Smoke emissions due to burning of green waste in the Mediterranean area: influence of fuel moisture content and fuel mass

International audienceThe aim of this study was to investigate emission characteristics in relation to differences in fuel moisture content (FMC) and initial dry mass. For this purpose, branches and twigs with leaves of Cistus monspeliensis were burned in a Large Scale Heat Release apparatus coupled to a Fourier Transform Infrared Spectrometer. A smoke analysis was conducted and the results highlighted the presence of CO2, H2O, CO, CH4, NO, NO2, NH3, SO2, and non-methane organic compounds (NMOC). CO2, NO, and NO2 species are mainly released during flaming combustion, whereas CO, CH4, NH3, and NMOC are emitted during both flaming and smoldering combustion. The emission of these compounds during flaming combustion is due to a rich fuel to air mixture, leading to incomplete combustion. The fuel moisture content and initial dry mass influence the flame residence time, the duration of smoldering combustion, the combustion efficiency, and the emission factors. By increasing the initial dry mass, the emission factors of NO, NO2, and CO2 decrease, whereas those of CO and CH4 increase. The increase of FMC induces an increase of the emission factors of CO, CH4, NH3, NMOC, and aerosols, and a decrease of those of CO2, NO, and NO2. Increasing fuel moisture content reduces fuel consumption, duration of smoldering, and peak heat release rate, but simultaneously increases the duration of propagation within the packed bed, and the flame residence time. Increasing the initial dry mass, causes all the previous combustion parameters to increase. These findings have implications for modeling biomass burning emissions and impacts

Influence of particle size on the heat release rate and smoke opacity during the burning of dead Cistus leaves and twigs

International audienc

Smoke emissions due to burning of green waste in the Mediterranean area: influence of fuel moisture content and fuel mass

International audienceThe aim of this study was to investigate emission characteristics in relation to differences in fuel moisture content (FMC) and initial dry mass. For this purpose, branches and twigs with leaves of Cistus monspeliensis were burned in a Large Scale Heat Release apparatus coupled to a Fourier Transform Infrared Spectrometer. A smoke analysis was conducted and the results highlighted the presence of CO2, H2O, CO, CH4, NO, NO2, NH3, SO2, and non-methane organic compounds (NMOC). CO2, NO, and NO2 species are mainly released during flaming combustion, whereas CO, CH4, NH3, and NMOC are emitted during both flaming and smoldering combustion. The emission of these compounds during flaming combustion is due to a rich fuel to air mixture, leading to incomplete combustion. The fuel moisture content and initial dry mass influence the flame residence time, the duration of smoldering combustion, the combustion efficiency, and the emission factors. By increasing the initial dry mass, the emission factors of NO, NO2, and CO2 decrease, whereas those of CO and CH4 increase. The increase of FMC induces an increase of the emission factors of CO, CH4, NH3, NMOC, and aerosols, and a decrease of those of CO2, NO, and NO2. Increasing fuel moisture content reduces fuel consumption, duration of smoldering, and peak heat release rate, but simultaneously increases the duration of propagation within the packed bed, and the flame residence time. Increasing the initial dry mass, causes all the previous combustion parameters to increase. These findings have implications for modeling biomass burning emissions and impacts

Smoke emissions due to burning of green waste in the Mediterranean area: influence of fuel moisture content and fuel mass

