Search Results (508)

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

Microalgal lipid extraction, particularly the subsequent solvent recovery phase, constitutes the primary energy bottleneck in algal-based biodiesel biorefineries. Recently, switchable polarity solvents (SPS), such as the tertiary amine N,N-dimethylcyclohexylamine (DMCHA), have emerged as promising ‘green’ alternatives capable of extracting lipids directly from wet biomass, theoretically bypassing energy-intensive drying and solvent recovery distillation stages. This study presents a rigorous techno-energetic and thermodynamic evaluation combined with supporting experiments for qualitative conclusions to scrutinize the actual viability of DMCHA-mediated extraction against conventional hexane benchmarks, across three process configurations using different biomass types: algal liquor, wet paste, and dried biomass. Contrary to widespread assumptions in the literature, fundamental thermodynamic calculations reveal that the energy required for amine regeneration via protonation/deprotonation mechanisms equals or exceeds that of conventional distillation. Furthermore, mitigating biomass drying inadvertently escalates overall downstream energy and economic penalties due to the excessive solvent volumes demanded by dilute aqueous matrices. Direct extraction from algal liquor displays a cost and energy consumption countably higher than the other scenario; precisely, a cost of 232 €/kg of lipids and energy consumption of 454 kWh/kg of lipids. Extraction from wet paste exhibits, indeed, a slightly lower energy consumption compared to the hexane process (respectively 51 kWh/h versus 72 kWh/kg), but, due to the CO₂ requirements, the cost is double (19 €/kg of lipids versus 8 €/kg of lipids). Ultimately, while switchable polarity chemistry offers a marginal reduction in process water footprints, it introduces substantial operational complexity, elevated carbon dioxide payloads, and severe solvent degradation risks, challenging its current readiness for industrial upscaling. Full article

This study evaluates the economic and carbon footprint impact of using calcium lignosulfonate (CLS) in stabilizing highway subgrade on road pavement. Specifically, the effect of stabilized soil strength on layer thickness, costs, and carbon emissions during the initial construction phase was investigated. Two different soil types (clayey and sandy) were used with varying CLS concentrations. Furthermore, the performance of CLS was evaluated using sodium hydroxide-based alkaline activation (AAS). Standard proctor, unconfined compressive strength (UCS), and California bearing ratio tests were applied to the prepared samples. The experimental results showed that CLS significantly increased the CBR and UCS values of the soil samples. Additionally, it was calculated that the initial construction costs of flexible and rigid road pavements designed on stabilized clayey soil decreased by 14.34% and 25.24%, respectively, while on sandy soils, the decreases were 8.10% and 14.95%, respectively. Meanwhile, it has been determined that CO₂ emissions were reduced by up to 10.76% in flexible pavement designs and by up to 17.88% in rigid pavement designs. Consequently, these findings show that the use of CLS in soil stabilization enables both a reduction in the layer thickness of road pavement designs and a reduction in environmental impacts. Full article

Background: The research question explored in this study revolves around the quantitative evaluation of the carbon footprint of cranioplasty surgery, a neurosurgical intervention meant to reconstruct skull defects. Methods: Following a calculation of the emissions pertaining to Scope 1 to 3 of the Greenhouse Gas (GHG) Protocol, the authors engaged with various stakeholders to identify possible interventions meant to drive the carbon efficiency of a cranioplasty pathway. The service improvement project (SIP) that ensued was aimed at reducing the volume and weight of the packaging materials for cranioplasty shipping boxes, and decreasing the paper consumption relative to the preparation of user manuals without compromising patients’ safety. Results: Our analysis indicates a cumulative carbon footprint of 104.35 kg CO₂e for a single unilateral cranioplasty operation, where packaging corresponds to 6.4% of Scope 3 emissions and 1.41% of its total emissions. Of note, our SIP led to an overall 76.53% decrease in the number of emissions generated by the packaging equivalent required for a unilateral titanium implant. Conclusions: This study demonstrates the effectiveness of a partnership between public institutions and medtech companies in driving carbon net efficiency of a cranioplasty pathway, and we suggest that such approach is scalable to other surgical specialties. Full article

