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In this study, ash transformation and release of critical ash-forming elements during single-pellet combustion of different types of agricultural opportunity fuels were investigated. The work focused on potassium (K) and phosphorus (P). Single pellets of poplar, wheat straw, grass, and wheat grain residues were combusted in a macro-thermogravimetric analysis reactor at three different furnace temperatures (600, 800, and 950 °C). In order to study the transformation of inorganic matters at different stages of the thermal conversion process, the residues were collected before and after full devolatilization, as well as after complete char conversion. The residual char/ash was characterized by scanning electron microscopy-energy-dispersive X-ray spectroscopy, X-ray diffraction, inductively coupled plasma, and ion chromatography, and the interpretation of results was supported by thermodynamic equilibrium calculations. During combustion of poplar, representing a Ca-K-rich woody energy crop, the main fraction of K remained in the residual ash primarily in the form of K2Ca(CO3)2 at lower temperatures and in a K-Ca-rich carbonate melt at higher temperatures. Almost all P retained in the ash and was mainly present in the form of hydroxyapatite. For the Si-K-rich agricultural biomass fuels with a minor (wheat straw) or moderate (grass) P content, the main fraction of K remained in the residual ash mostly in K-Ca-rich silicates. In general, almost all P was retained in the residual ash both in K-Ca-P-Si-rich amorphous structures, possibly in phosphosilicate-rich melts, and in crystalline forms as hydroxyapatite, CaKPO4, and calcium phosphate silicate. For the wheat grain, representing a K-P-rich fuel, the main fraction of K and P remained in the residual ash in the form of K-Mg-rich phosphates. The results showed that in general for all studied fuels, the main release of P occurred during the devolatilization stage, while the main release of K occurred during char combustion. Furthermore, less than 20% of P and 35% of K was released at the highest furnace temperature for all fuels.

Residential biomass combustion is a significant source of aerosol particles on regional and global scales influencing climate and human health. The main objective of the current study was to investigate the properties of cloud condensation nuclei (CCN) emitted from biomass burning of solid fuels in different cookstoves mostly of relevance to Sub-Saharan East Africa. The traditional 3-stone fire (3S) and a rocket stove (RS) were used for combustion of wood logs of sesbania (ses) and casuarina (cas) with birch (bir) used as a reference. A natural draft (ND) and a forced draft (FD) pellet stove were used for combustion of pelletized sesbania and pelletized Swedish softwood (sw) alone or in mixtures with pelletized coffee husk (ch), rice husk (rh) or water hyacinth (wh). The CCN activity and the effective density were measured for particles with mobility diameters of ∼65, ∼100 and ∼200 nm, respectively, and occasionally for ∼350 nm particles. Particle number size distributions were measured online with a fast particle analyzer. The chemical composition of the fuel ash was measured by application of standard protocols. The average particle number size distributions were by number typically dominated by an ultrafine mode, and in most cases a soot mode was centered around a mobility diameter of ∼150 nm. The CCN activities decreased with increasing particle size for all experiments and ranged in terms of the hygroscopicity parameter, κ, from ∼0.1 to ∼0.8 for the ultrafine mode and from ∼0.0 to ∼0.15 for the soot mode. The CCN activity of the ultrafine mode increased with increasing combustion temperature for a given fuel, and it typically increased with increasing potassium concentration in the investigated fuels. The primary CCN and the estimated particulate matter (PM) emission factors were typically found to increase significantly with increasing potassium concentration in the fuel for a given stove. In order to link CCN emission factors to PM emission factors, knowledge about stove technology, stove operation and the inorganic fuel ash composition is needed. This complicates the use of ambient PM levels alone for estimation of CCN concentrations in regions dominated by biomass combustion aerosol, with the relation turning even more complex when accounting for atmospheric ageing of the aerosol.

