Search Results (1,271)

The depletion of fossil fuels and the need to valorize agricultural residues motivate biomass-to-electricity pathways coupling gasification with an efficient, low-emission prime mover. This study evaluates four residues—olive pomace (Fuel A), olive tree pruning (Fuel B), date palm seeds (Fuel C), and date pits (Fuel D)—converted into H${}_2$-rich syngas and supplied to a homogeneous charge compression ignition (HCCI) engine. A three-dimensional CFD model with GRI-Mech 3.0 detailed chemical kinetics resolves the in-cylinder combustion of each syngas, supported by a qualitative cross-study physical-consistency comparison against published syngas-HCCI pressure data. Intake temperature, equivalence ratio, and EGR are varied at both fixed equivalence ratio and fixed fuel-energy input per cycle. At fixed $\varphi =0.40$, CA${}_{50}$ remains nearly uniform across the four fuels despite the more-than-twofold variation in H${}_2$/CO, whereas peak pressure differs substantially: steam-gasified date-seed syngases (Fuels C and D; H${}_2$/CO = 1.21–2.00) reach 93–97 bar, compared with 79–83 bar for air-blown olive-residue syngases (Fuels A and B; H${}_2$/CO = 0.76–0.89), though the baseline maximum pressure-rise rate exceeds the adopted engine-damage threshold for all four fuels. Indicated thermal efficiency ranges from 43.2 to 44.4% across the four fuels. CO and UHC emissions are generally lower in the more hydrogen-rich cases, whereas NO${}_x$ varies non-monotonically with fuel composition and operating condition. Combining literature-derived gasification cold-gas efficiencies with the engine results gives an estimated upper-bound biomass-to-electricity efficiency of approximately 26–28% and a base-case LCOE of 0.071 USD/kWh, with combined scenario bounds of 0.025–0.150 USD/kWh, based on adopted techno-economic assumptions and a baseline operating point that would require further mitigation to meet the adopted pressure-rise-rate limit. The results provide a feedstock-resolved basis for assessing agro-industrial residue-to-electricity pathways in decentralized, off-grid applications. Full article

Construction-stage carbon emissions from environmental remediation projects remain poorly quantified despite growing demands for low-carbon infrastructure. This study develops a carbon accounting framework for landfill vertical barrier engineering based on a full-scale remediation project in Haikou, China. Carbon emissions associated with fossil fuel consumption, construction materials, electricity use, water consumption during construction, and personnel-related activities were quantified using the emission factor method, and conventional and intelligent construction scenarios were compared. The results show that fossil fuel combustion accounted for 80.87% of total emissions under the conventional construction scenario and 66.83% under the intelligent construction scenario. Intelligent construction reduced total emissions by 19.34%, accompanied by reductions of 33.3% in diesel consumption, 2.9% in HDPE geomembrane consumption, and 15.5% in construction duration. Equipment electrification, automated construction, and intelligent grouting were identified as the primary drivers of carbon reduction through improved energy efficiency and material utilization. The proposed framework provides practical guidance for low-carbon construction and sustainable landfill remediation. Full article

Reaching net-zero emissions requires more than displacing fossil combustion with renewable electricity; several of the largest industrial emitters—cement, steel, chemicals, and aviation—cannot be fully electrified with current technology, and captured carbon dioxide (CO₂) itself must find a productive destination rather than remain a permanent liability. Converting CO₂ into formic acid (HCOOH) has emerged as one of the more mature answers to that second problem. Formic acid combines a respectable hydrogen content (4.4 wt%), a stable liquid state at ambient conditions, and comparatively benign handling relative to gaseous or cryogenic hydrogen, positioning it as both a chemical feedstock and an energy carrier. This review synthesizes the current state of CO₂-to-HCOOH conversion across thermochemical, electrochemical, photocatalytic, and biocatalytic routes; examines formic acid’s performance as a liquid organic hydrogen carrier (LOHC) and direct fuel-cell fuel; and evaluates the technology through a recently published pilot-scale case study of a photocatalytic reactor, branded RK-X, developed by the author’s employer—presented here as a single illustrative example rather than a representative benchmark—to show both the promise and the unresolved energetic and economic questions still facing the field. We conclude that formic acid-based CO₂ utilization is technically credible and policy-relevant, but that claims of net energy or carbon benefit must be assessed pathway-by-pathway, powered overwhelmingly by low-cost renewable electricity, and confirmed through independent life-cycle assessment before the technology can be considered a settled pillar of the net-zero toolkit. Full article

