Search Results (304)

Bioaerosols released during wildland and prescribed fires may influence ecosystems, air quality, and microbial dispersal, yet their transport and deposition remain poorly understood. This study combined infrared uncrewed aircraft system (UAS) observations of a prescribed burn with the coupled fire–atmosphere model WRF-SFIRE and a Lagrangian particle model in order to evaluate how uncertainties in simulated fire behavior affect predicted bioaerosol (bacterial cell) transport and deposition. A reconstruction of the observed spatiotemporal evolution of the fire was derived from thermal UAS measurements acquired during the burn and incorporated into a WRF-SFIRE simulation, in which the modeled fire spread was constrained to follow this reconstructed progression. This benchmark run was compared with two unconstrained, fully coupled simulations that used a low and a high estimate of fuel moisture content (FMC) to represent typical uncertainty in fire rate of spread (ROS) prediction. Despite substantial differences in fire intensity and plume dynamics among the simulations, the resulting bioaerosol transport pathways and deposition patterns were broadly consistent across cases. The horizontal transport of the bioaerosols was dominated by the ambient Easterly wind and the bioaerosols were lofted by fire-affected updrafts—some exceeding 10 m/s—within the buoyant plume structure resolved in WRF-SFIRE. Deposition hot-spots appeared in consistent locations in the three simulations, especially regions where topography forced up-slope transport. Although the most intense fire produced slightly greater local deposition—likely due to a combination of stronger fire-induced downdrafts and overturning from penetration into strong vertical wind shear above the boundary layer—differences were small relative to the overall deposition footprint. These results suggested that, for burns of this scale, bioaerosol transport and deposition predictions are relatively robust to realistic uncertainties in fire-behavior modeling. This finding indicates that coupled fire–atmosphere and particle-transport modeling frameworks could be employed to quantitatively forecast microbial transport and deposition during future controlled burn experiments. Full article

Brazil is the main coffee producer in the world. However, the impacts of climate change driven by greenhouse gas (GHG) emissions pose a major challenge for agriculture in tropical regions. This study established a GHG inventory of coffee production on farms in southern Minas Gerais, Brazil, over a two-year period, adopting a cradle-to-farm-gate approach. It considered scopes 1 and 2 emissions from on-farm activities. The emission inventories were based on Intergovernmental Panel on Climate Change (IPCC) methodologies adapted for Brazilian conditions. The emissions were categorized in direct and biogenic and by area (in hectares) and production (kg of coffee). Electricity consumption, fossil fuel use, wood burning and fertilizer application were considered. Direct total emissions ranged from 2617 to 6211 t CO₂e, 2.67 to 3.81 t CO₂e ha⁻¹, and from 1.52 to 4.59 kg CO₂e kg⁻¹ of coffee. Biogenic emissions ranged from 336 to 4955 t CO₂e, 0.28 to 2.95 t CO₂e ha⁻¹, and from 0.32 to 2.21 kg CO₂e kg⁻¹ of coffee. Urea-based nitrogen fertilizers were the main source of direct emission and wood burning was the main source of biogenic emission. Management practices such as applying non-urea-based fertilizers, adjusting nitrogen rates according to soil analyses and manual harvesting contributed to mitigating GHG emissions. The observed emission intensities were consistent with other reported values for Brazilian coffee production. Further reductions may be achieved by adopting agroforestry systems, increasing coffee straw retention in the soil and replacing urea with alternative nitrogen sources, including slow-release fertilizers and urease-inhibitor technologies. Full article

Prescribed burning is important for reducing wildfire risk and regulating fuel loads, but its implementation in mountainous forests is strongly influenced by the coupled effects of the wind field and topography, making it difficult to control. This study focuses on Yunnan pine (Pinus yunnanensis) forests in southwestern China. A three-dimensional Fire Dynamics Simulator (FDS) combined with measured fuel characteristics was used to simulate 21 slope (0–35°) and wind speed (0–2 m s⁻¹) combinations to quantitatively analyze the fire spread, flame structure, and gaseous emission characteristics during downslope prescribed burning. The local fire spread rate (ROS), evaluated along three lateral lines (Y = 2.5, 5.0, and 7.5 m), exhibits a non-monotonic dependence on slope over the tested range, with a minimum near 30° and a modest rebound at 35°. A downslope wind of 1 m s⁻¹ promotes near-surface heating and accelerates spread, whereas a stronger wind of 2 m s⁻¹ lifts flames away from the fuel bed and suppresses combustion. Thermal field analysis reveals that peak temperature decreases with increasing slope and that a late-stage secondary heating episode occurs at 35°. CO₂ emissions are significantly positively correlated with fuel consumption, reaching a peak of 717.5 kg under a 35° slope and no-wind conditions. CO emissions, as an indicator of combustion efficiency, reach their highest value of 2.23 kg at a 35° slope and a wind speed of 1 m s⁻¹, indicating that their trend is not entirely consistent with the ROS and temperature and that there is a certain degree of decoupling. The interaction between slope and wind speed transforms fire behavior from a cooperative to a competitive mechanism, and the topography–wind field coupling provides differentiated control over the combustion intensity and completeness. This study provides a scientific basis for the safe implementation of mountain burning programs and for regional carbon emission assessments. Full article