The ongoing transition to renewable fuel sources has led to increased use of wood and other biomass fuels. The physiochemical characteristics of biomass combustion derived aerosols depends on appliances, fuel and operation procedures, and particles generated during incomplete combustion are linked to toxicity. Frequent indoor wood burning is related to severe health problems such as negative effects on airways and inflammation, as well as chronic hypoxia and pathological changes in placentas, adverse pregnancy outcome, preterm delivery and increased risk of preeclampsia. The presence of combustion-derived black carbon particles at both the maternal and fetal side of placentas suggests that particles can reach the fetus. Air pollution particles have also been shown to inhibit trophoblast migration and invasion, which are vital functions for the development of the placenta during the first trimester. In this study we exposed a placental first trimester trophoblast cell line to wood smoke particles emitted under Nominal Burn rate (NB) or High Burn rate (HB). The particles were visible inside exposed cells and localized to the mitochondria, causing ultrastructural changes in mitochondria and endoplasmic reticulum. Exposed cells showed decreased secretion of the pregnancy marker human chorionic gonadotropin, increased secretion of IL-6, disrupted membrane integrity, disrupted proliferation and contained specific polycyclic aromatic hydrocarbons (PAHs) from the particles. Taken together, these results suggest that wood smoke particles can enter trophoblasts and have detrimental effects early in pregnancy by disrupting critical trophoblast functions needed for normal placenta development and function. This could contribute to the underlying mechanisms leading to pregnancy complications such as miscarriage, premature birth, preeclampsia and/or fetal growth restriction. This study support the general recommendation that more efficient combustion technologies and burning practices should be adopted to reduce some of the toxicity generated during wood burning.

Emissions from small-scale residential biomass combustion are a major source of indoor and outdoor particulate matter (PM) air pollution, and the performance of stoves, boilers, and fireplaces have been shown to be influenced both by fuel properties, technology, and user behavior (firing procedures). Still, rather scarce information is available regarding the relative importance of these variables for the particle characteristics and emissions of different particulate components, e.g., soot, polycyclic aromatic hydrocarbons (PAHs), oxy-PAH, and metals. In particular, the behavior of different wood fuels under varying firing procedures and combustion conditions has not been studied thoroughly. Therefore, the objective of this work was to elucidate the influence of wood species and combustion conditions on particle emission characteristics in a typical Nordic residential wood stove. The emissions from four different wood species were investigated at two controlled combustion conditions, including nominal an...

Over 640 million people in Africa are expected to rely on solid-fuels for cooking by 2040. In Western Kenya, cooking inefficiently persists as a major cause of burden of disease due to household air pollution. Efficient biomass cooking is a local-based renewable energy solution to address this issue. The Life-Cycle Assessment tool Simapro 8.5 is applied for analyzing the environmental impact of four biomass cooking strategies for the Kisumu County, with analysis based on a previous energy modelling study, and literature and background data from the Ecoinvent and Agrifootprint databases applied to the region. A Business-As-Usual scenario (BAU) considers the trends in energy use until 2035. Transition scenarios to Improved Cookstoves (ICS), Pellet-fired Gasifier Stoves (PGS) and Biogas Stoves (BGS) consider the transition to wood-logs, biomass pellets and biogas, respectively. An Integrated (INT) scenario evaluates a mix of the ICS, PGS and BGS. In the BGS, the available biomass waste is sufficient to be upcycled and fulfill cooking demands by 2035. This scenario has the lowest impact on all impact categories analyzed followed by the PGS and INT. Further work should address a detailed socio-economic analysis of the analyzed scenarios.

Ice nucleating abilities of particulate emissions from solid-fuel burning cookstoves were studied using a portable ice nuclei counter SPIN (SPectrometer for Ice Nuclei) as part of the SUSTAINE (Salutary Umeå STudy of Aerosols IN Biomass Cookstove Emissions) laboratory experiment campaign. The emissions were generated from two traditional cookstove types commonly used for household cooking in sub-Saharan Africa, and two advanced gasifier stoves which are under research to promote sustainable development alternatives. The studied solid fuels included biomass from two different African tree species, Swedish softwood and agricultural residue products relevant to the region. Measurements were performed with a modified version of the standard water boiling test on (1) polydisperse samples from flue gas during burning and (2) size-selected accumulation mode (250–500 nm) soot particles from a 15-m3 aerosol-storage chamber, from which the particles were introduced to water-supersaturated freezing conditions in the SPIN. We observed that accumulation mode soot particles generally produced an ice-activated fraction of 10−3 in temperatures that were 1–1.5 °C higher than what was required for homogeneous freezing at fixed RHwater = 115 %. Five special experiments where the combustion performance of one cookstove was intentionally modified were also performed, which led to a significant increase in the ice nucleating ability of the particles in two experiments, resulting in 10−3 ice activation at up to 5.9 °C higher temperatures than homogeneous freezing. Moreover, six different physico-chemical properties of the emission particles were investigated but we did not find a clear correlation between them and increasing ice-nucleating ability. We conclude that in general, the studied freshly emitted combustion aerosols only facilitate immersion freezing at temperatures moderately above where homogeneous freezing occurs.