Achieving sustainable industrial transformation under carbon neutrality constraints requires breaking the high-carbon lock-in of the chemical sector through renewable-based production pathways. Green methanol, produced via CO₂ hydrogenation using green hydrogen and captured industrial CO₂, represents a critical technological option for decarbonizing methanol production while enabling circular utilization of industrial carbon emissions. Existing research on green methanol cost generally treats the CO₂ feedstock cost as a uniform national constant, thereby obscuring the economic heterogeneity of different industrial CO₂ sources and their spatial coupling with provincial renewable resource endowments, which limits the granularity of decision support for regionally differentiated green methanol deployment. This study constructs an integrated sustainability assessment framework for green methanol in China, systematically differentiating four typical post-combustion industrial CO₂ source scenarios—steel, cement, coal-fired power and coal–chemical industries. By integrating the levelized cost of electricity (LCOE) model, green hydrogen production cost accounting, and provincial-level CO₂ capture cost trajectories, the framework forecasts the provincial green methanol production cost across 29 Chinese provinces from 2030 to 2060. The results show that (1) under the four industrial CO₂ source scenarios, China’s provincial green methanol cost declines persistently between 2030 and 2060, with the coal–chemical source achieving the lowest cost (2032–3434 CNY/t) and the coal-fired power source the highest (2168–3565 CNY/t) in 2060. (2) The spatial pattern shows a stable “low costs in the Three-North region and high costs in southeastern and central China” differentiation, with Qinghai, Gansu, Inner Mongolia and Xinjiang positioned below 2500 CNY/t in 2060, reflecting the resource–environment coupling mechanism governing sustainable deployment of renewable-based chemical production. (3) Green hydrogen accounts for 76.4–80.9% of total cost while CO₂ capture accounts for 4.1–10.1%, so that inter-provincial cost spread within any scenario is governed almost entirely by green hydrogen cost, whereas the choice of industrial CO₂ source shifts the cost level of a given province. (4) Traditional industrial provinces such as Hebei and Jilin attain near-term cost competitiveness comparable to northwestern resource-rich provinces by combining locally available low-cost CO₂ sources with a favorable renewable generation mix, though this advantage narrows towards 2060. These findings provide scientifically grounded pathways for China’s sustainable chemical industry transition, supporting the coordinated achievement of industrial decarbonization (SDG 9), climate action (SDG 13), and responsible consumption and production (SDG 12), while offering actionable guidance for spatially differentiated sustainable development policies that maximize economic and environmental co-benefits. Full article

This study presents a 3D computational fluid dynamics (CFD) investigation of methane and methanol combustion in a medium-speed, large-bore marine spark-ignition engine equipped with a pre-chamber (PC) ignition system. Simulations were performed in ANSYS Forte at 100%, 80%, and 20% engine load. Methane operation with an active PC was used as the reference configuration, while methanol was investigated with both active and passive PC. A preliminary injection-timing analysis was conducted for the active methanol configuration to obtain a near-stoichiometric and sufficiently homogeneous mixture inside the PC at spark timing (ST). The results show that active methanol operation promotes earlier heat release, shorter combustion duration, and higher thermal efficiency than methane operation. The active PC generates stronger turbulent reacting jets and ensures more robust combustion than the passive configuration. Methanol also considerably reduces NO_x emissions because of its lower initial and combustion temperatures. However, active methanol operation increases CO emissions, particularly at low load, because of incomplete oxidation associated with low temperatures, mixture inhomogeneity, and possible spray–wall interaction. The passive PC further reduces NO_x and CO emissions but causes delayed combustion, lower thermal efficiency, higher fuel consumption, and tank-to-wake CO₂ emissions than the active methanol configuration. Full article

