Roger Westerholm

Chemical and physical characterization of emissions from birch wood combustion in a wood stove.

The purpose of this study was to characterize the emissions of a large number of chemical compounds emitted from birch wood combustion in a wood stove. Birch wood is widely used as fuel in Swedish household appliances. The fuel load was held constant during six experiments. Particles < 2.5 mum diameter were collected and the size distribution of the particles was measured. The results were compared to the size distribution in road traffic emissions. It could be seen that the number distribution differed between the sources. In traffic exhaust, the number of particles maximized at 20 nm, while the number distribution from wood burning ranged from 20 to 300 nm. The ratio K/Ca on particles was found. to be significantly different in wood burning compared to road dust, range 30-330 for the former and 0.8+/-0.15 for the latter. The source profile of common elements emitted from wood-burning differed from that found on particles at a street-level site or in long-distance transported particles. The ratio toluene/benzene in this study was found to be in the range 0.2-0.7, which is much lower than the ratio 3.6+/-0.5 in traffic exhaust emissions. Formaldehyde and acetone were the most abundant compounds among the volatile ketones and aldehydes. The emission factor varied between 180-710mg/kg wood for formaldehyde and 5-1300mg/kg wood for acetone. Of the organic acids analyzed (3,4,5)-trimethoxy benzoic acid was the most abundant compound. Of the PAHs reported, fluorene, phenanthrene, anthracene, fluoranthene and pyrene contribute to more than 70% of the mass of PAH. Of the elements analyzed, K and Si were the most abundant elements, having emission factors of 27 and 9mg/kg wood, respectively. Although fluoranthene has a toxic equivalence factor of 5% of benzo(a)pyrene (B(a)P), it can be seen that the toxic potency of fluoranthene in wood burning emissions is of the same size as B(a)P. This indicates that the relative carcinogenic potency contribution of fluoranthene in wood smoke would be about 40% of B(a)P

State of the art of multi-fuel reformers for fuel cell vehicles : problem identification and research needs

This review is focused on discussions about multi-fuel reformer technology for fuel cell vehicles where techniques for onboard hydrogen generation and gas clean-up processes, as well as fuel considerations and emissions are included. Our conclusion is that the potential for developing a highly efficient, durable and reliable reformer system for automotive applications is considerably higher if dedicated fuel reformers are used instead of applications where all types of fuels ranging from natural gas to heavy diesel fuels can be used. The authors propose that petroleum-derived fuels should be designed for potential use in mobile fuel cell applications. The present literature review together with site visit discussions has led to the conclusion that there are relatively low emissions from fuel cell engines compared to internal combustion engines. However, the major research work on reformers/fuel cells have been performed during steady-state operation. Emissions during start-up, shutdown and transient operation are basically unknown and must be investigated in more detail.

Effect of fuel polycyclic aromatic hydrocarbon content on the emissions of polycyclic aromatic hydrocarbons and other mutagenic substances from a gasoline-fueled automobile

Exhaust emissions from a fuel-injected, Otto engine equipped car driven according to the US Federal Test Procedure (FTP-73) were characterized chemically and by mutagenicity tests. Four fuel qualities of different polycyclic aromatic hydrocarbon (PAH) content were used. Emission variables investigated were regulated pollutants (CO, unburned hydrocarbons, NO/sub x/), particle emissions, emission of particle and gas phase associated polycyclic aromatic hydrocarbons, aldehyde emissions, emissions of benzene, toluene, ethene, and propene, and mutagenicity in particle and gas phases. The amount of formed PAH emitted in the exhaust is approximately constant. In fuels with low PAH contents a large proportion of emitted PAH was formed. Most of the cyclopenta(cd)pyrene and benzo(b and k) fluoranthene, greater than or equal to 80% and greater than or equal to 70%, respectively, is formed in the combustion process. All the exhaust samples, except one, in both the particulate phase and the gas phase, gave significant mutagenic effects on Salmonella typhimurium tester strains TA98 and TA100 with or without a metabolizing system (S9). Generally, the gas phase gave a higher effect compared to the particulate phase. The best correlation between emitted PAH and mutagenicity was found for the particulate phase and TA100+S9.