This paper presents an exploratory operational assessment of the carbon footprint of an LNG tanker using real operational data collected by a continuous emission monitoring system over a ten-month period of vessel operation. The analysis included carbon dioxide (CO₂) and methane (CH₄) emissions from the main engines and diesel generators, the calculation of CO₂-equivalent using the GWP₁₀₀ and GWP₂₀ global warming potential factors, and a comparison with a hypothetical heavy fuel oil (HFO) operating scenario. The methodology is based on a Tier III approach, that is, on real operational data, which allows a more realistic assessment of emissions than approaches based on standard emission factors. The results show that CO₂ emissions make up the largest share of total emissions, but including methane emissions significantly increases the ship’s overall climate impact. Total methane slip was 3.62%, with diesel generators exhibiting higher slip than the main engines. When GWP₂₀ was applied, total emissions expressed as CO₂-equivalent were, in some periods, comparable to or higher than those estimated for the HFO scenario, despite lower direct CO₂ emissions. The emission distribution indicated that the main engines dominated CO₂ emissions, while methane emissions were more evenly distributed between the main engines and the auxiliary generators, with generators making a significant contribution to total CO₂-equivalent emissions due to their higher methane slip. The results confirm that any assessment of the climate performance of LNG-fueled operation must include methane emissions and should be based on real operational data; otherwise, the overall climate impact may be underestimated. Full article

Background/Objectives: Animal-source protein consumption in Saudi Arabia has increased substantially over the last two decades, raising concerns regarding its environmental impact in a country with among the highest per capita carbon emissions globally. Despite growing interest in sustainable diets, empirical evidence on dietary carbon footprint (CF) in Gulf Cooperation Council countries remains limited. This study aimed to quantify the CF associated with the consumption of animal- and plant-based protein foods among Saudi adults and to identify sociodemographic and lifestyle predictors of dietary CF, with attention to sex differences. Methods: A cross-sectional study was conducted among 1624 Saudi adults (47.1% males; 52.9% females). A newly developed, expert-reviewed, and pilot-tested food frequency questionnaire covering 21 protein-containing food items (13 animal-based; 8 plant-based) was used to estimate daily intake. CF values were calculated using Life Cycle Assessment-derived greenhouse gas emission factors (kgCO₂e/kg food) obtained from peer-reviewed sources. Sex-stratified multiple linear regression models and a pooled sex × animal-source protein food interaction model was used to identify independent predictors of daily CF. Results: Animal-source protein foods contributed 45,641.8 kgCO₂e/week to cumulative CF—a 64-fold excess over plant-based sources (708.33 kgCO₂e/week). Mean individual protein-food CF was 4.07 kgCO₂e/day, of which 98.5% derived from animal sources. Lamb and beef carried the highest emission intensities; nuts the lowest. Animal-source intake was the strongest independent predictor of CF in both sexes, with a significantly stronger association in males than females. High consumers substantially exceeded EAT–Lancet red meat targets across all consumption strata. Conclusions: Red meat dominates protein-food-related GHG emissions among Saudi adults. Even a partial dietary shift toward plant-based proteins, embedded within a coordinated food-system transformation framework, could substantially reduce per capita emissions in alignment with Saudi Vision 2030 and One Health targets. Full article

The application of urea in agricultural practices leads to carbon dioxide (CO₂) emissions through hydrolysis. Urea, when applied to soil, reacts with water and undergoes hydrolysis, releasing ammonia (NH₃) and CO₂. This reaction is facilitated by soil enzymes such as urease. The released NH₃ can further undergo nitrification, producing nitrate (NO₃⁻) and nitrous oxide (N₂O). While CO₂ from urea hydrolysis is relatively small compared to other sources, cumulative emissions from agricultural activities contribute significantly to climate change and agriculture’s carbon footprint. A straightforward calculation model (CO₂ = A × 0.73) was employed to approximate CO₂ emissions in various countries based on annual urea usage. In this model, China led emissions with 40,483 Gg yr⁻¹, followed by India (26,031 Gg yr⁻¹) and the USA (12,032 Gg yr⁻¹). Out of total annual emissions (94,763 Gg), China contributed 43%, India 27%, the USA 13%, the EU 8%, Pakistan 5%, and Indonesia 4%. China’s CO₂ emissions from urea were 16% higher than India, 30% higher than the USA, 35% higher than the EU, 38% higher than Pakistan, and 39% higher than Indonesia. As expected from the deterministic IPCC formula (CO₂ = Urea × 0.73), the relationship between urea consumption and CO₂ emissions is linear with a slope of 0.73. Linear regression shows that for every 1000-ton increase in urea consumption, CO₂ emissions increase by 730 tons (0.73 Gg) (R² = 0.99, p < 0.001). Pakistan’s urea consumption grew at an average annual rate of 2.2% from 2015 to 2023, with corresponding CO₂ emissions increasing from 4015 to 4788 Gg yr⁻¹ (total increase of 20% over eight years). Optimizing fertilizer application rates, timing, and methods to enhance nutrient uptake efficiency, along with sustainable agricultural practices (organic matter management, conservation tillage, and precision agriculture), can help mitigate environmental impacts. This study emphasizes implementing sustainable agricultural practices and integrated nutrient management to minimize CO₂ emissions from urea application, enabling agricultural systems to contribute to climate change mitigation and reduced carbon footprints. Full article

