Article pubs.acs.org/EF
Nonpolar Organic Compound Emission Rates for Light-Duty Diesel Engine Soybean and Waste Vegetable Oil Biodiesel Fuel Combustion John Kasumba* and Britt A. Holmén School of Engineering, The University of Vermont, 33 Colchester Ave., 103 Votey Hall, Burlington, Vermont 05405, United States S Supporting Information *
ABSTRACT: Very few studies report the detailed organic chemical composition of biodiesel exhaust PM despite reports that biodiesel exhaust PM leads to more adverse health effects than diesel exhaust PM. Here, we compare light-duty diesel engine exhaust particle-phase emission rates (ng/μg PM) of target nonpolar organic analytes19 n-alkanes, 16 priority PAHs, and 10 fatty acid methyl esters (FAMEs)during transient operation for 5 recycled waste vegetable oil (WVO; B00, B10, B20, B50, and B100) and 3 virgin soybean oil (soybean; B00, B20, and B100) biodiesel blends (where Bxx = volume % biodiesel). Biodiesel fuels were blended volumetrically from ultralow sulfur diesel (ULSD) and B100 from each feedstock. FAMEs emission rates were 3−7 times higher than n-alkanes for the common B20 blend, increasing to 60−100 times for B100. Both total n-alkanes and total FAMEs emission rate trends with Bxx were consistent with expected values based on fuel volume percent and similar ratios to ULSD were observed for both feedstocks. Total n-alkane emission rates decreased with increasing biodiesel content (B10 to B100) between 5−86% and 3−79% compared to ULSD, for WVO and soybean, respectively. Total FAMEs emission rates in WVO B100 exhaust PM were about 7, 3, and 2 times higher than WVO B10, B20, and B50 exhaust PM, respectively, with similar ratios for the soybean feedstock. In contrast, PAH emission rates, while statistically similar for both feedstocks, did not decrease as much as expected based on dilution of ULSD with B100 biodiesel, evidence that FAME or lubrication oil combustion account for PAH formation in higher biodiesel blends (greater than B20). Because emission rates of n-alkanes, PAHs, and FAMEs from recycled vegetable oil biodiesel were not statistically different from those for soybean biodiesel, based on nonpolar organic emissions alone, use of recycled waste cooking oil biodiesel is preferable to virgin vegetable oil biodiesel because of its dual use for food preparation prior to use as a renewable, low-carbon transportation fuel. Future studies should quantify how WVO biodiesel emissions are changed by use of emission control devices, such as DPF and SCR.
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INTRODUCTION Biodiesel, a fuel derived from renewable biological sources such as vegetable oils or animal fats,1 is typically comprised of fatty acid methyl esters (FAMEs) formed via transesterification, where triglycerides from vegetable oils or animal fats react with methanol in the presence of a base catalyst.2 Recent research has shown that, with the exception of NOx, most regulated exhaust emissions, such as hydrocarbons, carbon monoxide, and particulate matter (PM), are significantly reduced with biodiesel fuel substitution for petroleum diesel fuel.3−7 Further, in the limited studies that measured unregulated emissions/ species, carcinogenic and mutagenic polycyclic aromatic hydrocarbons (PAHs) have been lower with biodiesel.8−10 Very few prior studies have determined the detailed organic chemical speciation of exhaust from biodiesel combustion, yet such studies are critical to quantifying the full health and environmental effects associated with use of alternative biodiesel fuel, especially recycled waste vegetable oil (WVO) that may have different composition from virgin oil biodiesel. Diesel particulate matter (PM) is associated with adverse health effects including excess mortality, exacerbation of acute and chronic pulmonary disease symptoms, increased respiratory problems like asthma, and respiratory infections.11−16 It is possible that the chemical composition of PM (organic or inorganic) would better predict its association with human health effects compared to other PM characteristics such as mass and size.17 Recent laboratory studies have shown that © XXXX American Chemical Society
there is a relationship between PM organic compositional variability and PM-related toxicity, while epidemiologic studies demonstrate regional heterogeneity in PM-related health effects.13,18 In our recent study, oxidative stress biomarkers were 20−30% higher in animals exposed to soybean B20 biodiesel exhaust PM generated from a light-duty diesel engine than for ULSD exhaust PM from the same engine.19 The differential response was attributed to differences in the organic chemical composition (68% vs 46% polar fraction versus nonpolar fraction in B20 vs ULSD) of the diesel and biodiesel exhaust PM. Here, the detailed nonpolar organic chemical composition of diesel and biodiesel exhaust PM is reported for a series of biodiesel blends prepared from two feedstocks in order to establish a basis for improved understanding of the health effects of biodiesel exhaust PM emissions. A limited number of prior studies measured the speciated gas and particle emissions of PAHs, carbonyls, and hydrocarbons from diesel and different biodiesel feedstocks.7,10,20,21 Most prior studies, however, concentrated on a single class of compounds (PAHs, hydrocarbons, or carbonyls) and the biodiesel blends were often prepared with pre-ULSD petrodiesel that contain sulfur. Very few studies have comprehensively measured and compared emissions of a Received: June 30, 2016 Revised: September 23, 2016
A
DOI: 10.1021/acs.energyfuels.6b01582 Energy Fuels XXXX, XXX, XXX−XXX