International audienceThe aim of this study was to investigate emission characteristics in relation to differences in fuel moisture content (FMC) and initial dry mass. For this purpose, branches and twigs with leaves of Cistus monspeliensis were burned in a Large Scale Heat Release apparatus coupled to a Fourier Transform Infrared Spectrometer. A smoke analysis was conducted and the results highlighted the presence of CO2, H2O, CO, CH4, NO, NO2, NH3, SO2, and non-methane organic compounds (NMOC). CO2, NO, and NO2 species are mainly released during flaming combustion, whereas CO, CH4, NH3, and NMOC are emitted during both flaming and smoldering combustion. The emission of these compounds during flaming combustion is due to a rich fuel to air mixture, leading to incomplete combustion. The fuel moisture content and initial dry mass influence the flame residence time, the duration of smoldering combustion, the combustion efficiency, and the emission factors. By increasing the initial dry mass, the emission factors of NO, NO2, and CO2 decrease, whereas those of CO and CH4 increase. The increase of FMC induces an increase of the emission factors of CO, CH4, NH3, NMOC, and aerosols, and a decrease of those of CO2, NO, and NO2. Increasing fuel moisture content reduces fuel consumption, duration of smoldering, and peak heat release rate, but simultaneously increases the duration of propagation within the packed bed, and the flame residence time. Increasing the initial dry mass, causes all the previous combustion parameters to increase. These findings have implications for modeling biomass burning emissions and impacts

Measures of the pollutants emitted during the combustion of Cistus monspeliensis twigs according to the diameters of these particles

International audienceOur study aims to determine the particles size of plant involved in fire spread , in order to estimate the amount of leaves, twigs and wood implicated in fire spread. Thereby, it was determined from thermal parameters (HRR, mass loss, THR, efficiency) that the diameters of Cistus monspeliensis less than 4 mm, burn very quickly. These diameters are considered as elements that contribute to firespread. This first result on the particle size (< 4mm) involved in fire spread will lead to better estimate the fuel load to be taken into account in the propagation models (percentage of real burden of vegetation on the ground according to the effective size of the particles and their fraction in the plant). This fuel load is an important parameter for determining the fire propagation, the calculation of its intensity and the interpretation of its impact. Moreover, it is observed two humps of HRR from particle size above 5 mm. The second humpis increasingly important according to the growth of particles diameters. This result indicates a change in fire behavior of twigs between 4 and 5 mm. These elements largely burn behind the flame front. The second part of this study is devoted to the characterization of pollutants emitted by Cistus monspeliensis twigs burned according to their sizes. It aims to determine the quantities of pollutants potentially inhalable by the personnel involved (firefighters) and the exposed population. Further, it has been shown that CO2 is the most emitted gas with constant quantities according to the particles sizes. Other identified gases are CH4, NOx and 17 NMVOC

Multi-scale modelling of wood degradation using thermally thin wood plates

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Emission Factors for the Burning of Decking Slabs Made of Wood and Thermoplastic with a Cone Calorimeter

Smoke is an important component of wildfires. Specifying the combustion process of different materials allows scientists to better prevent and adopt public health measures. This experimental study contributes to a better characterisation of the smoke emitted by two types of decking, wood and thermoplastic, commonly used in terraces. Emission factors were characterised using a cone calorimeter for different incident fluxes ranging from 10 to 50 kW/m2. The study showed that compared to wooden (pine) decking, thermoplastic (polypropylene) decking produces more gases and aerosols, less VOCs, but with a chemical composition that is more carcinogenic

A review of thermal exposure and fire spread mechanisms in large outdoor fires and the built environment

Due to socio-economic and climatic changes around the world, large outdoor fires in the built environment have become one of the global issues that threaten billions of people. The devastating effects of them are indicative of weaknesses in existing building codes and standard testing methodologies. This is due in part to our limited understanding of large outdoor fire exposures, including the ones from wildland to communities and within communities. To address this problem, the Ignition Resistance Committee (IRC) of the International Association of the Fire Safety Science working group ‘Large Outdoor Fires and the Built Environment’ was established. This manuscript is the result of one of the IRC's initiatives to review current knowledge on exposures associated with large outdoor fires, identify existing knowledge gaps, and provide recommendations for future research. The article consists of two sections: the wildland fire exposure to the built environment and the settlement fire exposure to structures. Each section presents a comprehensive review of experimental and numerical studies of exposure mechanisms (flame contact and convection, radiation, and firebrands). The review concludes with a discussion on data consistency and existing knowledge gaps to highlight future directions for each of the three fire exposure mechanisms