Against the backdrop of global climate change and the “dual carbon” goals, the issue of agricultural greenhouse gas emissions has garnered increasing attention. As a major grain and oilseed crop in China, carbon emissions from soybean production have a significant impact on the green and low-carbon development of agriculture. Although research on agricultural carbon footprints has grown in recent years, existing studies have largely focused on single regions or specific stages of crop production, and analyses of the carbon footprint of production systems in China’s major soybean-producing regions remain relatively limited. This study employs the Life Cycle Assessment (LCA) methodology to calculate and analyze the carbon footprint of soybean production systems across China’s 10 major soybean-producing provinces, utilizing agricultural input data from 2014 to 2023. The study establishes a carbon footprint accounting system based on two key aspects: carbon emissions from agricultural inputs and soil N₂O emissions. It further analyzes the temporal trends, regional variations, and contribution characteristics of each component within the carbon footprint. The results indicate that the average carbon footprint of soybean production in China is approximately 528 kg CO₂eq/ha (ranging from 273 to 855) and 0.25 CO₂eq/kg of soybean (ranging from 0.13 to 0.46). Specifically, the carbon footprint per unit of area and yield declined simultaneously, indicating a continuous improvement in the low-carbon efficiency of soybean production. Spatially, there are significant regional differences in the carbon footprint of soybean production. Henan, Anhui, and Inner Mongolia have relatively low carbon footprints, while Shaanxi and Shanxi have relatively high levels. In terms of composition, chemical fertilizer inputs and soil N₂O emissions are the primary sources of the carbon footprint in soybean production, with chemical fertilizer inputs being the largest source, accounting for approximately 40–60%, and soil N₂O emissions being the second major source. Overall, differences among regions in natural conditions, agricultural input structures, and production methods result in distinct regional characteristics in the carbon footprint composition. The findings of this study provide a scientific basis for the low-carbon transition of China’s soybean production system and serve as a reference for the formulation of policies related to green agricultural development. Full article

Parking infrastructure is an important yet often inconsistently treated element in whole-life carbon footprint assessments and broader building sustainability evaluation. With the revised Energy Performance of Buildings Directive (EPBD) introducing mandatory global warming potential (GWP) reporting, the influence of methodological choices on GWP results requires a clearer understanding. This study examines six multi-apartment residential (MAR) projects featuring four distinct parking typologies to quantify how parking infrastructure affects calculated GWP outcomes. Using EN 15804-compliant life cycle assessment (LCA) data, we evaluate four methodological approaches for including parking infrastructure in GWP calculations and the approach mandated by the delegated act supplementing the EPBD (DA-EPBD). The results show that parking infrastructure can account for up to 39% of embodied and up to 25% of whole life cycle emissions. Methodological approaches significantly influenced the GWP results, leading to differences of up to 32% in sample median values. An inconsistency in the DA-EPBD approach is identified, resulting in better GWP performance for projects including large-area attached parking infrastructure, while leading to higher GWP values for projects with detached parking. The findings highlight the sensitivity of GWP outcomes to methodological assumptions regarding parking infrastructure and underscore the need for clear national GWP calculation rules when integrating DA-EPBD requirements. Full article