Combining biobutanol and oxyhydrogen in an SI engine can reduce fossil-fuel use and improve power, but oxyhydrogen increases NOx. Without sacrificing combustion stability, this work investigates lean–burn coupled with exhaust gas recirculation for a gasoline port injection + biobutanol direct injection + oxyhydrogen in-cylinder negative pressure indraft engine, across five oxyhydrogen flow levels, four exhaust gas recirculation ratios, and three excess air ratios. Results show that with lean–burn + exhaust gas recirculation, oxyhydrogen more effectively lowers the coefficient of variation of indicated mean effective pressure and increases indicated mean effective pressure, peak cylinder pressure, and peak heat release rate. With 16 L/min oxyhydrogen, the negative effects of 6–12% exhaust gas recirculation on CA 0–10 and CA 10–90 are mitigated for all excess air ratios, and the crank angle corresponding to peak pressure remains optimal under lean conditions when 6% ≤ exhaust gas recirculation ≤ 12%. Oxyhydrogen reduces CO and HC after exhaust gas recirculation, while lean–burn dominates CO reduction. Exhaust gas recirculation suppresses NO more than lean–burn. At 1.1 ≤ excess air ratios ≤ 1.2, the optimal exhaust gas recirculation is 12%, ensuring favorable in-cylinder conditions. Overall, lean–burn + exhaust gas recirculation effectively controls NO and maximizes thermal efficiency and renewable-fuel substitution. The optimal strategy is “oxyhydrogen = 16 L/min, exhaust gas recirculation = 12%, 1.1 ≤ excess air ratios ≤ 1.2”. Full article

Cellular automata-based wildfire simulation models are widely used to support fire management, risk assessment, and operational decision-making, due to their efficiency and computational advantages. However, the accuracy of these models heavily depends on the quality of input data provided by the user, including the composition and geospatial extend of forest fuels, current meteorological conditions and terrain information. This publication examines how quantitative and spatial input data uncertainties affect the estimates of the impacted areas. Using a series of simulation experiments, inaccurate data are introduced to specific input variables (such as the vegetation type and the fuel moisture content) to reflect realistic levels of uncertainty commonly observed in operational scenarios, where users with different cognitive backgrounds fail to properly identify key characteristics of a fire. Model outputs are then compared using spatial and temporal performance metrics, including the rate of spread and burned area extent. The results demonstrate that uncertainties in fuel models and meteorological inputs exert a dominant influence on simulated fire behavior. Our findings highlight the sensitivity of wildfire simulations to compounded input uncertainties and stress the need for improved in-field data acquisition strategies. Full article

Wildland fires, including surface and crown fires, present significant challenges for ecosystems and forest management. Accurate fire modelling is crucial for risk assessment and mitigation strategies. The Fire Dynamics Simulator (FDS) v6.8.0, developed by the National Institute of Standards and Technology (NIST), is a physics-based model that simulates fire behaviour by incorporating advanced physics and chemistry. However, its reliability requires thorough validation. This study validates FDS 6.8.0’s performance in modelling both surface fires and single tree burning. Two separate simulation sets were conducted. For surface fires, pine needle fuel beds were used at a laboratory scale to examine fire behaviour on slopes of 0°, 10°, and 20°. The results were validated against experimental data. A burning Douglas fir tree was simulated, and the results were compared with experimental measurements. The surface fire simulations at 0° and 10° slopes showed strong agreement with experimental data. In single-tree burning, both experimental and simulated results exhibited similar trends, with a rapid increase to a peak mass-loss rate (MLR) followed by a gradual decline. Validating FDS 6.8.0 forms an essential first step toward supporting the investigation of complex wildland fire behaviour, such as surface-to-crown fire transition, canyon fire, and dynamic escalation, using the same FDS version. Full article