A multivariate statistical analysis of fuel-related polycyclic aromatic hydrocarbon emissions from heavy-duty diesel vehicles.

The fuel-dependent emissions of polycyclic aromatic hydrocarbons (PAH) were studied in diluted exhaust from two heavy-duty diesel vehicles during transient driving conditions. Principal component analysis (PCA) was used to investigate the relationship between fuel parameters and PAH contents in fuels. The PCA model shows that certain fuel parameters are related to PAH contents in diesel fuels. Linear regression analysis, PCA, and partial least-squares regression to latent structures (PLS) were used to study the correlation of PAH in fuels and PAH in exhaust emissions. The statistical methods used support the fact that there is a relationship between PAH contents in the diesel fuel and PAH contents emitted in the exhaust emissions. The PLS model resulted in correlation coefficients of r = 0.97 and r = 0.93 for vehicles 1 and 2, respectively. The PAH emission emitted in the exhaust consists of uncombusted through fuel input PAH and PAH formed in the combustion process. This investigation shows that it is possible to reduce PAH emissions in exhaust originating from uncombusted fuel PAH by using diesel fuels with PAH contents less than 4 mg/L. 22 refs., 5 figs., 2 tabs.

Cold start emissions at +22, −7 and −20°C ambient temperatures from a three-way catalyst (TWC) car: regulated and unregulated exhaust components

A project initiated by the Swedish Environmental Protection Agency (SEPA) concerning cold start driving conditions is partially reported in the present paper. A three-way catalyst car was run in accordance with the European driving cycle (EDC) at 22°C, −7°C and −20°C ambient temperatures. The diluted exhaust was analyzed for: Carbon monoxide (CO), unburned fuel hydrocarbons (HC), oxides of nitrogen (NOx), particulates, light aromatics, alkenes, green house gases, aldehydes and polycyclic aromatic hydrocarbons (PAH) in particles and in the gaseous phase. As expected, the emission factors of both regulated and unregulated exhaust components increased at lower ambient temperatures. However, the emissions did not increase uniformly. The mutagenic/carcinogenic compound benz[a]pyrene for example, increased more than 100 times while CO and HC only increased 5–20 times at the lowest ambient temperature studied.

Antioxidant airway responses following experimental exposure to wood smoke in man

BackgroundBiomass combustion contributes to the production of ambient particulate matter (PM) in rural environments as well as urban settings, but relatively little is known about the health effects of these emissions. The aim of this study was therefore to characterize airway responses in humans exposed to wood smoke PM under controlled conditions. Nineteen healthy volunteers were exposed to both wood smoke, at a particulate matter (PM2.5) concentration of 224 ± 22 μg/m3, and filtered air for three hours with intermittent exercise. The wood smoke was generated employing an experimental set-up with an adjustable wood pellet boiler system under incomplete combustion. Symptoms, lung function, and exhaled NO were measured over exposures, with bronchoscopy performed 24 h post-exposure for characterisation of airway inflammatory and antioxidant responses in airway lavages.ResultsGlutathione (GSH) concentrations were enhanced in bronchoalveolar lavage (BAL) after wood smoke exposure vs. air (p = 0.025), together with an increase in upper airway symptoms. Neither lung function, exhaled NO nor systemic nor airway inflammatory parameters in BAL and bronchial mucosal biopsies were significantly affected.ConclusionsExposure of healthy subjects to wood smoke, derived from an experimental wood pellet boiler operating under incomplete combustion conditions with PM emissions dominated by organic matter, caused an increase in mucosal symptoms and GSH in the alveolar respiratory tract lining fluids but no acute airway inflammatory responses. We contend that this response reflects a mobilisation of GSH to the air-lung interface, consistent with a protective adaptation to the investigated wood smoke exposure.

