Combustion Of Litter Research Articles

Impacts of Forest Fires on Soil: Exploring the Effects on Biotic and Abiotic Components

Forest fires are a widespread occurrence in ecosystems worldwide, impacting both vegetation and soil. The effects of forest fires, as well as prescribed fires, on forest soil are complex, influencing soil organic matter, macro and micro-nutrients, and physical properties such as texture, color, pH, and bulk density, along with soil biota. The magnitude of the impact on forest soil depends on factors such as fire intensity, fuel load, and soil moisture. The severity and frequency of fire determine whether it is beneficial or harmful to the soil. Low-intensity fires can enhance plant available nutrients through the combustion of litter and soil organic matter, promoting rapid growth of herbaceous plants and increased nutrient storage. Conversely, high intensity fires can lead to complete loss of soil organic matter, volatilization of vital elements (N, P, S, K), and microbial death. Additionally, intense forest fires generate hydrophobic organic compounds that result in water-repellent soils. Forest fires also have long-term effects on forest soil. This paper aims to review the impacts of forest fires on various soil properties crucial for maintaining a healthy ecosystem.

Leaf litter combustion properties of Central European tree species

AbstractTemperate forests of Central Europe are exposed to increasing fire risk. However, little is known about combustion properties of leaf litter, which plays an important role in the spread of surface fires. We used cone calorimetry to compare combustion properties of leaf litter samples from seven common tree species of Central European forests by reconstructing a litter layer of original depth in sample holders with a size of 10 cm × 10 cm. In addition to mono-specific leaf litter beds, combustion experiments included mixtures of different litter types, mixtures of litter and bryophytes and one mixture of litter and fine woody debris, totalling to 13 different setups (i.e. litter types). Recorded combustion properties included ignitability, flaming duration and heat release. Differences in combustion properties were analysed using analyses of variance followed by pairwise post-hoc tests. Combustion properties mainly differed between different litter types (broadleaf, pine needle, short needle). Highest total and peak heat release were observed for Scots pine (Pinus sylvestris), while peak heat release rates showed only minor differences for litter of the remaining species. Broadleaf litter was characterized by highest ignitability. For short-needle litter, we observed long flaming duration and incomplete combustion, resulting in the lowest total heat release on a sample mass basis. For litter mixtures of pine and broadleaf litter, we observed lower peak heat release rates in comparison to mono-specific pine litter. Mosses reduced peak heat release rates and increased the proportion of unburned biomass. However, the magnitude of this effect differed between bryophyte species included in the mixtures. The addition of fine woody debris strongly increased total heat release, highlighting the importance of fine woody fuels for fire behaviour. The results of this study provide valuable baseline information on combustion behaviour of leaf litter from Central European forests. Due to the limitations of laboratory combustion experiments to reproduce conditions of real forest fires, there is a need for future field studies investigating fire behaviour under natural conditions.

Fluidized bed combustion of poultry litter at farm-scale: Environmental impacts using a life cycle approach

Combustion can concentrate phosphorus (P) from poultry litter into an ash product that is easier to transport for land application. This was the first life cycle assessment (LCA) study to investigate the efficacy and sustainability of a fluidized bed combustion (FBC) system using poultry litter to heat poultry houses and produce electricity, in the United States, to replace liquid propane gas (LPG) and natural gas (NG) use. The ‘Baseline scenario’ used results from a 16-month FBC monitoring study, and an ‘Improved scenario’ based on an increased biomass feed rate (0.246 tons/h), increased run-time (6720 h/y), and net positive electricity production. In the Baseline scenario, climate change potential was 32% and 44% lower than use of LPG and NG, respectively, for poultry house heating, but the low electricity production from the FBC system resulted in net electricity import and lower sustainability compared to LPG use in 12 of the 18 impact categories. The Improved scenario had 48–98% less environmental impacts than the Baseline scenario in the 18 categories. The sensitivity analysis showed that a 10% change in the electricity input for FBC operation resulted in the highest average change (4.8%) in the 18 impact categories, indicating the necessity of a net positive electrical energy output from the FBC unit for increased sustainability. The results also highlighted the impact of the replacement heating fuel type, as replacing NG through poultry litter combustion had a greater impact than replacement of LPG.

Incorporating Poultry Litter Ash as a Pre-plant Fertilizer to Reduce Nutrient Leaching during Bermudagrass Establishment

ABSTRACTPre-plant fertilizers are used to adjust soil fertility for nutrients such as phosphorus (P) during turfgrass establishment. However, nutrient applications of water-soluble sources in coarse-textured soils are prone to leaching compared to slow-release sources. Poultry litter ash (PLA), a by-product of poultry litter combustion, concentrates macronutrients into less water-soluble forms. The objective of this study was to evaluate PLA with triple superphosphate (TSP), in ratios of P in PLA to that in TSP of 0:100, 25:75, 50:50, 75:25; 100:0 as a pre-plant fertilizer incorporated into a 90:10 (v/v) sand and peat mixture seeded with bermudagrass (Cynodon dactylon L.) ‘Sahara’. Bermudagrass groundcover, shoot, and root biomass were measured at 6 weeks. Leachate was captured weekly and analyzed for P, K, Ca, and Mg. Bermudagrass groundcover and biomass accumulation were similar across all treatments at 6 weeks after planting (WAP). The benefit of PLA compared to TSP was the reduction in P, K, Ca, and Mg leached during the first two WAP. As the percentage of PLA increased relative to TSP, nutrient leaching decreased, with 100% PLA resulting in the lowest cumulative nutrient masses leached. Application of 100% PLA as a pre-plant fertilizer can limit nutrient leaching in coarse-textured media compared to more water-soluble nutrient sources, particularly TSP, without delaying bermudagrass establishment.

