Modified Combustion Efficiency Research Articles

Emission Factors of Polycyclic Aromatic Hydrocarbons and Oxidative Potential of Fine Particles Emitted from Crop Residues Burning

Mexico displays significant agricultural activity that, in notorious instances unfolds closely associated with undesirable burning practices of crop residues, which could rise climate change and cause adverse effects to human health, due to emission of fine particles (PM2.5). PM2.5 contain organic compounds such as quinones, soluble organic carbon and polycyclic aromatic hydrocarbons (PAHs), which can be associated to carcinogenic and mutagenic diseases and in some cases to cellular oxidative stress. Presently, we carried out simulation burning of crop residues in an open burning to collect PM2.5 samples by an isokinetic methodology (Method 201a of Environmental Protection Agency). The NIOSH870 method was used to quantify organic carbon (OC) and elemental carbon (EC) fractions. PAHs from PM2.5 were extracted and analyzed by gas chromatography-mass spectrometry while the oxidative potential was measured through the dithiothreitol (DTT) consumption and PM2.5 concentration. The results showed that OC fractions concentration are associated with the modified combustion efficiency (MCE). The most abundant fractions were OC1 and OC2. Emission factors of the sum of 18 PAHs (ƩPAHs) showed a large variation between crops; from 0.49 mg kg−1-fuel (for barley) to 9.16 mg kg−1-fuel (for cotton), then, a single emission factor that includes the burning of all crop residues should not be considered, since the emission factor varies according with the type of biomass burned. Whereas PAHs of 4-6 rings (> 97%) were the most abundant, the concentrations of carcinogenic and mutagenic PAHs accounted for 60% of the sum of all PAHs concentrations. Some diagnostic ratios were identified, but these varied between crops. Burning of residues with low combustion efficiencies presented the highest oxidative potential, such as cotton and sorghum. Oxidative potential correlated with OC concentration, but not with PAHs, suggesting the presence of other compounds.

Characterization of Emissions and Residue from Measures to Improve Efficiency of In Situ Oil Burns

ABSTRACT NUMBER: 1141223 Simulated in situ oil burning tests were conducted in a 14 m × 2.4 m × 2.4 m tank to characterize variations in boom length/width aspect ratios, the use of injection air, nozzle angle, and presence or absence of waves on combustion efficiency. Tests were done with approximately 35 L of unweathered Alaska North Slope oil within an outdoor, fresh water, 63 m3 tank. The combustion plume was sampled with a crane-suspended instrument system. Emission measurements quantified carbon monoxide, carbon dioxide, particulate matter less than 2.5 μm (PM2.5), and total carbon. Post-burn residue samples were collected with pre-weight oil absorbent to determining oil mass loss and total petroleum hydrocarbons (TPH) in the residue. Plume measurements of modified combustion efficiencies (MCET) ranged from 85% to 93%. Measurement of residual, unburnt oil showed that the oil mass loss ranged from 89% to 99%. A three-fold variation in PM2.5 emission factors was observed from the test conditions where the emission factors decreased with increased MCE. The TPH in the residue were found to decrease with increased oil mass loss percentage. In terms of combustion efficiency and oil consumption, results suggest that the most effective burns were those that have high length to width boom aspect ratios and added injection air.

Spatially Resolved Emission Factors to Reduce Uncertainties in Air Pollutant Emission Estimates from the Residential Sector.

The residential sector is a major source of air pollutant emission inventory uncertainties. A nationwide field emission measurement campaign was conducted in rural China to evaluate the variabilities of realistic emission factors (EFs) from indoor solid fuel combustion. For a total of 1313 burning events, the overall average EFs (±standard deviation) of PM2.5 were 8.93 ± 6.95 and 7.33 ± 9.01 g/kg for biomass and coals, respectively, and 89.3 ± 51.2 and 114 ± 87 g/kg for CO. Higher EFs were found from burning of uncompressed straws, while lower EFs were found from processed biomass pellets, coal briquettes, and relatively clean anthracite coals. Modified combustion efficiency was found to be the most significant factor associated with variations in CO EFs, whereas for PM2.5, fuel and stove differences determined its variations. Weak correlations between PM2.5 and CO indicated high uncertainties in using CO as a surrogate for PM2.5. EFs accurately fit log-normal distributions, and obvious spatial heterogeneity was observed attributed to different fuel-stove combinations across the country. Emission estimation variabilities, which are determined by the interquartile ranges divided by the median values, were notably reduced when spatially resolved EFs were adopted in the inventory.