To quantify the carbon footprint of cross-border bridges built by Chinese companies in Africa, based on the Janwani Bridge in Tanzania and the life cycle theory, it is divided into five stages: production, transportation, on-site construction, operational maintenance, and demolition and disposal. Using the emission factor method to construct carbon emission models for each stage, while considering cross-border supply chains and the addition of vegetation carbon sinks, we quantify the emissions for each stage. The research is based on the project design stage bill of quantities and construction organization data for prediction and estimation. The energy consumption parameters of construction machinery refer to the Chinese quota standards, and the energy consumption of lighting during the operation period is estimated according to the design parameters. The results show that the total carbon emissions of the life cycle of the bridge is about 41,668,548.20 kgCO₂e, with the production stage being the dominant position (87.48%), and cement and reinforcing steel contributing more than 95% of the emissions during this stage. The operational maintenance stage comes second (7.28%), mainly driven by lighting electricity (accounting for 73.65% of the total emissions in this stage), attributed to the local power grid dominated by fossil fuels. Sensitivity analysis shows that the key factors are ranked as cement > reinforcing steel > electricity > diesel. Considering the reality of insufficient supply of low-carbon materials and weak infrastructure in Africa, emission reduction measures are proposed from three aspects: optimizing concrete mix proportion, controlling construction machinery, and implementing intelligent lighting. The research contribution lies in incorporating the entire cross-border transportation chain and newly added vegetation carbon sinks into the LCA boundary of bridges, while considering the dual attributes of “technology output + localized operation”, and constructing a carbon emission accounting model adapted to the built-up areas of African cities. On this basis, the carbon emission characteristics of the life cycle were quantitatively analyzed, feasible emission reduction measures in the region were proposed, and the carbon reduction potential was calculated, providing scientific basis for low-carbon control of Chinese enterprises’ overseas bridges. Full article

With the increasing penetration of wind power, enhancing the renewable energy accommodation rate and reducing the carbon footprint of the IES, this study proposes a comprehensive evaluation method to assess the impact of a novel dynamic Green Certificate Trading (GCT) and Green Hydrogen Certificate Trading (GHCT) joint mechanism. First, considering the integration of the IES into the carbon trading market, a coupled dynamic GCT-GHCT framework is established. This framework links dynamic green electricity certificate revenues with green hydrogen certificate revenues, leveraging cross-subsidization to incentivize renewable energy consumption. Subsequently, an optimal operation model for the IES is formulated with the objective of minimizing comprehensive costs, which encompass energy procurement, green certificates, carbon trading, and wind curtailment penalties. A piecewise linearization approach is applied to transform the optimization model into a Mixed-Integer Linear Programming problem for efficient solving. Furthermore, based on the dispatch results, a multidimensional evaluation index system is constructed, extracting key indicators from economic, technical, and environmental perspectives. To ensure the rationality of the evaluation, a dynamic reward–penalty asymmetric cloud matter-element (ACME) comprehensive evaluation method based on game theory combinatorial weighting is introduced to calculate the index weights and the final comprehensive evaluation value. Finally, multi-scenario simulations are conducted to verify the superiority of the integrated GCT-GHCT trading framework. The results reveal that the proposed approach not only maximizes renewable energy integration but also provides a robust decision-making tool for the low-carbon transition of multi-energy systems. Full article

Life Cycle Assessment (LCA) is extensively employed to support sustainability evaluation in waste management and manufacturing systems; however, outcomes are highly sensitive to methodological decisions, particularly end-of-life (EoL) allocation approaches. This study examines how cut-off and substitution approaches affect the energy performance and decarbonisation potential of high-density polyethylene (HDPE) injection moulding systems. A dual framework is adopted: first, a literature review examines methodological sensitivities in EoL modelling; second, a quantitative case study assesses industrial-scale primary data for the production of durable HDPE bottles (300 mL). The LCA model integrates specific technical parameters, including a 220 °C melt temperature and a 36 s cycle time, ensuring a realistic representation of manufacturing conditions. The results indicate that allocation choices significantly influence calculated impacts, sometimes reversing the relative ranking of configurations. Substitution-based approaches report higher benefits by crediting avoided primary production, while cut-off logic provides more conservative estimates. Quantitative analysis shows that transitioning from open-loop to fully closed-loop configurations reduces cumulative energy demand by 3.2% and freshwater emissions per functional unit by 2.8%. Furthermore, the study identifies a ‘landfill paradox’ specific to HDPE waste within transitional energy systems: due to the carbon sequestration effect of landfilled polymers and current grid emission factors, landfilling exhibits a lower net carbon footprint (0.03 kg CO₂-eq./kg) than high-efficiency incineration (1.54 kg CO₂-eq./kg). These findings highlight that circular economy evaluations are strongly shaped by methodological assumptions, with direct implications for energy policy. Bridging the gap between specific industrial processing parameters and end-of-life allocation logic underscores the need to incorporate primary industrial data and transparent allocation frameworks to support reliable decision-making in the transition toward low-carbon and energy-efficient manufacturing systems. Full article