Front velocity in the combustion of blends of poultry litter with straw

The paper presents experimental studies on the burning characteristics of poultry litter and its blends with straw in the context of their potential usage in small-scale heat and power generation. For comparison purposes classic fuel such as wooden pellets was also investigated. The samples were analyzed in terms of water content, chemical composition and devolatilization, heating values, ash composition and ignition temperatures. An experimental analysis was performed of the combustion process of various sample beds in a small laboratory reactor that covered the temperature measurements and visual observations. This resulted in estimation of the speeds of ignition front propagation in the studied fixed beds, which is of general importance in the design of grate-fired furnaces. The combustion dynamics was discussed in terms of the physical properties of the bed, such as bulk density and porosity. The authors concluded that the main issue regarding the efficiency of poultry litter combustion was closely connected to a low bulk density of the fuel bed, which led to faster combustion front propagation but lower temperatures compared to a more dense fuel bed such as a wood pellet bed.

Moisture content prediction in poultry litter using artificial intelligence techniques and Monte Carlo simulation to determine the economic yield from energy use

The objective of this study is to determine the economic return of poultry litter combustion in boilers to produce bioenergy (thermal and electrical), as this biomass has a high-energy potential due to its component elements, using fuzzy logic to predict moisture and identify the high-impact variables. This is carried out using a proposed 7-stage methodology, which includes a statistical analysis of agricultural systems and practices to identify activities contributing to moisture in poultry litter (for example, broiler chicken management, number of air extractors, and avian population density), and thereby reduce moisture to increase the yield of the combustion process. Estimates of poultry litter production and heating value are made based on 4 different moisture content percentages (scenarios of 25%, 30%, 35%, and 40%), and then a risk analysis is proposed using the Monte Carlo simulation to select the best investment alternative and to estimate the environmental impact for greenhouse gas mitigation. The results show that dry poultry litter (25%) is slightly better for combustion, generating 3.20% more energy. Reducing moisture from 40% to 25% involves considerable economic investment due to the purchase of equipment to reduce moisture; thus, when calculating financial indicators, the 40% scenario is the most attractive, as it is the current scenario. Thus, this methodology proposes a technology approach based on the use of advanced tools to predict moisture and representation of the system (Monte Carlo simulation), where the variability and uncertainty of the system are accurately represented. Therefore, this methodology is considered generic for any bioenergy generation system and not just for the poultry sector, whether it uses combustion or another type of technology.

Mercury distribution in two Sierran forest and one desert sagebrush steppe ecosystems and the effects of fire

Mercury (Hg) concentration, reservoir mass, and Hg reservoir size were determined for vegetation components, litter, and mineral soil for two Sierran forest sites and one desert sagebrush steppe site. Mercury was found to be held primarily in the mineral soil (maximum depth of 60 to 100 cm), which contained more than 90% of the total ecosystem reservoir. However, Hg in foliage, bark, and litter plays a more dominant role in Hg cycling than the mineral soil. Mercury partitioning into ecosystem components at the Sierran forest sites was similar to that observed for other US forest sites. Vegetation and litter Hg reservoirs were significantly smaller in the sagebrush steppe system because of lower biomass. Data collected from these ecosystems after wildfire and prescribed burns showed a significant decrease in the Hg pool from certain reservoirs. No loss from mineral soil was observed for the study areas but data from fire severity points suggested that Hg in the upper few millimeters of surface soil may be volatilized due to exposure to elevated temperatures. Comparison of data from burned and unburned plots suggested that the only significant source of atmospheric Hg from the prescribed burn was combustion of litter. Differences in unburned versus burned Hg reservoirs at the forest wildfire site demonstrated that drastic reduction in the litter and above ground live biomass Hg reservoirs after burning had occurred. Sagebrush and litter were absent in the burned plots after a wildfire suggesting that both reservoirs were released during the fire. Mercury emissions due to fire from the forest prescribed burn, forest wildfire, and sagebrush steppe wildfire sites were roughly estimated at 2.0 to 5.1, 2.2 to 4.9, and 0.36±0.13 g ha−1, respectively, with litter and vegetation being the most important sources.

Mercury in smoke from biomass fires

Litter and green vegetation were collected in 7 locations in the contiguous United States, analyzed for mercury, and burned under controlled conditions at the US Forest Service Fire Science laboratory in Missoula, MT. Among fuels, leaf and 3needle litter contained the highest concentration (up to 71ng/g on dry weight) of mercury. The combustion of litter and green vegetation resulted in essentially complete release of mercury stored in the fuel. Mercury is emitted primarily as elemental mercury, >95% for most burns, with particulate mercury (TPM) accounting for the remainder. From the laboratory experiments we project that mercury emitted from temperate/boreal forest fires and from all biomass burning is an important source components for the atmospheric mercury budget.