Intraseasonal variability of greenhouse gas emission factors from biomass burning in the Brazilian Cerrado

Abstract. Landscape fires, often referred to as biomass burning (BB), emit substantial amounts of (greenhouse) gases and aerosols into the atmosphere each year. Frequently burning savannas, mostly in Africa, Australia, and South America are responsible for over 60 % of total BB carbon emissions. Compared to many other sources of emissions, fires have a strong seasonality. Previous research has identified the mitigation potential of prescribed fires in savanna ecosystems; by burning cured fuels early in the dry season when landscape conditions still provide moist buffers against fire spread, fires are in general smaller, patchier, and less intense. While it is widely accepted that burned area (BA) and the total carbon consumed are lower when fires are ignited early in the dry season, little is known about the intraseasonal variability of emission factors (EFs). This is important because potentially, higher EFs in the early dry season (EDS) could offset some of the carbon benefits of EDS burning. Also, a better understanding of EF intraseasonal variability may improve large-scale BB assessments, which to date rely on temporally static EFs. We used a sampling system mounted on an unmanned aerial vehicle (UAV) to sample BB smoke in the Estação Ecológica Serra Geral do Tocantins in the Brazilian states of Tocantins and Bahia. The protected area contains all major Cerrado vegetation types found in Brazil, and EDS burning has been implemented since 2014. Over 800 smoke samples were collected and analysed during the EDS of 2018 and late dry season (LDS) of 2017 and 2018. The samples were analysed using cavity ring-down spectroscopy, and the carbon balance method was used to estimate CO2, CO, CH4, and N2O EFs. Observed EF averages and standard deviations were 1651 (±50) g kg−1 for CO2, 57.9 (±28.2) g kg−1 for CO, 0.97 (±0.82) g kg−1 for CH4, and 0.096 (±0.174) g kg−1 for N2O. Averaged over all measured fire prone Cerrado types, the modified combustion efficiency (MCE) was slightly higher in the LDS (0.961 versus 0.956), and the CO and CH4 were 10 % and 2.3 % lower in the LDS compared to the EDS. However, these differences were not statistically significant using a two-tailed t test with unequal variance at a 90 % significance level. The seasonal effect was larger in more wood-dominated vegetation types. N2O EFs showed a more complex seasonal dependency, with opposite intraseasonal trends for savannas that were dominated by grasses versus those with abundant shrubs. We found that the N2O EF for the open Cerrado was less than half the EF suggested by literature compilations for savannas. This may indicate a substantial overestimation of the contribution of fires in the N2O budget. Overall, our data imply that in this region, seasonal variability in greenhouse gas emission factors may offset only a small fraction of the carbon mitigation gains in fire abatement programmes.