Combustion duration is a fire behaviour feature relevant for both the effects and management of fire. We burned small-scale laboratory fuel beds (n = 135) of eight fuel types and developed empirical models to describe variation in flame residence and burn-out times, and fuel mass fraction loss rates during flaming and non-flaming combustion; each fuel sample was ignited at once and burned as a pile. Surface area-to-mass ratio of the fuel particles, by itself, allowed accurate prediction of all combustion properties with better performance than surface area-to-volume ratio. Fuel bed structure was also shown to have an influence, fuel load being the variable that further improved all predictions. This work provides evidence that surface area-to-mass ratio is an adequate descriptor of the combustion characteristics of forest fuel beds. Our expectation is that this approach will assist future modelling efforts to obtain simple empirical models to predict the combustion features of free-spreading fires in a wide range of vegetation types. Full article

Twin wildfires burned over 9500 ha in Seferihisar, İzmir, western Türkiye, on 29—30 June 2025 under extreme fire weather conditions. This study reconstructs the spatiotemporal progression of the fires and examines the drivers of contrasting behaviors and burn severity. Multi-source datasets—Sentinel-2 imagery, VIIRS/MODIS thermal detections, MTG images and thermal detections, aerial photos, and ground data—were integrated to delineate progression polygons and compute rate of spread (ROS), fuel consumption (FC), and fire-line intensity (FI). Kuyucak fire showed rapid early growth, burning 3554 ha in 2.5 h (mean ROS of 5.0 km h⁻¹; mean FI of 37,789 kW m⁻¹), driven by strong northeasterly winds of 40–50 km h⁻¹, steep terrain, dense Pinus brutia fuels, and very low dead fine-fuel moisture (<6%). Kavakdere fire advanced more slowly (mean ROS of 1.6 km h⁻¹) across open grassland and cropland, yielding lower FC and FI. Synoptic analysis revealed a strong pressure-gradient-induced northeasterly wind regime linked to a mid-tropospheric geopotential height dipole between Central Europe and the Eastern Mediterranean, while WRF simulations indicated a dry boundary layer and enhanced low-level winds during peak spread. Sentinel-2 dNBR burn severity mapping showed substantial spatial variability tied to fuel and topography contrasts. Findings demonstrate how twin ignitions under similar weather conditions can produce divergent outcomes, underscoring the need for terrain- and fuel-aware strategies during extreme Mediterranean fire outbreaks. Full article

Colombia generates large volumes of lignocellulosic residues from agriculture, forestry, and agro-industrial activities. Much of this material is landfilled, openly burned, or left to decompose. These practices drive greenhouse-gas emissions (methane and CO₂), particulate air pollution, water contamination, and pest proliferation. Therefore, this study focuses on the design, simulation, exergetic and economic analysis of lignocellulosic biorefinery schemes in Colombia using corn stover (CS) as feedstock. This approach thus turns an environmental liability into valuable resources. Mass and energy balances obtained from Aspen Plus V10^® were used to calculate exergy efficiency. Economic indicators were provided by the Aspen Process Economic Analyzer (APEA) V10^® software. The first scenario (SCE01) included xylitol, lignin, carbon dioxide, biogas, and biofertilizer production along with in situ ethanol co-production; for scenario 2 (SCE02), a cogeneration (CHP) stage using biogas and biofertilizer as fuel was added; in scenario 3 (SCE03), the ethanol production of scenarios 1 and 2 was replaced by glutamic acid production. The exergy efficiency results were as follows: SCE01 (60.1%), SCE02 (36.8%), SCE03 (37.5%). The largest exergy losses were found in the CHP system. In terms of economic viability, all scenarios showed favorable economic parameters. SCE03 showed better results with an Internal Rate of Return (IRR) of 28.01% and a Net Present Value (NPV) of USD 985.1 M compared to SCE01 (27.48%; USD 769.1 M) and SCE02 (27.13%; USD 643.1 M). In light of these results, the SCE03 approach represents the most attractive investment opportunity, with the potential to integrate the social and environmental pillars of sustainability by fostering rural economic development and CO₂ capture. Optimization strategies can be readily adopted to enhance the overall efficiency of the proposed model, enabling it to serve as a benchmark for scaling and comparing alternative lignocellulosic waste valorization pathways at a national level. Full article