Regulated and unregulated exhaust emissions from two three-way catalyst equipped gasoline fuelled vehicles

This investigation presents emission factors of both regulated (CO, HC, NOx and particulate) and unregulated pollutants (aldehydes, monocyclic aromatic compounds and polycyclic aromatic compounds) measured under three different driving conditions, i.e. cold transient, stabilised and hot transient. These three driving conditions were simulated using the US FTP-75 driving cycle. Two three-way catalyst equipped light duty passenger cars were investigated. As expected, a higher emission of both regulated and unregulated pollutants was observed in the cold start phase of the driving cycle.

A multivariate statistical analysis of chemical composition and physical characteristics of ten diesel fuels

Ten different diesel fuels were tested for 26 physical and 45 chemical parameters. Principal components analysis (PCA) was used for statistical analysis of the physical and chemical data separately and combined. Physically, these and similar fuels may be described in a few general terms, such as viscosity, boiling residue, cetane number and density. With three PCs, 88% of the variation in physical terms was accounted for. Only one fuel remained poorly described by the model. The most descriptive chemical components include 1-methylphenanthrene as representative of a major fraction of the polycyclic aromatic hydrocarbons (PAH). With three PCs, all fuels were well accounted for, with 80% of the variation in chemical parameters explained. Although PCA does not provide a means of deriving causal relations, it may be used to find patterns of intercorrelated variables. With both chemical and physical parameters included in a final PCA, relations between chemical contents and physical characteristics were observed for e.g. PAH/olefins/naphthenes and viscosity.

Wood smoke particles from different combustion phases induce similar pro-inflammatory effects in a co-culture of monocyte and pneumocyte cell lines

BackgroundExposure to particulate matter (PM) has been linked to several adverse cardiopulmonary effects, probably via biological mechanisms involving inflammation. The pro-inflammatory potential of PM depends on the particles’ physical and chemical characteristics, which again depend on the emitting source. Wood combustion is a major source of ambient air pollution in Northern countries during the winter season. The overall aim of this study was therefore to investigate cellular responses to wood smoke particles (WSPs) collected from different phases of the combustion cycle, and from combustion at different temperatures.ResultsWSPs from different phases of the combustion cycle induced very similar effects on pro-inflammatory mediator release, cytotoxicity and cell number, whereas WSPs from medium-temperature combustion were more cytotoxic than WSPs from high-temperature incomplete combustion. Furthermore, comparisons of effects induced by native WSPs with the corresponding organic extracts and washed particles revealed that the organic fraction was the most important determinant for the WSP-induced effects. However, the responses induced by the organic fraction could generally not be linked to the content of the measured polycyclic aromatic hydrocarbons (PAHs), suggesting that also other organic compounds were involved.ConclusionThe toxicity of WSPs seems to a large extent to be determined by stove type and combustion conditions, rather than the phase of the combustion cycle. Notably, this toxicity seems to strongly depend on the organic fraction, and it is probably associated with organic components other than the commonly measured unsubstituted PAHs.

Particulate PAH Emissions from Residential Biomass Combustion: Time-Resolved Analysis with Aerosol Mass Spectrometry

Time-resolved emissions of particulate polycyclic aromatic hydrocarbons (PAHs) and total organic particulate matter (OA) from a wood log stove and an adjusted pellet stove were investigated with high-resolution time-of-flight aerosol mass spectrometry (AMS). The highest OA emissions were found during the addition of log wood on glowing embers, that is, slow burning pyrolysis conditions. These emissions contained about 1% PAHs (of OA). The highest PAH emissions were found during fast burning under hot air starved combustion conditions, in both stoves. In the latter case, PAHs contributed up to 40% of OA, likely due to thermal degradation of other condensable species. The distribution of PAHs was also shifted toward larger molecules in these emissions. AMS signals attributed to PAHs were found at molecular weights up to 600 Da. The vacuum aerodynamic size distribution was found to be bimodal with a smaller mode (Dva ∼ 200 nm) dominating under hot air starved combustion and a larger sized mode dominating under slow burning pyrolysis (Dva ∼ 600 nm). Simultaneous reduction of PAHs, OA and total particulate matter from residential biomass combustion may prove to be a challenge for environmental legislation efforts as these classes of emissions are elevated at different combustion conditions.