Emissions of Reactive Nitrogen From Western U.S. Wildfires During Summer 2018

AbstractReactive nitrogen (Nr) within smoke plumes plays important roles in the production of ozone, the formation of secondary aerosols, and deposition of fixed N to ecosystems. The Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE‐CAN) field campaign sampled smoke from 23 wildfires throughout the western U.S. during summer 2018 using the NSF/NCAR C‐130 research aircraft. We empirically estimate Nr normalized excess mixing ratios and emission factors from fires sampled within 80 min of estimated emission and explore variability in the dominant forms of Nr between these fires. We find that reduced N compounds comprise a majority (39%–80%; median = 66%) of total measured reactive nitrogen (ΣNr) emissions. The smoke plumes sampled during WE‐CAN feature rapid chemical transformations after emission. As a result, within minutes after emission total measured oxidized nitrogen (ΣNOy) and measured total ΣNHx (NH3 + pNH4) are more robustly correlated with modified combustion efficiency (MCE) than NOx and NH3 by themselves. The ratio of ΣNHx/ΣNOy displays a negative relationship with MCE, consistent with previous studies. A positive relationship with total measured ΣNr suggests that both burn conditions and fuel N content/volatilization differences contribute to the observed variability in the distribution of reduced and oxidized Nr. Additionally, we compare our in situ field estimates of Nr EFs to previous lab and field studies. For similar fuel types, we find ΣNHx EFs are of the same magnitude or larger than lab‐based NH3 EF estimates, and ΣNOy EFs are smaller than lab NOx EFs.

Airborne measurements of fire emission factors for African biomass burning sampled during the MOYA campaign

Abstract. Airborne sampling of methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), and nitrous oxide (N2O) mole fractions was conducted during field campaigns targeting fires over Senegal in February and March 2017 and Uganda in January 2019. The majority of fire plumes sampled were close to or directly over burning vegetation, with the exception of two longer-range flights over the West African Atlantic seaboard (100–300 km from source), where the continental outflow of biomass burning emissions from a wider area of West Africa was sampled. Fire emission factors (EFs) and modified combustion efficiencies (MCEs) were estimated from the enhancements in measured mole fractions. For the Senegalese fires, mean EFs and corresponding uncertainties in units of gram per kilogram of dry fuel were 1.8±0.19 for CH4, 1633±171.4 for CO2, and 67±7.4 for CO, with a mean MCE of 0.94±0.005. For the Ugandan fires, mean EFs were 3.1±0.35 for CH4, 1610±169.7 for CO2, and 78±8.9 for CO, with a mean modified combustion efficiency of 0.93±0.004. A mean N2O EF of 0.08±0.002 g kg−1 is also reported for one flight over Uganda; issues with temperature control of the instrument optical bench prevented N2O EFs from being obtained for other flights over Uganda. This study has provided new datasets of African biomass burning EFs and MCEs for two distinct study regions, in which both have been studied little by aircraft measurement previously. These results highlight the important intracontinental variability of biomass burning trace gas emissions and can be used to better constrain future biomass burning emission budgets. More generally, these results highlight the importance of regional and fuel-type variability when attempting to spatially scale biomass burning emissions. Further work to constrain EFs at more local scales and for more specific (and quantifiable) fuel types will serve to improve global estimates of biomass burning emissions of climate-relevant gases.

Combustion and pollutant emission characteristics of argan nut shell (ANS) biomass

This paper presents an experimental study of argan nut shell (ANS) combustion in a lab-scale furnace. Biomass composition, properties and microstructures were determined. Combustion behaviour, fuel burn rate (FBR), pollutants (CO and NOx), modified combustion efficiency (MCE) and ash analysis were investigated. A comparison with wood pellets (WP) complying with the ENplus Standard was performed. The impacts of air flow rate and particle sizes on the combustion characteristics were analysed and discussed using three average ANS particle lengths: 5–8 mm, 10–18 mm and 25–30 mm. The results show that the smallest length of ANS particles induced a higher FBR and a regular distribution of the flame shapes compared to the other sizes and to wood pellets. Furthermore, the combustion temperatures, CO emission and MCE values were improved with the highest air flow rate used. CO emission was strongly affected by the operating conditions while NOx was very low for all selected cases. Elemental ash composition reveals that no ash agglomeration was observed during experiments in terms of alkali index. Moreover, the obtained ash was in the form of powder instead of agglomerated particles. This experimental investigation improves the understanding of the operational characteristics and the combustion effect of ANS biomass.