The global shift toward cleaner energy has positioned hydrogen-enriched methane (CH₄/H₂) as a practical bridge fuel. While it burns more efficiently and produces fewer carbon emissions than traditional hydrocarbons, it introduces operational and safety challenges. Hydrogen’s high reactivity and rapid burning velocity increase risks such as flashback and premature ignition. This study employs Computational Fluid Dynamics to examine the combustion behavior of methane−hydrogen blends in a 2D axisymmetric chamber based on RANS equations. Using ANSYS Fluent 19.1, the research utilizes a validated equilibrium mixture-fraction/PDF framework to ensure accuracy against physical experiments. The simulation framework successfully captures the complexity of non-premixed turbulent combustion by combining a probability density function approach with a realizable k-ε turbulence model. Moreover, this research explores how varying hydrogen concentrations and air mass flow rates, covering the full spectrum from lean to fuel-rich conditions, affect fluid dynamics, turbulence, and the development of recirculation zones. The data show that adding hydrogen fundamentally reshapes velocity fields and thermal profiles, which in turn dictate combustion efficiency and pollutant formation. It has been demonstrated that the optimal blend for combustion performance is the case containing 30% hydrogen. Furthermore, evaluations involving higher-fraction blends (approaching the 70% enrichment range) suggest that configurations exceeding this level necessitate a redesign of the injector near field to mitigate localized heat release and accelerated NO_x emissions. By identifying the operational limits for CH₄/H₂ blends in industrial settings such as steam boilers, this study offers a technical roadmap for engineering more stable, high-performance, and low-carbon energy infrastructure. Full article

Sustainable urban freight logistics requires routing decisions that jointly account for operating cost, vehicle technology, low-emission-zone (LEZ) access, terrain-sensitive energy use, and battery feasibility. This study develops a policy–terrain-coupled mixed-fleet routing framework integrating LEZ exposure, system-level carbon settlement, terrain-sensitive energy consumption, electric-vehicle (EV) battery feasibility, and route-level EV/internal-combustion-engine vehicle reassignment within a unified daily total operational cost (DTOC) evaluator. An adaptive large-neighborhood search (ALNS) procedure reconstructs feasible routes, while vehicle type is re-evaluated through counterfactual comparison of the complete system objective. The main experiments use 60 enhanced Gehring–Homberger benchmark-derived scenarios and 20 independent seeds, supplemented by ablation, carbon-price, EV-fixed-cost, heuristic-weight, convergence, and customer-scale scalability analyses. The ALNS-based framework achieves the lowest mean DTOC among the tested procedures, albeit with higher runtime. Policy and terrain information alter modeled fleet composition, with topology-dependent cost effects. Lower EV fixed costs consistently increase EV share, whereas carbon-price effects vary across network structures. All runs in the additional 200–1000-customer tests were feasible, although runtime increased with problem size. London- and Madrid-informed cases are treated as archetypes rather than as real-world validation cases. These results provide a basis for scenario screening and comparative planning of policy–terrain interactions before city-specific calibration and deployment. Full article

During the study of premixed NH₃/CH₄ fuel mixtures, flame separation into two reaction zones was observed upon flashback into a Bunsen burner. Stable combustion regimes were obtained, with a gap between the burner rim and the upper luminous region, the size of which depended on the mixture composition and the position of the combustion zone inside the burner. The work examines combustion regimes of NH₃/CH₄ mixtures with an ammonia content of 10–60% in the fuel blend. The equivalence ratio was varied in the range of 0.95–1.1. The Reynolds number was maintained in the range of 270–300, ensuring laminar flow conditions. At the burner exit, temperature and gas composition profiles were measured. Flame emission was recorded at the chemiluminescence bands of OH* (308 nm) and CH* (431 nm), and emission spectra were acquired both inside and outside the burner. Spectra in the range of 190–1080 nm were recorded. Spectral analysis revealed a band corresponding to NO₂ emission in the upper part of the luminous region. It is most likely that nitrogen dioxide is formed through low-temperature reactions occurring when the combustion products mix with atmospheric air. Full article

The transition to a low-carbon energy paradigm requires reducing nitrogen oxide NO_x and carbon monoxide CO emissions to 5–9 ppm. This study investigates the impact of the primary zone excess air ratio α and mixing quality on pollutant yields, addressing the “seesaw” trade-off mechanism between NO_x and products of incomplete combustion. Analysis of Lean Premixed and Micromix technologies demonstrates that achieving NO_x levels below 5 ppm requires local α fluctuations to remain within a root-mean-square deviation of 3–4%. An original burner design with an intelligent emission control system is presented, enabling dynamic adjustment of local αin to maintain combustion within a narrow stability window. Experimental results confirm that minimum toxicity, with NO_x concentrations below 20 ppm, is achieved at α_in = 1.7–1.8. The implementation of this technology ensures stable operation across transient and part-load regimes while mitigating thermal NO_x formation and thermoacoustic instabilities. Full article

