines, p‐NiTAPc and p‐CoTAPc, respectively, for highly efficient heterogeneous electrochemical carbon dioxide (CO2) reduction in a flow electrolysis cell. Major development represented in this work was fabrication of p‐NiTAPc and p‐CoTAPc films via electropolymerization of their corresponding monomers on carbon‐based substrates without using binder or conducting additive materials to obtain efficient gas diffusion electrodes (GDEs) for scalable, productive and selective CO2‐to‐CO conversion. The target polymers were characterized by UV‐visible spectrophotometry, attenuated total reflection‐Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X‐ray spectroscopy and cyclic voltammetry. According to controlled potential electrolysis and gas chromatography, p‐NiTAPc‐catalyzed CO2 reduction at –0.99V vs. reversible hydrogen electrode (RHE) gave 953 mL of CO in a period of 16 hours with current density and Faradaic efficiency (FE) of 109±1 mA·cm‐2 and 99±2%, respectively. A p‐CoTAPc‐modified GDE exhibited superior catalytic performance to the case of p‐NiTAPc in terms of catalyst stability and CO productivity by performing the continuous CO2 reduction at the potential of –1.10 V vs. RHE for up to 41 hours and affording almost 3 times higher amount of CO with the current density of 161±5 mA/cm2 and 95±2% FE.

Sulfonated Chitosan Gel Membrane with Confined Amine Carriers for Stable and Efficient Carbon Dioxide Capture.

Capturing carbon dioxide (CO2) from flue gases is a crucial step towards reducing CO2 emissions. Among the various carbon capture methods, facilitated transport membranes (FTMs) have emerged as a promising technology for CO2 capture owing to their high efficiency and low energy consumption in separating CO2. However, FTMs still face the challenge of losing mobile carriers due to weak interaction between the carriers and membrane matrix. Herein, we report a sulfonated chitosan (SCS) gel membrane with confined amine carriers for effective CO2 capture. In this structure, diethylenetriamine (DETA) as a CO2-mobile carrier is confined within the SCS gel membrane via electrostatic forces, which can react reversibly with CO2 and thus greatly facilitate its transport. The SCS ion gel membrane allows for the fast diffusion of amine carriers within it while blocking the diffusion of nonreactive gases, like N2. Thus, the prepared membrane exhibits exceptional CO2 separation capabilities when tested under simulated flue gas conditions with CO2 permeance of 1155 GPU and an ultra-high CO2/N2 selectivity of above 550. Moreover, the membrane retains a stable separation performance during the 170 h continuous test. The excellent CO2 separation performance demonstrates the high potential of gel membranes for CO2 capture from flue gas.

Structure and composition of rehabilitated mangrove in Lubuk Kertang Village, North Sumatra, Indonesia

Mangroves are generally distributed in tidal zones along tropical and subtropical coasts and are known as woody halophytes. Mangroves are one of the most productive and efficient long-term natural carbon sinks. Deforestation and mangrove degradation produced substantial carbon emissions that account for the majority and salt marshes emissions. Mangroves play an important role in protecting against storms and sea level rise, preventing coastline erosion, regulating coastal water quality, providing habitat for commercial interests. This study was conducted to measure the diversity, structure and composition of forests in the rehabilitation of abandoned pond mangrove forests in Lubuk Kertang Village, West Brandan District, Langkat Regency, North Sumatra. The method used was to conduct a census in a 1.6 ha restoration forest by measuring the overall diameter, height and species found. Fourteen species were found, namely Aegiceras corniculatum, Avicennia marina, Acrostichum aureum, Bruguiera gymnorrhiza, Ceriops tags, Exoecaria agallocha, Finlaysonia maritimea, Nypa fruticans Rhizophora apiculata, Rhizophora mucronata, Rhizophora stylosa, Sonneratia alba, Scyphiphora hydrophyllacea, Sesuvium portulacastrum.

Study on geothermal energy self-recycling extraction and ScCO2 storage in the horizontal well annuli with fracture network system

With the extensive exploitation of fossil fuels, a substantial number of production and injection wells have been or are on the verge of being abandoned. However, many of these wells present viable opportunities for geothermal energy extraction, as they are situated in geothermal reservoirs with favourable temperatures. In alignment with carbon neutrality policies, supercritical CO2 (ScCO2) has emerged as the preferred working fluid for geothermal extraction, facilitating subsequent storage. This study has developed three transient models to characterize the heat and mass transfer processes of ScCO2 circulating within a horizontal wellbore and the reservoir's fracture network. Finite element method and Comsol Multiphysics 6.1 software are employed to solve these models. Results show that ScCO2 efficiently flows from the annuli into the hydraulic fracture network and then circulates back through the annuli completing a self-recycling heat extraction process. The findings reveal several key insights: (a) Lower injection mass flow rates and flow rates lead to more efficient extraction of thermal energy within horizontal wellbores. (b) Low-temperature ScCO2 enhance thermal energy recovery. (c) The larger the coverage area of the fracture network, the more effective the heat extraction. (d) The efficiency of heat extraction and ScCO2 storage in the horizontal well-fracture network self-circulation system is 3 to 5 times and 6 to 7 times higher than that of the horizontal well self-recycling and injection-production systems. (e) Periodic thermal extraction proves to be more efficient than continuous methods. (f) The cumulative heat production of the vertical dual well injection-production system is the highest, reaching 2.45 × 1011 kJ. But it's still lower than the self-circulating system. The heat extraction effect of the diagonal dual well injection-production system is the lowest, which is 1.83 × 1011 kJ. (g) Three developed transient models facilitate efficient heat extraction and ScCO2 storage reservoir screening and evaluation. In conclusion, the self-recycling system has achieved efficient heat extraction and carbon dioxide storage, providing a theoretical basis for future energy conversion and management.