Chemical composition and light absorption of carbonaceous aerosols emitted from crop residue burning: influence of combustion efficiency

Abstract. Biomass burning is one of the major sources of carbonaceous aerosols, which affects air quality, the radiation budget and human health. Field straw residue burning is a widespread type of biomass burning in Asia, while its emissions are poorly understood compared with wood burning emissions. In this study, lab-controlled straw (wheat and corn) burning experiments were designed to investigate the emission factors and light absorption properties of different biomass burning organic aerosol (BBOA) fractions, including water-soluble organic carbon (WSOC), humic-like substances (HULIS) and water-insoluble organic carbon (WISOC). The influences of biofuel moisture content and combustion efficiency on emissions are comprehensively discussed. The emission factors of PM2.5, organic carbon (OC) and elemental carbon (EC) were 9.3±3.4, 4.6±1.9 and 0.21±0.07 g kg−1 for corn burning and 8.7±5.0, 3.9±2.8 and 0.22±0.05 g kg−1 for wheat burning, generally lower than wood or forest burning emissions. Though the mass contribution of WISOC to OC (32 %–43 %) was lower than WSOC, the light absorption contribution of WISOC (57 %–84 % at 300–400 nm) surpassed WSOC due to the higher mass absorption efficiency (MAE) of WISOC. The results suggested that BBOA light absorption would be largely underestimated if only the water-soluble fractions were considered. However, the light absorption of WSOC in the near-UV range, occupying 39 %–43 % of the total extracted OC absorption at 300 nm, cannot be negligible due to the sharper increase of absorption towards shorter wavelengths compared with WISOC. HULIS were the major light absorption contributors to WSOC, due to the higher MAE of HULIS than other high-polarity WSOC components. The emission levels and light absorption of BBOA were largely influenced by the burning conditions, indicated by modified combustion efficiency (MCE) calculated by measured CO and CO2 in this study. The emission factors of PM2.5, OC, WSOC, HULIS and organic acids were enhanced under lower MCE conditions or during higher moisture straw burning experiments. Light absorption coefficients of BBOA at 365 nm were also higher under lower MCE conditions, which was mainly due to the elevated mass emission factors. Our results suggested that the influence of varied combustion efficiency on particle emissions could surpass the differences caused by different types of biofuels. Thus, the burning efficiency or conditions should be taken into consideration when estimating the influence of biomass burning. In addition, we observed that the ratios of K+/OC and Cl-/OC increased under higher MCE conditions due to the enhancement of potassium and chlorine released under higher fire temperatures during flaming combustion. This indicates that the potassium ion, as a commonly used biomass burning tracer, may lead to estimation uncertainty if the burning conditions are not considered.

Efficiency of improved cookstoves and emission of Carbon Monoxide and Carbon Dioxide: An intervention study in Northern Ghana

Title: Efficiency of improved cookstoves and emission of Carbon Monoxide and Carbon Dioxide: an intervention study in Northern Ghana AbstractBiomass burning for home energy use is a major environmental health concern. Improved cooking technologies could generate environmental health benefits, yet prior results regarding reduced exposure to air pollution from improve cookstoves are mixed. In this study, 20 in-field uncontrolled cooking tests were conducted in domestic settings to assess the emission and efficiency of the Ace and the Jumbo stoves using the Emission Pod (EPOD) to measure emissions in real-time. Carbon Dioxide (CO2) and Carbon Monoxide (CO) emissions, Emission Factors (EF), Modified Combustion Efficiency (MCE) and Cooking time were all calculated across a variety of meal types using the two stoves. Overall average CO emission was estimated at 248.71±44.66 ppm for the Ace stove while that of the Jumbo stove was calculated to be 103.66±24.4 ppm (P=0.024). The Jumbo stove had a higher MCE of 0.93 against the Ace stove (0.84). Using the partial capture Carbon Balance Method (CBM), EF was calculated for both stoves with the Ace recording a CO EF of 1425.04 g/kg and CO2 EF of 1318.35 g/kg. The Jumbo, on the other hand, had a CO EF of 151.57 g/kg and a CO2 EF of 1215.82 g/kg. The study concluded that although the stoves had better performance in most of the parameters studied compared to other stove interventions in the literature, they still fell short when compared with some of the traditional cooking methods. While the Jumbo falls within the International Workshop Agreement (IWA) tier 4 category guidelines for cookstove, the Ace stove which is much fancier falls in WHO-IWA category 0.