Introduction: Biomass combustion emissions contribute to indoor and outdoor air pollution. Exposure to wood smoke has been associated with development and worsening of respiratory diseases such as asthma and COPD, but also increases in airway infections. The mechanisms behind these effects are not fully clear. Aim and Objectives: To evaluate effects on lymphocyte subtypes and activity markers in peripheral blood from healthy subjects by controlled wood smoke exposure. Methods: Fourteen healthy subjects participated in a randomized, double-blind crossover study with exposures to sooty wood smoke and filtered air for two hours, on two occasions. Blood sampling for flow cytometry was performed 6 hours after each exposure. Peripheral blood cells were stained with fluorochrome-conjugated antibodies for CD3, CD4, CD8, CD25, CD127, CD69, CD56 and CD16. Results: Total lymphocyte numbers were increased 6 hours post wood smoke exposure, as were CD3+, CD4+ and CD8+ cells, along with the numbers of CD8+ cells expressing CD56CD16 vs filtered air. On CD4+ and CD8+ cells the CD69 and CD25 activation marker expressions were increased after wood smoke exposure, as were regulatory T cells. Conclusions: Short-term exposure to wood smoke recruited and activated CD4 and CD8 cells to the peripheral blood as a systemic response to the noxious challenge. These findings may be of importance for adverse health effects by wood smoke, especially after long-term exposure.

Background: Biomass smoke is associated with adverse health effects on the respiratory system, including increased asthma morbidity and worsening of symptoms leading to emergency room visits. Aims and Objectives: The aim of this study was to investigate whether controlled exposure to wood smoke generated from incomplete soot-rich combustion would increase small airway resistance and reactance. Methods: Fifteen healthy subjects (20-45 ys) underwent controlled chamber exposure on two occasions to filtered air and to sooty wood smoke (PM1 ~ 450 μg/m3), generated by a common Swedish wood stove firing birch logs. The study was performed in a double-blind, randomized cross-over fashion and the subjects alternated between exercise (VE=20 L/min/m2) and rest at 15-minute intervals for 2 hours. Forced Oscillation Technique (FOT) (tremoFlo®, THORASYS) was used to determine airway resistance and reactance before and after exposure to wood smoke as well as before and after exposure to filtered air. Results: Both airway reactance (P Conclusions: Short term exposure to sooty wood smoke did not affect small airways resistance or reactance as determined using FOT in healthy subjects. Further research should study the effects in asthmatic populations, and also whether repeated exposures are needed to cause the small airways effects indicated by population-based studies.

Background: Exposure to emissions from biomass burning contributes to respiratory diseases, including obstructive airway diseases, acute lower respiratory tract infections and tuberculosis. The underlying mechanisms effects are not well understood. Aims and Objectives: To determine if exposure to wood smoke from incomplete combustion would elicit DNA damage on airway cells and epithelial cell lines. Methods: Fourteen healthy subjects underwent controlled chamber exposure on two occasions to filtered air and to sooty wood smoke (PM1 ~ 450 μg/m3), generated by a Swedish wood stove firing birch logs, according to double-blind randomized cross-over design. The subjects alternated exercise (VE=20 L/min/m2) and rest at 15-minute intervals for 2 hours. Bronchoscopies with sampling of bronchial wash (BW) and bronchoalveolar lavage (BAL) were performed 6 hours after exposure. Furthermore, alveolar type II cell line A549 and bronchial epithelial cell line BEAS-2B were exposed to wood smoke particles at four different doses. DNA damage was examined with the Comet assay and olive tail moment (OTM) was quantified. Results: Eosinophil numbers was increased in BAL after exposure to wood smoke, with no changes in other cells. Moreover, there was a dose-dependent increase in DNA damage in vitro when comparing PM concentrations above 75µg ml-1 to air. Conclusion: Short term exposure to sooty wood smoke induced a bronchoalveolar eosinophilic insult. This may link with the development and worsening of asthma after chronic exposure to wood smoke. Moreover, the observed DNA damage in vitro may explain the previously shown reduction in airway cells, which in turn may causally affect cellular immunity and increase the incidence of respiratory infection

Traditional cooking is today's largest global environmental health risk. Over 640 million people in Africa are expected to rely on biomass for cooking by 2040. In Kenya, cooking inefficiently with ...