Exposure to nitrogen oxide (NOx) in underground mining workings poses a significant threat to the health and safety of workers, while NOx emissions also represent an important environmental challenge associated with the operation of diesel-powered mining equipment. This article provides an overview of primary and secondary methods for limiting emissions and reducing exposure to NOx under underground mining conditions. The primary methods include intensified ventilation, extended ventilation time after blasting, the use of low-emission fuels, and modifications to combustion engines, including exhaust gas recirculation (EGR). The secondary methods include the use of exhaust gas purification technologies such as photocatalysis, oxidation catalysts (DOCs), selective catalytic reduction (SCR), and nitrogen oxide traps (LNTs). The presented solutions were compared in terms of NOx reduction efficiency, implementation costs, technical requirements, and practical applicability in underground workings. The most effective strategies in the short and long term were identified, taking into account the growing role of machine park electrification as a potentially sustainable solution to reducing emissions at their sources. Additionally, an SWOT analysis of NOx emission reduction methods designed for deep underground ore mines was conducted, enabling assessment of their strengths and weaknesses as well as opportunities and threats related to their implementation. The results can support the selection of NOx emission reduction methods that take into account environmental protection, worker safety, technical possibilities, and implementation costs and thus contribute to more sustainable underground mining. Full article

The global energy transition is driving power systems toward lower-carbon electricity generation, requiring sustainability assessments that consider environmental burdens beyond direct carbon emissions. This study evaluates Mexico’s electricity system using life cycle assessment, resource analysis, and energy sustainability indices. The main novelty of this study is the development of four energy sustainability indices derived from EI99H damage results: the Index of Environmental Change per Energy Unit, Relative Environmental Change Index, Per Capita Environmental Impact, and Environmental Intensity Metric. These indices capture temporal environmental change, generation-related variation, population-related burden, and environmental impact per unit of electricity. Results show improvements in fuel oil, water, and biomass performance between 2013 and 2023, whereas natural gas and coal impacts increased. Mexico exhibits a lower per capita environmental burden than Germany and Spain, while France shows the lowest value, largely due to its nuclear-based electricity mix. Human Health damage is 55% higher than Ecosystem Quality, mainly due to fossil fuel combustion. Hydroelectric generation shows substantial water demand, while solar and wind have negligible requirements. Rising natural gas costs constrain competitiveness, whereas renewables maintain low operating costs. Full article

Prescribed fire is an effective tool for reducing wildfire risk but emits pollutants such as carbon monoxide (CO) and fine particulate matter (PM_2.5) that negatively impact both indoor and outdoor air quality. While emissions from prescribed fires have been widely characterized, there remains limited understanding of how emissions vary across combustion conditions, fuel types, and regions. More specifically, there has been little work that has looked at both emissions of CO and PM_2.5 as well as other compounds such as elemental carbon (EC), organic carbon (OC), and speciated organic compounds. This work quantifies the variability of emission factors (EFs) for CO, PM_2.5, EC, OC, and speciated organic compounds across 19 prescribed fires in Colorado and southeastern Georgia using low-cost sensors. This allowed us to have highly temporally resolved EF datasets across multiple monitors and multiple burns. Results show that CO EFs are strongly driven by combustion phases, with higher emissions associated with lower modified combustion efficiency, or smoldering combustion (+3260%). However, PM_2.5 EFs exhibit weaker and more variable relationships with combustion phase and are more strongly influenced by fuel type (+108% for Colorado-based fuels) and burn characteristics (+8.3%). Broadcast burns generally exhibited higher CO and PM_2.5 EFs than pile burns, while daytime burning conditions were associated with lower emissions for both CO and PM_2.5. The results provide improved emission factor estimates across multiple conditions and can inform both prescribed fire management practices and the development of more representative emissions inventories. Full article