Standoff detection of chemical plumes from high explosive open detonations using a swept-wavelength external cavity quantum cascade laser

A swept-wavelength external cavity quantum cascade laser (ECQCL) is used to perform standoff detection of combustion gases in a plume generated from an outdoor high-explosive (HE) open detonation. The swept-ECQCL system was located at a standoff distance of 830 m from a 41 kg charge of LX-14 (polymer-bonded high explosive) and was used to measure the infrared transmission/absorption through the post-detonation plume as it propagated through the beam path. The swept-ECQCL was operated continuously to record broadband absorption spectra at a 200 Hz rate over a spectral range from 2050 to 2230 cm−1 (4.48–4.88 μm). Fitting of measured spectra was used to determine time-resolved column densities of CO, CO2, H2O, and N2O. Analysis of visible video imagery was used to provide timing correlations and to estimate plume dimensions, from which gas mixing ratios were estimated. Measured emission factors and modified combustion efficiency show good agreement with previously reported values.

Light absorption properties and absorption emission factors for indoor biomass burning

The optical properties of light-absorbing carbonaceous aerosols have caused increasing concerns due to their significant impacts on local and regional climates. In this study, particles from biomass burning in home stoves were collected and evaluated for their optical properties. The absorption Ångström exponent (AAE) values ranged from 1.17 to 2.92 and negatively correlated with the modified combustion efficiency, indicatinging more brown carbon in combustion emissions with relatively low combustion efficiencies. The average contribution of brown carbon to the total aerosol absorption at 370 nm was equally as important as that of black carbon (BC), with the average relative contribution fraction of 50% varying from 10% to 84% for different biomasses. The average value of the mass absorption efficiency (MAE) of BC (MAEBC) at 880 nm was positively correlated with the ratio of organic carbon to elemental carbon, indicating the significant coating effects of organic aerosols. The MAE values of BrC at 370 nm were in the range of 1.1–11.3 m2/g, with an average of 5.1 ± 2.2 m2/g. The estimated absorption emission factors at 370 nm and 880 nm were 3.75 ± 3.45 and 0.84 ± 0.78 m2/kg, respectively. Optical property information of particles emitted from real-world biomass burning are imperative in future modeling studies of biomass burning impacts on climate. The limitation of the relatively small sample size for each subgroup fuel calls for more field- and lab-based emission characterization research.

Evaluating co-emissions into indoor and outdoor air of EC, OC, and BC from in-home biomass burning

Biomass burning constitutes a major source of ambient PM2.5 but also a predominant source of indoor PM2.5. Carbonaceous matters, such as organic carbon (OC), elemental carbon (EC), black carbon, and brown carbon (BrC), are major components of PM2.5, and are of broad concern due to their significant impacts on health and climate patterns. In this study, we took simultaneous indoor and outdoor emission measurements to quantify pollutant emission factors (EFs) of carbonaceous matters, including the stack and fugitive EFs, from the real-world biomass burning in rural households. Modified combustion efficiency, fuel moisture, burning rates, and chimney gas velocity explained 45–71% of variations in the field-based emission factors. BrC (measured at 370 nm, and estimated based on the specific attenuation coefficients-16.6 m2/g at 880 nm and 39.5 m2/g at 370 nm) comprised up to ~20% of all OC. Fractions of fugitive emissions of the total reached as high as 44–48%. Fugitive emissions would result in very high peak concentrations of approximately tens of mg/m3, leading to severe indoor air pollution. The study clearly demonstrates that the simultaneous studies on indoor and outdoor emissions and air quality is crucial to understand mechanisms of the environmental impacts of internal combustion sources.

