Characterization of Carbonaceous Aerosols Emitted from Outdoor Wood Boilers

This study examines the chemical properties of carbonaceous aerosols emitted from different outdoor wood-fired boiler (OWB) technologies including two cord wood heaters, a pellet heater, and a multistage gasifier/combustor. The effect of fuel type [red oak wood (Quercus rubra), white pine wood (Pinus strobes), and red oak with supplementary refuse] on aerosol composition was examined using a classic boiler unit. Aerosol particle emissions were captured using established filter-based sampling methodology and subsequently analyzed using thermal-optical analysis and gas chromatography–mass spectrometry (GC-MS) techniques. GC-MS was coupled with a novel reduced-volume solvent extraction technique for semivolatile organic compound (SVOC) analysis. GC-MS identified 9% w/w of the aerosol mass emitted from the OWBs on average. The OWB aerosols comprised 1–5% w/w levoglucosan, an important molecular marker of cellulose pyrolysis. Organic acid and methoxyphenol SVOC classes showed the highest average concentrations in the OWB aerosol. Polycyclic aromatic hydrocarbons (PAHs) accounted for between 0.1 and 4% w/w of the aerosol mass; PAH emissions from pine wood combustion in the classic OWB were notably high. Each of the original 16 EPA priority PAHs was detected in the OWB PM emissions. Wood combustion in the OWB released significantly more PAH per unit mass of fuel burned than either domestic fireplace or woodstove appliances; although, changes in PAH enrichment (μg/kg aerosol) among domestic wood combustion aerosols was less certain. Of the OWBs tested, the pellet heater showed the lowest SVOC emissions on a mass of fuel burned basis. However, OWB technology did not always significantly influence the SVOC composition of the particle emissions

Correction to “Cookstove Emissions and Performance Evaluation Using a New ISO Protocol and Comparison of Results with Previous Test Protocols”

Correction to “Cookstove Emissions and Performance Evaluation Using a New ISO Protocol and Comparison of Results with Previous Test Protocols

Polycyclic Aromatic Hydrocarbons in Fine Particulate Matter Emitted from Burning Kerosene, Liquid Petroleum Gas, and Wood Fuels in Household Cookstoves

This study measures polycyclic aromatic hydrocarbon (PAH) compositions in particulate matter emissions from residential cookstoves. A variety of fuel and cookstove combinations are investigated, including: (i) liquid petroleum gas (LPG), (ii) kerosene in a wick stove, (iii) wood (10 and 30% moisture content on a wet basis) in a forced-draft fan stove, and (iv) wood in a natural-draft rocket cookstove. The wood burning in the natural-draft stove had the highest PAH emissions followed by the wood combustion in the forced-draft stove and kerosene burning. LPG combustion has the highest thermal efficiency (∼57%) and the lowest PAH emissions per unit fuel energy, resulting in the lowest PAH emissions per useful energy delivered (in the unit of megajoule delivered, MJ_d). Compared with the wood combustion emissions, LPG burning also emits a lower fraction of higher molecular weight PAHs. In rural regions where LPG and kerosene are unavailable or unaffordable, the forced-draft fan stove is expected to be an alternative because its benzo­[<i>a</i>]­pyrene (B­[<i>a</i>]­P) emission factor (5.17–8.24 μg B­[<i>a</i>]­P/MJ_d) and emission rate (0.522–0.583 μg B­[<i>a</i>]­P/min) are similar to those of kerosene burning (5.36 μg B­[<i>a</i>]­P/MJ_d and 0.452 μg B­[<i>a</i>]­P/min). Relatively large PAH emission variability for LPG suggests a need for additional future tests to identify the major factors influencing these combustion emissions. These future tests should also account for different LPG fuel formulations and stove burner types

Physical and Chemical Characterization of Residual Oil-Fired Power Plant Emissions

Although the toxicity of oil combustion emissions is a significant public health concern, few studies characterize the emissions from plant-scale utility boilers firing residual oil. This study remedies that deficiency by diluting, sampling, and monitoring stack emissions from a 432 gigajoules (GJ) front-fired fossil fuel steam generator burning residual oil. Over a 3-day test period, continuous CO₂, SO₂, and NO_<i>x</i> emissions monitoring confirms a steady fuel feed rate, high combustion efficiency (3.4 kg of CO₂/kg of fuel oil burned), and evidence of a nocturnal soot-blowing event. The utility boiler emits fine aerosol (PM_2.5) at a rate of 53 ± 2 μg/kJ (2 g/kg of oil burned). Vesicular coarse particles composed of C and S and spherical Al silicates with V and Ni inclusions are identified in a cyclone rinse using scanning electron microscopy and backscatter analysis. Ion chromatography results establish that the fine aerosol is predominantly sulfate (44% ± 0.2%, w/w) which is likely coordinated to transition metals. From thermal optical transmittance measurements, less than 1% (w/w) of the fine aerosol is surmised to be carbonaceous. Low emissions of particle-phase carbon and contaminants interfered with the gas chromatography−mass spectrometry (GC-MS) analysis of polcyclic aromatic hydrocarbons and certain other semivolatile organic compounds. However, trace levels of branched-, cyclic-, and <i>n</i>-alkanes and organic acids are observed in the particle emissions. Sterane and hopane molecules are below the picogram level GC-MS detection limits. Future research determining the individual organic species in the particles emitted from this source will require real-time single particle measurements. Finally, application of EPA methods TO-11 and TO-15 shows that the total volatile nonmethane organic gas emissions from the plant-scale boiler vary between 6 and 28 mg/kg of fuel oil burned; greater than 50% of this mass is ascribed to oxygenated matter