The characteristics of litter combustion have a significant impact on the spread of surface fires in the central Yunnan Province, a high-risk forest fire zone. The burning behavior of individual and mixed-species litter samples from five dominant tree species (Pinus yunnanensis Franch., Keteleeria evelyniana Mast., Quercus variabilis Blume., Quercus aliena var. acutiserrata, and Alnus nepalensis D. Don.) was assessed in this study using cone calorimeter tests. Fern fronds and fine branches were included in additional tests to evaluate their effects on specific combustion parameters, such as Fire Performance Index (FPI), Flame Duration (FD), Time to Ignition (TTI), Mass Loss Rate (MLR), Residual Mass Fraction (RMF), Peak Heat Release Rate (PHRR), and Total Heat Release (THR). There were remarkable differences in the burning properties of the three types of litter (broadleaf, pine needles, and short pine needles). The THR and PHRR values of P. yunnanensis were the highest, whereas the PHRR of the other species varied very little. Short pine needle litter showed incomplete combustion and a long flame duration. When measured against pure pine needle litter, mixtures of P. yunnanensis and broadleaf litter showed lower PHRR. When set side by side to pure pine needle litter, P. yunnanensis and broadleaf litter showed lower PHRR. THR rose when fine branches were included, underlining the significance of fine woody fuels in fire behavior. The insertion of ferns increases the percentage of unburned biomass, prolongs TTI, and dramatically reduces PHRR. Full article

In the steel industry, reheating furnaces are a significant source of carbon emissions. Co-firing natural gas and ammonia in reheating furnaces reduces carbon emissions and mitigates ignition difficulties and the limited flammability range of ammonia. This research develops a three-dimensional model for combustion, fluid dynamics, and heat transfer in a reheating furnace to investigate slab heating and emission with a natural gas/ammonia blended fuel. Numerical results demonstrate that, under constant calorific value conditions, the average temperature of the discharged slab decreases following ammonia blending, with the greatest temperature differential of 110 K achieved at a 10% ammonia blending ratio. Moreover, as the ammonia blending ratio increases from 0 to 40%, the mass fraction of CO first rises and subsequently declines, ultimately decreasing by 18%. Meanwhile, the CO₂ emissions at the outlet decrease by 17.6% to 40.7%. The mass fraction of unburned NH₃ rises to 0.0271, whilst NO_x emissions diminish from 49.47 ppm to 14.23 ppm. These changes are attributed to the low combustion efficiency and burning rate of ammonia, coupled with the reduced furnace temperature during ammonia-blended combustion, which weakens radiative heat transfer. Thus, optimizing the equivalence ratio along with applying hydrogen can improve the thermal efficiency of the reheating furnace. This study provides insight into the operational characteristics of a full-scale walking-beam reheating furnace operating under natural gas-ammonia co-firing conditions, providing theoretical guidance for enhancing the thermal efficiency of furnaces. Full article

The present paper discusses differences in the theoretical behavior of nonconventional biomasses during combustion according to their combustion parameters, focusing on their potential for sustainable energy valorization and their contribution to sustainable development. Data were obtained through thermogravimetric analysis (TGA) of biomasses from the local Galicia–North Portugal Euroregion. The samples tested were raw, nonwoody biomasses, specifically kiwi waste and gorse, and animal-derived biomasses, poultry and turkey manure. A wood pellet was also included as a reference conventional biofuel. Nonwoody biomass samples containing kaolin and calcium carbonate were also tested. Thermogravimetric analyses were performed on each biofuel under an oxidative atmosphere at different heating rates. With these data, different combustion parameters were calculated. The TGA results showed that the mean ignition temperature observed for animal-derived fuels was about 15 °C lower than for nonwoody biomasses at every heating rate, which indicates that they start to burn at lower temperatures. These animal-derived fuels generally presented better combustion parameters, suggesting that their combustion behavior is better; however, their high ash and moisture contents are problematic. These issues would be aggravated in real facilities, making them more difficult to use as fuel. The proportion of additives used had no effect on the parameters at lower heating rates, although they started to modify their tendency at 30 °C/min. For instance, the ignition index for non-additivated kiwi waste was 174.32 (wt. %/min³) × 10⁻³ compared to 143.78 (wt. %/min³) × 10⁻³ for kiwi with CaCO₃. Full article

