Search Results (2,287)

Urban agglomerations concentrate activities that generate both PM2.5 pollution and carbon emissions, but the economic basis for governing them jointly remains unclear. Taking the Yangtze River Delta as a case, this study evaluates pollution–carbon co-governance from a marginal abatement cost (MAC) perspective. Using panel data for 41 cities from 2011 to 2023, we estimate shadow prices and MACs under joint and single-objective abatement scenarios with a non-radial directional distance function dual model. We then construct carbon-reduction and pollution-reduction cost-saving effects, classify synergy types, and examine their temporal, spatial, and nonlinear transition patterns. The results show that joint abatement generally lowers the MACs of both carbon mitigation and PM2.5 reduction, with stronger cost-saving on the pollution side. Under the baseline classification, the share of balanced synergy increases over time, and the balanced state shows high persistence in Markov transitions. Core cities show weaker measured cost-saving effects, which may reflect limited remaining low-cost co-abatement potential rather than weak governance. Semiparametric evidence further indicates that industrial upgrading, openness, and urbanization are nonlinearly associated with MACs and synergy balance. These findings suggest that urban pollution–carbon coordination should be guided by local cost structures and development stages. Full article

Hydrogen Fuel Cell Electric Buses (FCEBs) are a promising solution for decarbonizing public transport. Their operational feasibility in developing countries depends on hydrogen-supply costs and infrastructure readiness. The Ministry of Energy has reported a 400% increase in imported natural-gas costs due to current geopolitical tensions between the United States and Iran, exposing the strategic vulnerability of relying on imported diesel for public transport. This study assesses the operational hydrogen demand, fuel-cost implications, and avoided diesel tailpipe carbon dioxide (CO₂) emissions associated with gradually integrating FCEBs into Jordan’s Bus Rapid Transit (BRT) project. The baseline system consists of 64 diesel buses covering about 11 million kilometers annually, consuming around 3 million liters of diesel and emitting roughly 8108.3 tons of CO₂. Fleet transition scenarios are assessed for 2030, 2035, and 2040, with FCEB-integration ratios of 10%, 15%, and 25%. Under the reference assumption of equivalent-duty replacement, avoided diesel tailpipe CO₂ emissions increase with the diesel service displaced by FCEBs, reaching 25.7% at the highest penetration level. At the $6/kg reference hydrogen-price input, FCEB integration results in higher operational fuel costs than diesel-only operation. Under the constant diesel-price reference, mixed-fleet operation becomes cost-competitive at hydrogen prices of $1/kg and $2/kg, with operational fuel-cost savings of up to 16.97%. Within the operational fuel-cost boundary of this study, mixed-fleet competitiveness is influenced by both the assumed hydrogen fuel price and diesel-price trajectory. The results support gradual deployment, subject to the greenhouse-gas intensity of the hydrogen-production and delivery pathway and the readiness of hydrogen supply and depot infrastructure. Full article

The increasing generation of textile cotton waste (TCW) and textile wastewater sludge (TWS) presents significant environmental management challenges. This study evaluates the conversion of TCW and TWS into biofuel pellets for waste recovery and coal substitution. Pellets were prepared at TWS ratios of 20:80, 40:60, 60:40, and 80:20 and assessed through combustion emission analysis, ash characterization, cradle-to-gate carbon assessment, and equal-energy cost comparison with imported bituminous coal. Increasing the TWS fraction prolonged combustion duration and increased SO₂ and NO_x emissions; however, all oxygen-normalized emissions remained within Sindh Environmental Quality Standards (SEQS) limits under the tested conditions. The 20:80 blend exhibited the lowest emission factors, with CO, SO₂, NO_x, and CO₂ emissions of 1.03 g kg⁻¹, 3.81 g kg⁻¹, 1.57 g kg⁻¹, and 1.42 kg kg⁻¹, respectively. Ash analysis showed that Cd and Pb were not detected, while measured heavy-metal concentrations remained below U.S. EPA regulatory limits and relevant EU limit values. The 20:80 pellet achieved a cradle-to-gate carbon intensity of 6.6 g CO₂e MJ⁻¹, approximately 59% lower than upstream coal production. Equal-energy fuel-cost savings relative to imported coal were 37.6% for the binder-based 20:80 pellet and 83.1% for the binder-free 40:60 pellet. Overall, the results indicate that TCW–TWS pellets, particularly those containing 20–40% TWS, can support textile waste utilization and partial coal substitution while reducing fuel costs. Full article