Time-resolved particle emissions from a conventional wood stove were investigated with aerosol mass spectrometry to provide links between combustion conditions, emission factors, mixing state of refractory black carbon and implications for organic tracer methods. The addition of a new batch of fuel results in low temperature pyrolysis as the fuel heats up, resulting in strong, short-lived, variable emission peaks of organic aerosol-containing markers of anhydrous sugars, such as levoglucosan (fragment at m/z 60). Flaming combustion results in emissions dominated by refractory black carbon co-emitted with minor fractions of organic aerosol and markers of anhydrous sugars. Full cycle emissions are an external mixture of larger organic aerosol-dominated and smaller thinly coated refractory black carbon particles. A very high burn rate results in increased full cycle mass emission factors of 66, 2.7, 2.8 and 1.3 for particulate polycyclic aromatic hydrocarbons, refractory black carbon, total organic aerosol and m/z 60, respectively, compared to nominal burn rate. Polycyclic aromatic hydrocarbons are primarily associated with refractory black carbon-containing particles. We hypothesize that at very high burn rates, the central parts of the combustion zone become air starved, leading to a locally reduced combustion temperature that reduces the conversion rates from polycyclic aromatic hydrocarbons to refractory black carbon. This facilitates a strong increase of polycyclic aromatic hydrocarbons emissions. At nominal burn rates, full cycle emissions based on m/z 60 correlate well with organic aerosol, refractory black carbon and particulate matter. However, at higher burn rates, m/z 60 does not correlate with increased emissions of polycyclic aromatic hydrocarbons, refractory black carbon and organic aerosol in the flaming phase. The new knowledge can be used to advance source apportionment studies, reduce emissions of genotoxic compounds and model the climate impacts of refractory black carbon, such as absorption enhancement by lensing. (C) 2017 The Authors. Published by Elsevier Ltd.

The aim was to identify relationships between combustion conditions, particle characteristics, and optical properties of fresh and photochemically processed emissions from biomass combustion. The combustion conditions included nominal and high burn rate operation and individual combustion phases from a conventional wood stove. Low temperature pyrolysis upon fuel addition resulted in "tar-ball" type particles dominated by organic aerosol with an absorption Angstro exponent (AAE) of 2.5−2.7 and estimated Brown Carbon contributions of 50−70% to absorption at the climate relevant aethalometer-wavelength (520 nm). High temper- ature combustion during the intermediate (flaming) phase was dominated by soot agglomerates with AAE 1.0−1.2 and 85− 100% of absorption at 520 nm attributed to Black Carbon. Intense photochemical processing of high burn rate flaming combustion emissions in an oxidation flow reactor led to strong formation of Secondary Organic Aerosol, with no or weak absorption. PM1 mass emission factors (mg/kg) of fresh emissions were about an order of magnitude higher for low temperature pyrolysis compared to high temperature combustion. However, emission factors describing the absorption cross section emitted per kg of fuel consumed (m 2 /kg) were of similar magnitude at 520 nm for the diverse combustion conditions investigated in this study. These results provide a link between biomass combustion conditions, emitted particle types, and their optical properties in fresh and processed plumes which can be of value for source apportionment and balanced mitigation of biomass combustion emissions from a climate and health perspective.

One of the most stringent intensity limitations on medium energy accelerator experiments using foil-contained gas target chambers has been the apparent impossibility of putting large currents through the entrance foil without melting it. It has been found, however, that if a 0.05-mil nickel foil is suitably cooled by a jet or cold gas, currents as high as 20 mu a of 2-Mev protons may be used. The cooling jet is made from a piece of one-eighth-in-- diam. copper tubing modified to yield a jet of gas for cross section one quarter inch by twenty mils. The target gas is used as the cooling gas. The helium gas used flows from a tank through copper tubing immersed in liquid nitrogen, into the target chamber, and then out through a vacuum pump. (A.C.)