Carbonaceous Aerosols Emitted from Light-Duty Vehicles Operating on Gasoline and Ethanol Fuel Blends

This study examines the chemical properties of carbonaceous aerosols emitted from three light-duty gasoline vehicles (LDVs) operating on gasoline (e0) and ethanol-gasoline fuel blends (e10 and e85). Vehicle road load simulations were performed on a chassis dynamometer using the three-phase LA-92 unified driving cycle (UDC). Effects of LDV operating conditions and ambient temperature (−7 and 24 °C) on particle-phase semivolatile organic compounds (SVOCs) and organic and elemental carbon (OC and EC) emissions were investigated. SVOC concentrations and OC and EC fractions were determined with thermal extraction-gas chromatography–mass spectrometry (TE-GC-MS) and thermal-optical analysis (TOA), respectively. LDV aerosol emissions were predominantly carbonaceous, and EC/PM (w/w) decreased linearly with increasing fuel ethanol content. TE-GC-MS analysis accounted for up to 4% of the fine particle (PM_2.5) mass, showing the UDC phase-integrated sum of identified SVOC emissions ranging from 0.703 μg km^–1 to 18.8 μg km^–1. Generally, higher SVOC emissions were associated with low temperature (−7 °C) and engine ignition; mixed regression models suggest these emissions rate differences are significant. Use of e85 significantly reduced the emissions of lower molecular weight PAH. However, a reduction in higher molecular weight PAH entities in PM was not observed. Individual SVOC emissions from the Tier 2 LDVs and fuel technologies tested are substantially lower and distributed differently than those values populating the United States emissions inventories currently. Hence, this study is likely to influence future apportionment, climate, and air quality model predictions that rely on source combustion measurements of SVOCs in PM

Temperature and Driving Cycle Significantly Affect Carbonaceous Gas and Particle Matter Emissions from Diesel Trucks

The present study examines the effects of fuel [an ultralow sulfur diesel (ULSD) versus a 20% v/v soy-based biodiesel–80% v/v petroleum blend (B20)], temperature, load, vehicle, driving cycle, and active regeneration technology on gas- and particle-phase carbon emissions from light and medium heavy-duty diesel vehicles (L/MHDDV). The study is performed using chassis dynamometer facilities that support low-temperature operation (−6.7 °C versus 21.7 °C) and heavy loads up to 12 000 kg. Organic and elemental carbon (OC-EC) composition of aerosol particles is determined using a thermal-optical technique. Gas- and particle-phase semivolatile organic compound (SVOC) emissions collected using traditional filter and polyurethane foam sampling media are analyzed using advanced gas chromatograpy/mass spectrometry methods. Study-wide OC and EC emissions are 0.735 and 0.733 mg/km, on average. The emissions factors for diesel vehicles vary widely, and use of a catalyzed diesel particle filter (CDPF) device generally mutes the carbon particle emissions in the exhaust, which contains ∼90% w/w gas-phase matter. Interestingly, replacing ULSD with B20 did not significantly influence SVOC emissions, for which sums range from 0.030 to 9.4 mg/km for the L/MHDDVs. However, both low temperature and vehicle cold-starts significantly increase SVOCs in the exhaust. Real-time particle measurements indicate vehicle regeneration technology did influence emissions, although regeneration effects went unresolved using bulk chemistry techniques. A multistudy comparison of the toxic particle-phase polycyclic aromatic hydrocarbons (PAHs; molecular weight (MW) ≥ 252 amu) in diesel exhaust indicates emission factors that span up to 8 orders of magnitude over the past several decades. This study observes conditions under which PAH compounds with MW ≥ 252 amu appear in diesel particles downstream of the CDPF and can even reach low-end concentrations reported earlier for much larger HDDVs with poorly controlled exhaust streams. This rare observation suggests that analysis of PAHs in particles emitted from modern L/MHDDVs may be more complex than recognized previously

Effects of Cold Temperature and Ethanol Content on VOC Emissions from Light-Duty Gasoline Vehicles

Emissions of speciated volatile organic compounds (VOCs), including mobile source air toxics (MSATs), were measured in vehicle exhaust from three light-duty spark ignition vehicles operating on summer and winter grade gasoline (E0) and ethanol blended (E10 and E85) fuels. Vehicle testing was conducted using a three-phase LA92 driving cycle in a temperature-controlled chassis dynamometer at two ambient temperatures (−7 and 24 °C). The cold start driving phase and cold ambient temperature increased VOC and MSAT emissions up to several orders of magnitude compared to emissions during other vehicle operation phases and warm ambient temperature testing, respectively. As a result, calculated ozone formation potentials (OFPs) were 7 to 21 times greater for the cold starts during cold temperature tests than comparable warm temperature tests. The use of E85 fuel generally led to substantial reductions in hydrocarbons and increases in oxygenates such as ethanol and acetaldehyde compared to E0 and E10 fuels. However, at the same ambient temperature, the VOC emissions from the E0 and E10 fuels and OFPs from all fuels were not significantly different. Cold temperature effects on cold start MSAT emissions varied by individual MSAT compound, but were consistent over a range of modern spark ignition vehicles