Passive solar shading must balance energy saving, daylight availability, glare control, and thermal comfort under contrasting climates. This study develops and validates a lightweight, interpretable light-thermal-energy coupling framework for early-stage shading optimization in building retrofits and new construction. It addresses two questions: how shading geometry, envelope performance, and thermal inertia should adapt to hot low-latitude and cold high-latitude regions, and how their coupled performance can be quantified. The framework combines solar geometry, the Perez radiation model, surface irradiance calculation, indoor ray tracing/voxel illuminance simulation, daylight glare probability (DGP) assessment, and a 6R3C (6-Resistance, 3-Capacitance) transient thermal network. A full-factorial matrix of 120 design combinations was evaluated using shading scale, glazing performance, envelope thermal resistance, and thermal mass as variables, with energy use, thermal response, daylight availability, and DGP as objectives. Results show climate-dependent thermal inertia: it stabilizes indoor temperature in cold regions but increases heat accumulation in hot regions. The optimal schemes satisfy visual comfort (DGP < 0.40) and achieve energy savings up to 44.2% for retrofits and 50.0% for new buildings in hot regions, and 14.6% in cold regions. The framework provides transparent decision support for climate-adaptive, low-carbon building design and complements EnergyPlus, TRNSYS, and Radiance. By supporting energy-efficient retrofits and climate-responsive new construction, the proposed approach contributes to sustainability by reducing dependence on mechanical heating and cooling, improving operational resource efficiency, and maintaining indoor thermal and visual comfort. Full article

Existing urban residential buildings contribute substantially to operational energy use and carbon emissions in the building sector, making low-carbon retrofitting a key approach to improving the performance of the existing housing stock. This study conducts a bibliometric and systematic review of research on low-carbon retrofitting of existing urban residential buildings in China. Journal articles published between 2015 and 2025 were retrieved from Web of Science and Scopus, and 91 studies were retained after screening. Bibliometric analysis was used to examine annual publication trends, source distribution, keyword co-occurrence, thematic evolution, and organizational collaboration. The systematic review further synthesised evidence on retrofit policies, technical measures, and performance evaluation methods. The results indicate a clear increase in publications in recent years, with research attention shifting from basic energy-saving measures towards multi-objective optimization, carbon reduction, and thermal comfort improvement. The review suggests that China’s residential retrofit policies can be understood as a multi-level framework supporting retrofit implementation. Retrofit strategies have gradually shifted from individual measures towards integrated retrofit packages, while performance evaluation has expanded from energy-saving assessment to broader considerations of carbon emissions, occupant comfort, and economic feasibility. The review highlights the need for more consistent evaluation boundaries, stronger integration of lifecycle carbon accounting and occupant behaviour, and climate-responsive retrofit strategies. These findings provide a structured basis for comparing retrofit approaches, strengthening the connection between policy and technology, and supporting decision-making in large-scale residential retrofit programmes. Full article

Amid the escalating challenges of global climate change, promoting the sustainable and low-carbon transformation of wastewater treatment systems has become a critical pathway toward achieving carbon neutrality and sustainable urban infrastructure development. However, existing low-carbon technologies for wastewater treatment still lack systematic and sustainability-oriented evaluation approaches, which constrains the scientific selection of technologies and the optimization of low-carbon transition pathways. In this study, a comprehensive inventory of 30 low-carbon technologies was established across five categories, including equipment energy saving, process improvement, intelligent control, energy recovery, and resource recycling. Based on three dimensions, namely carbon reduction potential, economic performance, and technology readiness level, a Carbon Reduction–Economy–Technology Coupling Index (CRETCI) was developed to enable systematic quantitative evaluation and sustainability-oriented assessment of low-carbon technologies in wastewater treatment systems. The analysis of carbon reduction potential indicated that process improvement technologies exhibited the highest average carbon reduction potential, reaching approximately 0.136 kg CO₂e/m³, demonstrating significant advantages in deep emission reduction. Economic analysis revealed that energy recovery technologies showed the best economic performance, with all marginal abatement costs being negative, indicating strong synergistic benefits between economic returns and carbon mitigation. The technological maturity assessment demonstrated that both intelligent control and energy recovery technologies achieved a Technology Readiness Level (TRL) of 9, indicating a well-established foundation for engineering application. The TCECI evaluation results showed that energy recovery technologies achieved the highest comprehensive score (0.71), significantly outperforming process improvement technologies (0.57). This finding suggests that the current low-carbon technology system for wastewater treatment is characterized by a structural trade-off between high carbon reduction potential and high technological maturity. Overall, this study establishes a multidimensional sustainability evaluation framework integrating environmental benefits, economic feasibility, and technological applicability, thereby providing important theoretical support and practical decision-making guidance for sustainable wastewater management, low-carbon technology selection, and carbon-neutral transition pathway optimization in the wastewater treatment sector. Full article