As a zero-carbon fuel, ammonia holds significant potential for achieving the “dual carbon” strategic goals. However, its extremely low laminar burning velocity (LBV) limits its direct application in combustion systems. This work systematically reviews the research progress on the LBV of ammonia flames, focusing on three key aspects: measurement methods, effects of combustion conditions, and reaction kinetic models. In terms of measurement methods, the principles, applicability, and limitations of the spherical outwardly propagating flame method, Bunsen-burner method, counter-flow flame method, and heat flux method are discussed in detail. It is pointed out that the heat flux method and counter-flow flame method are more suitable for the accurate measurement of ammonia flame LBV due to their low stretch rate and high stability. Regarding the effects of combustion conditions, the LBV characteristics of pure ammonia flames under ambient temperature and pressure are summarized. The influence patterns of three factors on LBV are analyzed systematically: blending high-reactivity fuels (e.g., hydrogen and methane), oxygen-enriched conditions, and variations in temperature and pressure. This analysis reveals effective approaches to improve ammonia combustion performance. Furthermore, the promoting effect of high-reactivity fuel blending on liquid ammonia combustion was also summarized. For reaction kinetic models, various chemical reaction mechanisms applicable to pure ammonia and ammonia-blended fuels (ammonia/hydrogen, ammonia/methane, etc.) are sorted out. The performance and discrepancies of each model in predicting LBV are evaluated. It is noted that current models still have significant uncertainties under specific conditions, such as high pressure and moderate blending ratios. This review aims to provide theoretical references and data support for the fundamental research and engineering application of ammonia combustion, promoting the development and application of ammonia as a clean fuel. Full article

Wildfire-induced disturbances to soil and vegetation can significantly impact streamflows for years, depending upon the degree of burn severity. Accurately predicting the effects of wildfire on streamflow at the watershed scale is essential for effective water budget management. This study presents a novel approach to generating a burn severity map on a small scale by integrating unmanned aerial vehicle (UAV)-based thermal imagery with Landsat-derived Differenced Normalized Burn Ratio (dNBR) and upscaling burned severity to the entire burned area. The approach was applied to the Thompson Ridge Fire perimeter, and the upscaled UAV-Landsat-based burn severity map achieved an overall accuracy of ~73% and a kappa coefficient of ~0.62 when compared with the Burned Area Emergency Response’s (BAER) fire product as a reference map, indicating moderate accuracy. We then tested the transferability of burn severity information to a Beaver River watershed by applying Random Forest models. Predictors included topography, spectral bands, vegetation indices, fuel, land cover, fire information, and soil properties. We calibrated and validated the Distributed Hydrology Soil Vegetation Model (DHSVM) against observed streamflow and Snow Water Equivalent (SWE) data within the Beaver River watershed and measured model performance using Nash–Sutcliffe Efficiency (NSE), Kling–Gupta Efficiency (KGE), and Percent Bias (PBIAS) metrics. We adjusted soil (maximum infiltration rate) and vegetation (fractional vegetation cover, snow interception efficiency, and leaf area index) parameters for the post-fire model setup and simulated streamflow for the post-fire years without vegetation regrowth. Streamflow simulations using the upscaled and transferred UAV-Landsat burn severity map and the Burned Area Emergency Response’s (BAER) fire product produced similar post-fire hydrologic responses, with annual average flows increasing under both approaches and the UAV-Landsat-based simulation yielding slightly lower values, by less than 6% compared to the BAER-based simulation. Our results demonstrate that the UAV-satellite integration method offers a cost- and time-effective method for generating a burn severity map, and when combined with the transferability method and hydrologic modeling, it provides a practical framework for predicting post-fire streamflow in both burned and unburned watersheds. Full article

Ammonia (NH₃) is a promising zero-carbon fuel to eliminate carbon footprint while the high autoignition temperature and low combustion rate of NH₃ remain challenging for practical implementation. Using dimethyl ether (DME) as pilot ignition fuel can substantially promote the reactivity of NH₃, thus paving the way for a widespread application of NH₃. In this study, the ignition process and nitrogen oxides (NO_x) emissions of the NH₃ liquid spray ignited by liquid DME spray were numerically investigated using Converge software. The ambient temperatures (T_amb) ranging from 900 K to 1100 K were used to mimic the in-cylinder temperature typically encountered in turbocharger engines. The effect of ammonia energy ratio (AER) and fuel injection timing was examined as well. It is found that only half of NH₃ is consumed at T_amb = 900 K while 97.4% of NH₃ is burned at T_amb = 1100 K. Nitric oxide (NO) and nitrogen dioxide (NO₂) formation also have strong correlation with T_amb and NO₂ is usually formed around the periphery of NO through these two channels HO₂ + NO = NO₂ + OH and NO + O(+M) = NO₂(+M). Extremely high nitrous oxide (N₂O, formed by NH + NO = H + N₂O) and carbon monoxide (CO) are produced with the presence of abundant unburned NH₃ at T_amb = 900 K. Additionally, increasing AER from 60% to 90% results in slightly declined combustion efficiency of NH₃ from 98.7% to 94%. NO emission has a non-monotonical relationship with AER owing to the ‘trade-off’ relationship between HNO concentration and radical pool at varying AERs. A higher AER of 95% leads to failed ignition of NH₃. Advancing DME injection not only increases combustion efficiency, but also reduces NO_x and CO emissions. Full article