Review of emissions from smouldering peat fires and their contribution to regional haze episodes

Smouldering peat fires, the largest fires on Earth in terms of fuel consumption, are reported in six continents and are responsible for regional haze episodes. Haze is the large scale accumulation of smoke at low altitudes in the atmosphere. It deteriorates air quality, disrupts transportation and causes health emergencies. Research on peat emissions and haze is modest at best and many key aspects remain poorly understood. Here, we compile an up-to-date inter-study of peat fire emission factors (EFs) in the literature both from laboratory and field studies. Tropical peat fires present larger EFs for the prominent carbon gas species than boreal and temperate peat fires, possibly due to the higher fuel carbon content (56.0% vs. 44.2%). In contrast, tropical peat fires present slightly lower PM2.5 EFs for unknown reasons but probably related to combustion dynamics. An analysis of the modified combustion efficiency, a parameter widely used for determining the combustion regime of wildfires, shows it is partially misunderstood and highly sensitive to unknown field variables. This is the first review on smouldering peat emissions and haze. Our integration of the existing literature, allows for the identification of existing gaps in knowledge and is expected to accelerate progress towards mitigation strategies

Steam exploded pine wood burning properties with particle size dependence

Power generation using waste material from the processing of agricultural crops can be a viable biomass energy source. However, there is scant data on their burning properties and this work presents measurements of the minimum explosion concentration (MEC), flame speed, deflagration index (Kst), and peak pressure for pulverised pine wood and steam exploded pine wood (SEPW). The ISO 1 m3 dust explosion vessel was used, modified to operate on relatively coarse particles, using a hemispherical dust disperser on the floor of the vessel and an external blast of 20 bar compressed air. The pulverized material was sieved into the size fractions <500 μm, <63 μm, 63–150 μm, 150–300 μm, 300–500 μm to study the coarse particles used in biomass power generation. The MEC (Ø) was measured to be leaner for finer size fraction with greater sensitivity of explosion. The measured peak Kst was 43–122 bar m/s and the maximum turbulent flame speeds ∼1.4–5.4 m/s depending on the size distribution of the fraction. These results show that the steam exploded pine biomass was more reactive than the raw pine, due to the finer particle size for the steam exploded biomass

Current Wildland Fire Patterns and Challenges in Europe : A Synthesis of National Perspectives

Changes in climate, land use, and land management impact the occurrence and severity of wildland fires in many parts of the world. This is particularly evident in Europe, where ongoing changes in land use have strongly modified fire patterns over the last decades. Although satellite data by the European Forest Fire Information System provide large-scale wildland fire statistics across European countries, there is still a crucial need to collect and summarize in-depth local analysis and understanding of the wildland fire condition and associated challenges across Europe. This article aims to provide a general overview of the current wildland fire patterns and challenges as perceived by national representatives, supplemented by national fire statistics (2009-2018) across Europe. For each of the 31 countries included, we present a perspective authored by scientists or practitioners from each respective country, representing a wide range of disciplines and cultural backgrounds. The authors were selected from members of the COST Action "Fire and the Earth System: Science & Society" funded by the European Commission with the aim to share knowledge and improve communication about wildland fire. Where relevant, a brief overview of key studies, particular wildland fire challenges a country is facing, and an overview of notable recent fire events are also presented. Key perceived challenges included (1) the lack of consistent and detailed records for wildland fire events, within and across countries, (2) an increase in wildland fires that pose a risk to properties and human life due to high population densities and sprawl into forested regions, and (3) the view that, irrespective of changes in management, climate change is likely to increase the frequency and impact of wildland fires in the coming decades. Addressing challenge (1) will not only be valuable in advancing national and pan-European wildland fire management strategies, but also in evaluating perceptions (2) and (3) against more robust quantitative evidence.Peer reviewe

Review of emissions from smouldering peat fires and their contribution to regional haze episodes

Smouldering peat fires, the largest fires on Earth in terms of fuel consumption, are reported in six continents and are responsible for regional haze episodes. Haze is the large-scale accumulation of smoke at low altitudes in the atmosphere. It decreases air quality, disrupts transportation and causes health emergencies. Research on peat emissions and haze is modest at best and many key aspects remain poorly understood. Here, we compile an up-to-date inter-study of peat fire emission factors (EFs) found in the literature both from laboratory and from field studies. Tropical peat fires yield larger EFs for the prominent organic compounds than boreal and temperate peat fires, possibly due to the higher fuel carbon content (56.0 vs 44.2%). In contrast, tropical peat fires present slightly lower EFs for particulate matter with diameter ≤2.5 μm (PM2.5) for unknown reasons but are probably related to combustion dynamics. An analysis of the modified combustion efficiency, a parameter widely used for determining the combustion regime of wildfires, shows it is partially misunderstood and highly sensitive to unknown field variables. This is the first review of the literature on smouldering peat emissions. Our integration of the existing literature allows the identification of existing gaps in knowledge and is expected to accelerate progress towards mitigation strategies