Achieving carbon neutrality toward 2050 requires not only the adoption of renewable energy technologies but also long-term planning based on their gradual integration into urban systems. This study presents a novel scenario-based framework that quantifies year-by-year impacts of deploying rooftop photovoltaics (PVs), electric vehicles (EVs), and Vehicle to Home (V2H) systems from 2018 through 2050. Five key dimensions are assessed: CO₂ emission reduction, cost savings, self-consumption, energy sufficiency, and self-sufficiency. Using Suita City, Japan, as a case study, we analyzed two diffusion scenarios, “baseline (current growth case)” and “accelerated deployment case”. The results indicate that despite high initial investment, an accelerated scenario can achieve up to a 60% CO₂ emission reduction and over 25% cost savings by 2050. Importantly, the integrated deployment of PVs, EVs, and V2H surpasses PV-only systems in overall effectiveness from around 2035 onward. By capturing the dynamic evolution of technology impacts over time, this study provides unique and actionable insights for designing data-driven policies supporting long-term urban decarbonization. Full article

Reducing carbon emissions while carrying out urban renewal has put existing residential buildings in the spotlight for low-carbon transformation. These buildings typically consume large amounts of energy and offer significant savings potential, making them a priority in the building sector. Addressing the challenges of limited capital, long payback periods, and inadequate comprehensive benefit assessment in building energy retrofits, this study introduces a carbon trading mechanism and develops a priority decision-making framework based on life-cycle cost–benefit analysis and net present value rate (NPVR). Five typical retrofit measures (grouped into four simulation categories), including external wall insulation, roof insulation, window replacement, lighting upgrade, and rooftop photovoltaic (PV) system, are evaluated through TRNSYS energy simulation applied to an aging residential building in Xi’an, China. The results demonstrate that lighting system upgrades and rooftop PV installation yield the highest economic returns and investment efficiency, while building envelope insulation measures, despite delivering substantial energy savings, exhibit lower NPVR due to high initial investment. Sensitivity analysis reveals that electricity price is the dominant factor influencing economic viability, whereas carbon price under current market conditions exerts limited influence on retrofit prioritization. The proposed framework provides a quantitative decision-support tool for building owners and policymakers to optimize retrofit investment strategies under budget constraints. Full article

Existing residential buildings constructed under earlier thermal-design standards often lack effective external solar control systems. Building envelope retrofits must extend beyond mere cooling load reductions; instead, they require a holistic evaluation of summer heat rejection, winter solar gain preservation, transmitted solar exposure, and retrofit-induced embodied carbon. This study develops a screening-level method for climate-adaptive passive shading retrofits. The workflow integrates hourly solar-position reconstruction, facade irradiance mapping, shading geometry interception, and a reduced-order 2R2C thermal network. NSGA-II is used to generate Pareto-optimal alternatives, CV-TOPSIS is applied to identify representative trade-off solutions, and a life-cycle-informed carbon payback check within an A1–A4 + B6 boundary is used to test whether operational carbon savings can offset the upfront carbon of shading components and glazing replacement. Five Chinese cities—Haikou, Shanghai, Beijing, Lhasa, and Urumqi—are selected to represent the transition from cooling- to heating-dominated climates. For comparative screening, the reduced-order model shows acceptable agreement with an EnergyPlus benchmark, with NMBE, CV(RMSE), and $R^2$ values of +2.11%, 28.25%, and 0.804, respectively. The selected solutions reveal strong climate dependence in both shading morphology and carbon performance. For instance, Haikou exhibits the largest annual electricity savings (2030.3 kWh/yr) and the shortest Carbon Payback Period (1.8 years). In Lhasa, by contrast, the CV-TOPSIS-selected compromise scheme reduces the transmitted solar exposure proxy but increases annual energy use by 706.1 kWh/yr, indicating that this selected compromise, rather than fixed shading in general, is not carbon-effective within the defined boundary. The proposed method supports climate-specific retrofit screening by jointly considering heating–cooling balance, solar radiation conditions, and regional grid carbon intensity. Full article