The construction sector is a major consumer of raw materials and a significant source of greenhouse gas emissions, necessitating data-driven approaches to support circular economy implementation and sustainable project management. This study develops an integrated framework combining machine learning-based material stock prediction, carbon footprint assessment, and Environmental, Social, and Governance (ESG) performance evaluation for construction projects. A dataset of 128 residential buildings was compiled from official use-permit documentation. After dimensionality reduction using variance filtering and Spearman correlation analysis, 25 regression algorithms were evaluated to estimate quantities of concrete, reinforcement, and brick products. The K-Nearest Neighbor (KNN) Regressor achieved the best predictive performance, with mean absolute percentage errors of 10.64% for concrete, 10.23% for reinforcement, and 16.05% for brick products. Predicted material quantities were used to calculate CO₂ emissions across materialization, demolition, and disposal phases under linear and circular scenarios. The results indicate that circular economy implementation significantly reduces total emissions, particularly for concrete, with reductions of up to 97% under idealized full-substitution conditions, representing an upper-bound estimate. ESG assessment using the Delphi method identified environmental indicators as the most significant sustainability dimension. The proposed framework enables early-stage emission estimation and supports informed decision-making toward low-carbon and resource-efficient construction practices. Full article

Assessing carbon footprints has become increasingly important globally as a key tool for quantifying environmental impacts and supporting sustainable decision-making. However, although allegorical floats—central elements of large-scale parades in internationally recognized cultural festivals such as the Rose Parade in Pasadena, USA (RPP), the Rio de Janeiro Carnival, Brazil (RJC), the Black and White Carnival in San Juan de Pasto, Colombia (BWC), and the Fruit and Flower Festival in Ambato, Ecuador (FFF)—represent significant expressions of cultural heritage and artistic creativity, their environmental impact has received limited attention in sustainability research. The primary objective was to quantify the carbon emissions associated with constructing these temporary structures. The methodology integrated geometric surface estimation with carbon accounting principles commonly applied in life-cycle assessment. Emissions were calculated based on the material composition of the structural, covering, and finishing stages, and normalized using two indicators: kilograms of CO₂ equivalent (kg CO₂e) per square meter of float surface area and kg CO₂e per float. Results indicate that emission intensity varies substantially across festivals, with RJC exhibiting the highest value (approximately 9 kg CO₂e/m²) due to extensive use of synthetic materials, while BWC demonstrates the lowest intensity (approximately 4.3 kg CO₂e/m²) as a result of greater reliance on wood- and paper-based components. When assessed per float, the large scale of RJC structures leads to emissions exceeding 30,000 kg CO₂e per float, whereas FFF floats generate less than 1000 kg CO₂e due to their smaller dimensions and use of natural materials. This research constitutes the first comparative carbon assessment of allegorical float construction and advances the emerging intersection of cultural heritage studies and environmental sustainability. Full article

Silicomanganese slag (SiMnS), a Mn-bearing by-product from silicomanganese alloy production, is often stockpiled in large quantities and may pose environmental concerns due to potential metal leaching. This study develops an OPC-rich hybrid SiMnS–steel slag–fly ash–OPC-activated composite binder, referred to as SMSAB, in which OPC accounts for 55% of the solid precursor mass. Different alkali contents and sodium silicate moduli were investigated, and the optimised paste was characterised in terms of mechanical strength, reaction products, pore structure, carbon-footprint and heavy-metal leaching. The best performance was obtained at an alkali content of 4% and a sodium silicate modulus of 1.0, giving 28-day compressive and flexural strengths of 65.13 MPa and 3.37 MPa, respectively. XRD, SEM-EDS, FTIR and MIP results showed that the main reaction products were C-(A)-S-H, N-A-S-H and C-N-A-S-H gels, which refined the pore structure and produced a dense matrix. The reduction in Mn leaching may be associated with physical encapsulation, possible charge-balancing interactions within gel structures, changes in Mn-related bonding environments and the presence of Mn-bearing phases. Leaching concentrations of Zn, Mn, Cr, Cu and Ni satisfied the Grade III groundwater limits used in China. The calculated carbon intensity of SMSAB was 3.97 kg·(m³·MPa)⁻¹, indicating a favourable strength-to-emission balance compared with the reference systems considered. It should be noted that the present work examines paste specimens only; aggregate skeleton, traffic loading, freeze–thaw cycling and wet–dry/moisture cycling were not included. Therefore, the results demonstrate binder-level potential rather than direct qualification of SMSAB as a pavement base or subbase material. Full article