Inertization of ignition in biomass dust layers

The use of biomass has heavily increased in the past years, and so has the number of accidents related to its storage, transport, and use.In this context, it is important to define the flammability and explosion characteristics in order to have a proper knowledge of materialsbehaviour and prevent accidents (Eckhoff 2003). The present work aims to study ignition inertization in biomass dust layers. To do so, woodpellets were milled and sieved obtaining a < 1 mm particle size sample. The samples flammability characteristics were defined troughminimum ignition temperature of dust layer and cloud (MIT-l and MIT-c) and minimum ignition energy (MIE). Moreover, the characterizationwas completed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) so moisture, volatile content, maximum weight loss temperature, etc., were defined.Furthermore, the present study focuses on a possible solution to biomass flammability tendency by adding solid inert material (Danzi,Marmo, and Riccio 2015; Janés and Carson 2013). In particular, two different inert materials were used (sodium bicarbonate and recycledglass) and mixed with biomass at different concentrations (30%, 50% and 70%). Once the mixed samples were produced, minimum ignitiontemperature of layer (MIT-l) was defined for each sample, so the inerting effect was clearly noticed. Additionally, the samples (both raw andmixed with inerts) were tested using TGA and DSC techniques in order to analyze their thermal behaviour, thus allowing the definition of athreshold that indicates the optimal inert concentration that significantly increases MIT-l while the heating value is not substantially reduced

Reviewing Particle Size Influence in Biomass flammability and Explosibility

Due to the new policies implemented to mitigate and reduce climate change effects, the use of biomass has significantly increased in thelast years, and so, the number of accidents related to biomass storage, use, transport, and handle. Several authors have focused theirresearch on biomass flammability and explosion severity properties, together with the influence of chemical and physical characteristics,finding out that particle size (PS) presents a major effect on those properties (Eckhoff, 2009; Guo et al., 2012). In order to increase biomasssafety knowledge, PS has been widely studied, however, most of the published research determines PS using common methods that donot properly define this parameter. As biomass presents elongated and fibrous shape, granulometry methods that approach particles tospheres do not properly characterize biomass particles, which leads to misunderstandings when assessing relationship between granulometryand flammability properties (Gil et al., 2014). The aim of this study is to collect published information regarding biomass granulometry andflammability so assessment can be carried out. Indeed, it was found out that most of the published research determines PS using laserdiffraction whose error when testing fibrous particles is quite significant. The obtained results were compared to coal samples, as their characteristics are further studied. From data, it was noticed that biomass samples present a wide particle size range and, even whenconsidering biomass with similar particle size distributions, important deviations were found when assessing flammability and explosibilityproperties. Furthermore, it was clear that there is no standard method for particle size determination which can unify results in order tocarry out comparisons between samples. Moreover, the public existing data regarding biomass industrial safety is not extensive and shouldbe increased to help understand biomass behavior

Behaviour of smoldering fires during periodic refilling of wood pellets into silos

The evolution of smoldering fires in biomass stored in lab-scale silos with additional fuel material supplied repeatedly, has been studied. The direct effects of the added material on the sample are: cooling, enhanced thermal insulation, and facilitation of more intense combustion at a later stage. This article focuses on the cooling, which leads to an almost instantaneous reduction in the combustion rate. Surprisingly, this reduction does not vary only with the amount of material refilled – but also depends strongly on the stage of the smoldering process. This demonstrates that the underlying smoldering processes merely to a certain degree are regularized by the periodic refillings. Quantitatively, the functional relationship between the refilled amount and the change in combustion rate caused by the refilling was determined. The results displays four regimes, that reflect different stages of the smoldering process at the time of the refilling. Using the Arrhenius equation, we find for one of these regimes an expression for the ratio of combustion rates (immediately after to immediately before the refill) as function of the amount of added material. This expression contains only one free (undetermined) parameter. We determine the value of this parameter from the data and demonstrate that this value is consistent with a simple model for how the sudden cooling occurs spatially in the sample