Green hydrogen is commonly assessed as a renewable fuel or long-duration storage option, but its value as a critical-load restoration resource remains less developed, particularly when produced from curtailed renewable electricity. This study develops a planning-oriented framework to assess green hydrogen for critical-load restoration by linking renewable curtailment, proton-exchange membrane electrolysis, hydrogen storage, fuel-cell reconversion, critical Energy Not Served (ENS) reduction, economic valuation, and carbon-footprint savings. The framework is applied to the Dominican Republic power system as a representative insular case with rapid renewable expansion and limited flexibility. Using monthly preliminary real-operation reports from OC-SENI, the reference case considers 196.46 GWh/year of curtailed non-conventional renewable electricity in 2025, producing 3.78 kt H₂/year and 65.5 GWh/year of recoverable electricity. Under the reference screening assumptions, a 25 t H₂ storage module would provide 433.29 MWh of usable electricity, fully covering 6 h and 12 h restoration windows for the 30 MW illustrative critical-load case and reducing critical ENS by 60.2% during a 24 h event. The recovered electricity could avoid 43.5 ktCO₂/year under the SENI combined-margin grid-displacement case, with higher avoided operational emissions under the diesel-backup displacement sensitivity. Full article

Surface congestion and taxiing delays at high-density airports increasingly constrain aviation sustainability, as ground-phase fuel consumption and emissions constitute a significant share of total airport emissions. Existing studies typically decouple air traffic flow management from ground resource scheduling, hindering coordinated optimization of punctuality, environmental benefits, and resource utilization. This paper proposes a multi-objective optimization method for runway-taxiway systems oriented toward air–ground collaborative decision-making, integrating Calculated Take-Off Time (CTOT) compliance constraints. A tri-objective mixed-integer programming model is formulated to minimize CTOT deviation, total taxiing time, and runway workload imbalance. A hybrid intelligent algorithm, SSA-SCA-NSGA-II, is designed with a bidirectional elite feedback mechanism to address this NP-hard problem. Validation uses real operational data of 58 departure flights during a peak period at Beijing Daxing International Airport. The results demonstrate that the proposed method achieves effective trade-offs on the Pareto front: CTOT compliance rate increased from 77.6% to 89.7–96.6%; total taxiing time decreased from 692 min to 551–635 min; and dual-runway utilization imbalance declined from 5.2% to 1.7–3.8%. These improvements translate into quantifiable sustainability gains: fuel consumption is reduced by 1425–3525 kg and CO₂ emissions by 4503–11,139 kg per peak hour, alongside a 19-percentage point improvement in punctuality that lowers passenger delay costs and reduces controller coordination workload. By simultaneously advancing environmental sustainability (carbon footprint reduction), economic sustainability (fuel and operational cost savings), and social sustainability (service punctuality and labor efficiency), the framework provides a measurable, monitorable, and policy-relevant decision-support tool for green airport surface operations aligned with sustainable development goals (SDGs). Full article

Urban plant communities are widely regarded as important nature-based solutions for climate mitigation, yet their actual carbon benefits remain uncertain: vegetation growth is accompanied by carbon emissions from construction and long-term maintenance, and existing assessments rarely integrate community succession, interspecific competition, and maintenance-related emissions within a consistent life-cycle framework. To address these limitations, this study developed a dynamic succession-based life-cycle simulation model to project the 50-year carbon source–sink transitions of 150 typical urban plant communities in Tianjin, China. The model updates plant structural attributes—diameter at breast height, crown width, and tree height—iteratively by linking individual plant growth to environmental suitability and neighborhood competition through a Plant Health Index. Simulated structural trajectories were coupled with biomass equations and carbon content coefficients to estimate aboveground carbon sequestration, while construction and maintenance emissions were quantified using life cycle assessment, enabling evaluation of modeled net carbon balance rather than gross carbon sequestration alone. Under the modeled 50-year scenario, most communities were projected to act as carbon sources during the early stage but gradually shifted toward carbon sinks as biomass accumulated; 86.1% of the communities were projected to become net carbon sinks after 50 years (a scenario-based projection under specified growth, maintenance, and emission assumptions). The highest modeled net carbon balance reached 3186.08 kg·C·ha⁻¹, whereas the weakest community remained a slight carbon source at −81.21 kg·C·ha⁻¹. Vertical structural complexity and species richness were the strongest positive predictors of modeled net carbon balance, followed by three-dimensional green quantity and canopy closure. Among maintenance processes, fertilization was the dominant emission source, followed by pesticide application and irrigation; comparative scenario analysis showed that resource-saving maintenance consistently improved projected net carbon balance relative to high-maintenance management. These results suggest that low-carbon planting design should prioritize locally adapted species, multi-layered vertical structures, and adaptive maintenance over simply maximizing planting density or minimizing inputs. The results represent scenario-based projections of aboveground vegetation carbon balance; belowground biomass, soil carbon, litter carbon, dead organic matter, and parameter uncertainty were not fully incorporated, and future studies should address these limitations to improve the robustness and transferability of the proposed framework. Full article