Laboratory studies of fresh and aged biomass burning aerosol emitted from east African biomass fuels – Part 1: Optical properties

Abstract. An accurate measurement of the optical properties of aerosol is critical for quantifying the effect of aerosol on climate. Uncertainties persist and results of measurements vary significantly. Biomass burning (BB) aerosol has been extensively studied through both field and laboratory environments for North American fuels to understand the changes in optical and chemical properties as a function of aging. There is a need for a wider sampling of fuels from different regions of the world for laboratory studies. This work represents the first such study of the optical and chemical properties of wood fuel samples commonly used for domestic purposes in east Africa. In general, combustion temperature or modified combustion efficiency (MCE) plays a major role in the optical properties of the emitted aerosol. For fuels combusted with MCE of 0.974±0.015, which is referred to as flaming-dominated combustion, the single-scattering albedo (SSA) values were in the range of 0.287 to 0.439, while for fuels combusted with MCE of 0.878±0.008, which is referred to as smoldering-dominated combustion, the SSA values were in the range of 0.66 to 0.769. There is a clear but very small dependence of SSA on fuel type. A significant increase in the scattering and extinction cross section (with no significant change in absorption cross section) was observed, indicating the occurrence of chemistry, even during dark aging for smoldering-dominated combustion. This fact cannot be explained by heterogeneous oxidation in the particle phase, and we hypothesize that secondary organic aerosol formation is potentially happening during dark aging. After 12 h of photochemical aging, BB aerosol becomes highly scattering with SSA values above 0.9, which can be attributed to oxidation in the chamber. Aging studies of aerosol from flaming-dominated combustion were inconclusive due to the very low aerosol number concentration. We also attempted to simulate polluted urban environments by injecting volatile organic compounds (VOCs) and BB aerosol into the chamber, but no distinct difference was observed when compared to photochemical aging in the absence of VOCs.

Emissions from the Open Laboratory Combustion of Cheatgrass (Bromus Tectorum)

Cheatgrass (Bromus Tectorum) is a highly invasive species in the Great Basin of the Western USA that is increasing the frequency and intensity of wildland fires. Though cheatgrass plays a significant role in the fire ecology of the Great Basin, very little is known about its combustion emissions. The fresh smoke from 16 open laboratory burns of cheatgrass was analyzed using real-time measurements and filter analysis. We presented measured intensive optical properties of the emitted smoke, including absorption Ångström exponent (AAE), scattering Ångström exponent (SAE), single scattering albedo (SSA), and other combustion properties, such as modified combustion efficiency (MCE) and fuel-based emission factors (EFs). In addition, we gave a detailed chemical analysis of polar organic species in cheatgrass combustion emissions. We presented EFs that showed a large variation between fuels and demonstrated that analysis of combustion emissions for specific fuels was important for studying and modeling the chemistry of biomass-burning emissions.

HONO Emissions from Western U.S. Wildfires Provide Dominant Radical Source in Fresh Wildfire Smoke.

Wildfires are an important source of nitrous acid (HONO), a photolabile radical precursor, yet in situ measurements and quantification of primary HONO emissions from open wildfires have been scarce. We present airborne observations of HONO within wildfire plumes sampled during the Western Wildfire Experiment for Cloud chemistry, Aerosol absorption and Nitrogen (WE-CAN) campaign. ΔHONO/ΔCO close to the fire locations ranged from 0.7 to 17 pptv ppbv-1 using a maximum enhancement method, with the median similar to previous observations oftemperate forest fire plumes. Measured HONO to NOx enhancement ratios were generally factors of 2, or higher, at early plume ages than previous studies. Enhancement ratios scale with modified combustion efficiency and certain nitrogenous trace gases, which may be useful to estimate HONO release when HONO observations are lacking or plumes have photochemical exposures exceeding an hour as emitted HONO is rapidly photolyzed. We find that HONO photolysis is the dominant contributor to hydrogen oxide radicals (HOx = OH + HO2) in early stage (<3 h) wildfire plume evolution. These results highlight the role of HONO as a major component of reactive nitrogen emissions from wildfires and the main driver of initial photochemical oxidation.