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were determined gravimetrically for normalizing individual run emission rates of the target organic compounds. Exhaust particles were sampled on Teflon-coated Fiberfilm filters (FF, T60A20, diameter 47 mm, Pallflex Corp., Putman, CT) located at the end of a 2 m stainless steel transfer line to collect the total (gas +particle) emissions of the raw (undiluted) exhaust.26 Engine exhaust airflow through each filter was ∼16 L/min as determined by a rotameter. No backup filter was used to correct for volatile losses during sampling. The filter temperature during sampling was not directly measured for each test, but ranged from 21 to 45 °C for runs where it was measured. This temperature is below the 52 °C recommended by the US EPA for engine exhaust sampling and is therefore assumed to have a chemical composition that does not reflect reaction with the filter components, but was representative of the cooling and associated gas-particle partitioning behavior experienced when raw exhaust is diluted in ambient air. All FF filters were preweighed (after 24 h conditioning at 20−25 °C and 30−40% relative humidity) and postweighed with a Cahn C-33 microbalance (Thermo Scientific, Waltham, MA) with 1 μg sensitivity to determine the gravimetric mass of the sampled exhaust PM. To minimize reactions and volatile losses, all PM filter samples were stored at −80 °F after mass measurement until extraction for GC-MS analysis. Engine runs were performed in triplicate for each biodiesel blend tested (WVO sequence: B00, B10, B20, B50, B100; soybean sequence: B00, B20, B100) (Table S3). Four engine blank runs were performed during the sampling campaign by operating all sampling instruments the same way as during the emission test runs but with the engine off. The lubricating oil in the engine (Castrol, synthetic SAE 5W-40) was changed before the test sequence with each feedstock. The blends were tested in order B00, B10, B20, B50, and B100 for each feedstock, and a burnout procedure was performed before the soybean sequence in order to remove any residual emissions from the WVO test sequence. Chemicals. Dichloromethane, acetone, hexanes (OmniSolv, HRGC grade), methanol (B&J Purge and Trap GC Analysis), and acetonitrile (Carbonyl-free B&J) were all purchased from VWR International (West Chester, PA). Authentic standard mixtures of 13 even-numbered n-alkanes (C12−C36) and 10 FAMEs were from SigmaAldrich (Allentown, PA) and 16 EPA PAHs from Ultra Scientific (North Kingstown, RI). Table S4 lists the individual target analytes (nalkanes, PAHs, and FAMEs) and their concentrations in the commercial standards. Extraction and Analysis of Target Organic Chemical Compounds. Filters from triplicate WVO runs (B00 through B100) were used for chemical analysis, and because of time constraints, only duplicate soybean B00, B20, and B100 runs were extracted and analyzed for n-alkanes, PAHs, and FAMEs. Detailed information on filter extraction and GC-MS analytical parameters is provided in the SI and in Kasumba.27 During extraction, a 1/4-in. punch cut from each filter using a punch bore was placed in a 180 μL glass thermal desorption vial to which solvents were sequentially added, followed by sonication, to extract nonpolar and polar compounds. Extracts were analyzed on a 5890/ 5972 GC-MSD system (Agilent Technologies, Wilmington, DE) with a nonpolar column (Rxi-XLB 30m/0.25 mm/0.25 μm; Restek, Bellefonte, PA) for PAHs and n-alkanes and an Agilent 6890GC/ 5973 GC-MSD with a polar column (SLB-IL 100, 30m/0.25 mm/0.20 μm; Sigma-Aldrich) for FAMEs. The 5890 GC was equipped with a syringeless thermal desorption (TD) injector (Lavigne Laboratories, Storrs Mansfield, CT) and the 6890 GC with a liquid autosampler. Quality Control/Quality Assurance. Detection Limits. Method detection limits (MDLs) estimated according to EPA Method 556 (Equation S-1)28 shown in Table S5 indicate good detectability was achieved for n-alkanes C16−C26 and all FAMEs, with measured mass above MDL for all filter samples. For the PAHs, only phenanthrene, fluoranthene, and pyrene were detected at levels greater than MDL in all filter samples; other PAHs were not clearly detected and are not reported further. Detection of the majority of the analytes indicated that 1/4-in. punches could be used to determine target analyte concentrations on
variety of organic compound classes using the same biodiesel feedstock, engine, and engine operating conditions to help identify the biodiesel feedstock and blend that result in the least harmful PM emissions. Additionally, the detailed organic compound composition profile of the particles emitted from biodiesel combustion may provide valuable molecular marker information for receptor models/source apportionment.22,23 This study focused on the nonpolar organic chemical composition of raw exhaust PM (gas plus particle-phase emissions) from a light-duty diesel engine fueled with five biodiesel blends (B00, B10, B20, B50, and B100, where Bxx indicates the volume percent neat biodiesel in the fuel blend with ULSD) for waste vegetable oil (WVO) and virgin soybean oil biodiesel. B100 fuel from both feedstocks was prepared similarly and then mixed manually with ULSD by volume proportions prior to emissions testing. Statistical analyses were performed to compare nonpolar compound emission rates of target analytes in raw exhaust PM of the biodiesel blends to each other and to the emission rates of ULSD (B00). Attention was paid to quantifying the 16 EPA PAHs, 19 straight-chain nalkanes, and 10 FAMEs commonly found in soybean biodiesel fuel. The choice of these compounds was based on their known health effects, their contribution to environmental degradation due to their persistence, and commercial availability of their authentic analytical standards. FAMEs were chosen because of their abundance in the biodiesel fuel supply, despite the fact that their inhalation health effects and possible role in secondary air pollution are not well documented, while nalkanes were quantified because of their abundance in diesel fuel.