Raising indoor temperature setpoints is widely promoted as a practical way to reduce cooling-related energy demand in commercial buildings, yet its net carbon impact becomes uncertain once behavioral rebound effects are considered. This study develops an integrated carbon-accounting framework to evaluate the climate implications of summer indoor temperature increases of 1–3 °C in U.S. mercantile buildings. The framework combines operational energy savings from reduced cooling demand with consumption-driven emissions arising from longer customer dwell times and increased consumer spending under improved thermal comfort conditions. Carbon outcomes are quantified using sector-level electricity data and the USEEIO emission factor for retail trade. The results reveal a clear imbalance: operational carbon savings range from 0.21 to 0.64 Mt CO₂, whereas consumption-driven emissions range from 3.37 to 21.90 Mt CO₂, yielding a consistently positive net carbon impact of 3.16–21.26 Mt CO₂ across all scenarios. A break-even analysis indicates that only 1.30–3.89 billion USD in additional spending is sufficient to offset the operational savings. The findings remained robust across alternative behavioral and carbon-accounting specifications; a 10,000-iteration Monte Carlo analysis produced positive net carbon impacts in every simulation (median 8.54 Mt CO₂; P(NCI > 0) = 1.00). Overall, the results suggest that temperature-based efficiency measures may overstate their climate benefits when behavioral responses are ignored, highlighting the importance of incorporating rebound effects into building energy assessments and commercial climate policy. Full article

Building energy consumption accounts for a significant proportion of total societal energy consumption, and reducing building energy consumption is critical to the global mission of reducing emissions. Windows are regarded as the least energy-efficient component of a building’s envelope. This study examines service-area buildings fitted with high-performance glass in Chinese cities across various climates and employs the non-dominated sorting genetic algorithm II (NSGA-II) genetic algorithm for multi-objective optimization. In considering design variables such as building orientation and wall insulation, advanced passive design strategies, including electrochromic and aerogel glass, are incorporated into the optimization process to minimize construction costs and operational carbon emissions. Sensitivity analyses were conducted to evaluate the impact of each design variable on building operational carbon emissions. The optimal solution within the Pareto optimal set was further evaluated using the technique for order preference by similarity to ideal solution (TOPSIS) decision-making method, and the preferred energy-saving solution was quantitatively analyzed. The results indicate that optimization leads to a reduction of approximately 7.70–10.50% in annual operational carbon emissions for service-area buildings across different regions, compared to the base case, with a payback period ranging from 4.90 to 13.56 years. The proposed method contributes to sustainable building design by jointly quantifying carbon-emission reduction, construction cost, and payback period, thereby supporting climate-responsive and economically feasible low-carbon envelope decisions for service-area buildings. Full article

Energy-intelligent building control is widely advocated as a key strategy for reducing building energy use and associated carbon emissions. However, empirical evidence from real buildings remains relatively scarce and is often affected by methodological limitations. This study reports a 92-day field experiment on the 14th floor of an office building in Shenzhen, China, where an Internet of Things (IoT) and edge-computing-based intelligent building environmental control system was deployed to manage lighting and HVAC. An A-B-A experimental design was implemented in summer 2022, comprising two intelligent-control phases (A₁ and A₂, July and September) and one intermediate manual-control phase (B, August) during which the intelligent algorithms were disabled without notifying occupants. Aggregated monthly runtimes show average energy-saving potential ratios of approximately 25.98% for lighting and 19.50% for HVAC when the intelligent system is active. As this study was conducted on a single office floor in one building, the results should be interpreted as proof-of-concept field evidence for this specific operational and climatic context rather than as directly generalizable performance estimates for all office buildings. The study further highlights methodological considerations for future field evaluations, including the influence of outdoor climate, occupancy patterns and experimental design choices. The findings provide a real-world empirical case of the energy-saving potential performance of intelligent environmental control in office buildings and contribute to narrowing the gap between simulated and measured savings. Full article