Emissions of gaseous pollutants from laboratory-based fires of vegetation from five common vegetation types in Western Australia

This study investigated emission factors (EFs) for CO2, CO, NO and carbonyls from laboratory-based combustion of five typical vegetation types of Western Australia. A range of combustion conditions was obtained by controlling the vegetation moisture content and air flow rate. CO2, CO and NO were measured using a multi-gas monitor MultiRAE. Six carbonyls were collected using 2,4-DNPH sorbent tubes and analysed using HPLC-UV.Burns of woodland (Banksia) and forest (Jarrah) had significantly higher EFCO, with lower modified combustion efficiency (MCE) than those of tropical grass (Spinifex). Temperate grass (Veldt) fires had lower EFCO2 and higher EFCO and EFcarbonyls, and a much lower MCE than those of the tropical grass fires. EFNO were similar for woodland, forest and tropical grass but large differences in EFNO were observed for Spinifex and Veldt grass. Formaldehyde was the most abundant carbonyl emitted.Combustion conditions influenced the EFcarbonyls with larger EFs from burns with higher fuel moisture contents and/or at higher flow rates. Functions to extrapolate EFs for infrequently measured carbonyls (acetaldehyde, acetone and propionaldehyde) from EFformaldehyde were developed. The EFCO2 and EFCO were similar to values reported from field measurements for similar ecosystems in Australia, indicating the applicability of these laboratory-based results. EFs for other gases differed to those reported from bushfires in other parts of the world suggesting that to improve prediction of bushfire emissions and impacts in Australia, EFs of all fire-prone Australian vegetation types should be determined, particularly for those in close proximity to densely populated areas.

Field-based measurements of natural gas burning in domestic wall-mounted gas stove and estimates of climate, health and economic benefits in rural Baoding and Langfang regions of Northern China

Abstract The implementation of coal-to-gas shift in rural households for meeting people's heating and cooking demands can reduce pollutant emissions, improve indoor air quality and increase climate, health and economic co-benefits. In rural Baoding and Langfang regions of Hebei Province, China, approximately 1.25 million households have shifted from coal to natural gas combustion. Field-based emission factors, modified combustion efficiency, and thermal efficiency of typical gas stoves were measured to evaluate the contribution of this shift to local air pollution control. Natural gas burning in stoves produced much lower air pollution than coal or other popular fuel/stove combinations due to its good fuel properties and high combustion efficiency. All tested gas stoves were rated at excellent tiers according to Chinese national standards. Through the adoption of coal-to-gas shift during a complete winter heating season, the total emissions of carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), nitric oxide (NO), methane (CH4), particles with an aerodynamic diameter of ≤2.5 μm (PM2.5) and ≤10 μm (PM10) were reduced by 98%, 56%, 33%, 80%, 82%, 99% and 99% in rural Baoding region, and by 99%, 37%, 25%, 83%, 71%, 99% and 99% in rural Langfang region, respectively. Correspondingly, GWC100 values decreased from 11 396 to 4 554 and from 13 408 to 7 881 ktCO2e·heat season−1·city−1 for the two cities, respectively. The estimated 7 083, 1 142, 8 834, 3 422, and 2 464 all-cause mortality cases resulting from the intakes of CO, NO, SO2, PM2.5 and PM10 were avoided in rural Baoding region, and 5 771, 467, 7 432, 2 762 and 1 987 cases were avoided in rural Langfang region, among which cardiopulmonary death was the primary reduced mortality. The average economic benefits were 10.40 and 9.98 billion CNY (Chinese Yuan), which was equivalent to 3.19% and 3.22% of the local GDPs.