The environmental sustainability of passenger-car electrification depends not only on powertrain technology but also on vehicle size, material intensity, energy-system decarbonisation, and end-of-life management. This study applies prospective life cycle assessment to compare battery electric vehicles (BEVs) with gasoline-powered internal combustion engine vehicles (ICEVs) across A/B, C, and SUV segments for 2025 and 2050, including a Paris Agreement-aligned 2050 pathway. ReCiPe 2016, IPCC 2021, Cumulative Energy Demand, CML-IA, and Ecological Scarcity 2021 were applied to evaluate climate, energy, resource, ecosystem, and policy-weighted environmental pressures, while well-to-tank and tank-to-wheel modelling quantified operational emissions. Environmental burdens generally increased with vehicle segment, and BEVs showed higher production-stage impacts because of traction batteries and electric-powertrain components. Recycling reduced most indicators but increased eutrophication in some variants, demonstrating the risk of burden shifting. In the integrated manufacturing-to-wheel assessment, BEVs achieved approximately 49% lower greenhouse gas emissions than gasoline ICEVs in the A/B segments and 54–55% lower emissions in the C and SUV segments under 2025 conditions. The results show that electrification alone is insufficient to ensure sustainable mobility. Its environmental benefits are maximised when combined with vehicle right-sizing, appropriately sized batteries, low-carbon electricity, energy-efficient manufacturing, and high-quality closed-loop recycling. Full article

Flue gas recirculation (FGR) is an effective technique for reducing thermal nitrogen oxide (NO_x) emissions of gas turbines. However, variations in inlet oxygen concentration significantly alter the internal combustion characteristics of staged swirl combustors and induce combustion instability. To clarify the coupling mechanism between oxygen content and combustion stability under diverse operating conditions, three-dimensional numerical simulations are performed on a staged swirl combustor. The effects of oxygen mass fraction ranging from 11% to 23%, together with multiple operating parameters including inlet temperature, inlet velocity and operating pressure, on flame morphology, velocity fluctuation, heat release fluctuation and pressure fluctuation, are systematically investigated. The results show that increasing the inlet temperature optimises the uniformity of heat release, compensates for the combustion inhibition under low-oxygen conditions, and effectively improves combustion stability. Oxygen content exhibits a non-monotonic regulatory effect on combustion pulsation characteristics. Appropriate reduction of oxygen content narrows the high-temperature reaction zone and suppresses pressure fluctuations, thereby improving combustion stability, whereas a moderate low-oxygen condition of 17% aggravates velocity fluctuations and deteriorates combustion stability. Although elevated oxygen content enhances the overall heat release intensity, it increases the amplitude and dominant frequency of heat release fluctuations, which triggers combustion instability. Furthermore, high inlet velocity and high operating pressure amplify the disturbance of low-oxygen environments on the flame field and further degrade combustion stability. This study clarifies the competitive and coupling relationships among oxygen concentration, operating parameters and combustion dynamic characteristics, providing a theoretical basis for the stability optimisation and low-oxygen combustion regulation of gas turbine combustors with flue gas recirculation. Full article

The planning-stage estimation of fuel-related carbon emissions from construction equipment is constrained by a mismatch between the detailed operational data required for high-resolution methods and the limited information available before construction begins. This study develops a transparent, deterministic framework that converts basic project information and bill of quantities (BOQ) data into equipment workloads, operating hours, fuel consumption, and fuel-related carbon emissions. Standardized productivity values from the 2025 Standard Production Unit System for Construction Works, hourly fuel-consumption rates from the 2025 Construction Equipment Cost Estimation Table, the IPCC fuel-combustion methodology, and an ecoinvent-based upstream fuel factor are integrated through process-level conversion rules. The methodological contribution lies in operationalizing these existing data sources as a traceable low-data estimation chain rather than introducing new productivity or emission factors. In a residential-building case study, earthwork and retaining works and reinforced concrete works accounted for most of the recorded diesel consumption. The predicted fuel-consumption intensity was 10.5 L/m² compared with an actual value of 13.9 L/m², while the excavator estimate showed a substantially larger equipment-level deviation. Analytical sensitivity analysis indicates that workload and fuel-rate assumptions affect estimates proportionally, whereas productivity assumptions have an inverse effect. The framework is therefore intended as a preliminary planning and screening tool; equipment-level calibration requires higher-resolution operating-hour and refueling records. Full article