Understanding the emission pattern and source contribution of hazardous air pollutants from open burning of municipal solid waste in China

The open burning of municipal solid waste (MSW) is common in China. Therein, low–temperature anoxic combustion results in the emission of hazardous air pollutants. This study employed a dilution sampling system to conduct open burning testing on MSW samples from different functional urban areas. Additionally, modified combustion efficiency was used to distinguish smoldering and flaming combustion in two of the most common open burning practices in China: pile–up burning and barrel burning. The sampled pollutants included gaseous pollutants (e.g., CO2, CO, SO2, and NOx) and fine particles (PM2.5). This study also analyzed the carbonization compounds, 9 water–soluble ions, and 8 toxic heavy metals in PM2.5. Emission factors of air pollutants from open burning of different MSW compositions and burning modes were determined. The composition of PM2.5 from MSW open burning comprised average 43.9%, 22.5%, and 0.4% of organic carbon (OC), water–soluble ions, and toxic heavy metals (THMs), respectively. OC was found to be the primary component of PM2.5. Based on localized emission factor database, the emissions and source contribution of open burning of MSW in China were quantified. The open burning of MSW can contribute averaged 8.7%, 16.7%, 3.8%, 1.3% of PM2.5, OC, THMs, and gaseous air pollutants of reported emissions of anthropogenic sources, respectively. This work can complement current anthropogenic emission inventory and assist policy–making.

Analyzing Wildland Fire Smoke Emissions Data Using Compositional Data Techniques

AbstractBy conservation of mass, the mass of wildland fuel that is pyrolyzed and combusted must equal the mass of smoke emissions, residual char, and ash. For a given set of conditions, these amounts are fixed. This places a constraint on smoke emissions data that violates key assumptions for many of the statistical methods ordinarily used to analyze these data such as linear regression, analysis of variance, andttests. These data are inherently multivariate, relative, and nonnegative parts of a whole and are then characterized as so‐called compositional data. This paper introduces the field of compositional data analysis to the biomass burning emissions community and provides examples of statistical treatment of emissions data. Measures and tests of proportionality, unlike ordinary correlation, allow one to coherently investigate associations between parts of the smoke composition. An alternative method based on compositional linear trends was applied to estimate trace gas composition over a range of combustion efficiency that reduced prediction error by 4% while avoiding use of modified combustion efficiency as if it were an independent variable. Use of log‐ratio balances to create meaningful contrasts between compositional parts definitively stressed differences in smoke emissions from fuel types originating in the southeastern and southwestern United States. Application of compositional statistical methods as an appropriate approach to account for the relative nature of data about the composition of smoke emissions and the atmosphere is recommended.

Aerosols and carbonaceous and nitrogenous compounds emitted during the combustion of dead shrubs according to twigs’ diameter and combustion phases

Smoke from forest fires is hazardous to health and can result in losses of respiratory function and vision. The knowledge of the chemical constituents in such smoke is an important objective. In this study, leaves and branches and twigs of Cistus Monspeliensis were burned with a cone calorimeter and the emitted smoke was analysed by non-dispersive infrared (NDIR) spectroscopy, He–Ne laser method, Fourier-transform infrared (FTIR) spectroscopy, and automated thermal-desorption–gas-chromatography/mass-spectrometry (ATD-GC/MS). These techniques were used during various combustion phases: prior to ignition and during flaming and glowing phases. The influence of branch diameter on chemical composition was examined. Analysis of the smoke reveals the presence of CO2, H2O, CO, aerosols, CH4, NO, and other gases in smaller proportions, as well as non-methane organic compounds (NMOCs). 96% of the carbon present in the fuel was found in the emitted smoke. CO2 is the gas mainly emitted and its level is independent of the diameter of the cistus branch burned. It is mainly emitted in the flaming phase, unlike CO, which is emitted during the glowing phase. Aerosols are emitted principally during the pre-ignition stage. The mass loss is higher during the flaming phase than during the glowing one because the burning occurs under well-ventilated condition. During the glowing phase, the mass loss is only due to the char oxidation. The calculation of the modified combustion efficiency confirms those operating conditions.