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MATERIALS AND METHODS
Emission Test Fuels. Ultralow sulfur diesel (ULSD) fuel was purchased commercially from Trono Fuels (Trono Oil and Gas Inc., Burlington, VT). Soybean vegetable oil was purchased from Catania Spagna Corp (Ayer, MA) and waste vegetable oil (WVO) was sourced from the University of Connecticut (Storrs, CT) dining halls where staff indicated that the cooking oil used was mainly canola oil. The 100% soybean and WVO biodiesel fuels were processed at the University of Connecticut’s Biofuels Laboratory, including preprocessing to remove free fatty acids, and treated with 2000 ppm (w/w) of Chemtura Naugalube 403 antioxidant.24 Neat biodiesel fuels were transported to the University of Vermont and stored at 13 °C under a N2 gas headspace to minimize oxidation before and after splash blending with ULSD. Fuel properties are shown in Table S1 (in the Supporting Information, SI) together with the ASTM D6751 biodiesel and the ASTM D975 diesel fuel standards. The soybean biodiesel fuel used in this study met all ASTM fuel specifications, while the cold soak filtration and the sodium and potassium tests for the WVO fuel did not conform to the ASTM specifications (Table S1). It is also important to note that two different lots of ULSD were used to prepare the WVO and soybean blends, both purchased from the same supplier (Trono Fuels). Fuel density was determined using an IROX Diesel Analyzer (Grabner Instruments, Austria), while other fuel properties were tested at the University of Connecticut’s Biofuels Laboratory. Emissions Test Procedure and Sampling. A Volkswagen 1.9L SDi naturally aspirated industrial diesel engine without exhaust gas recirculation or after-treatment devices and a Zelu SL/KLAM Eddy Current Dynamometer (Armfield Ltd., Model CM-12, Table S2) was operated using a combination of a 60 min transient cycle (12% average load) followed by three 10 min steady-state phases operating at different engine loads (5, 36, and 50% load, when the engine was fueled with ULSD). The transient drive cycle (Figure S1) was developed using real-world driving of a VW TDI Jetta in the Burlington, VT urban area.25 The exhaust flow rate for each run was measured on a second-by-second basis, and the PM mass emissions B
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Figure 1. Emission rates (ng/μg) of total n-alkanes (sum of emission rates of the detected target n-alkanes) in the raw exhaust PM of (a) WVO biodiesel blends (n = 3), and (b) soybean biodiesel blends (n = 2). Letters at top of the bars indicate groups that were statistically different for either the WVO or soybean biodiesel blends at α = 0.05. See Tables S9 and S10 for the p-values of the statistical tests for all blend pairs of WVO and soybean biodiesel exhaust PM, respectively. the entire filter, saving both time and extraction solvent, but also sacrificed the ability to detect some high molecular weight compounds that have been quantified in prior studies at very low concentrations.8−10 Engine and Laboratory Blanks. Engine and laboratory blank filters were extracted and analyzed the same way as emission test filters. No n-alkanes, PAHs, or FAMEs were detected in the engine blanks. Percent Recoveries and Reproducibility. Before extraction, each 1 /4-in. filter punch was spiked with nonpolar and polar recovery standards: 200 ng tetracosane-d50 and 100 ng of 2-fluoro-9-fluorenone (2F9F), respectively. The average recovery of tetracosane-d50 was 80 ± 23%, while that of 2F9F was 109 ± 58%. Good reproducibility (% RSD < 20%) of target analytes was assessed using multiple punches from one filter (see Kasumba27 for details) and RSD values greater than 30% observed for high volatility compounds (e.g., less than 14 carbon atoms) was probably caused by losses during extract blowdown. No corrections for percent recoveries were performed, and all data, including those with high variability, were used for data analysis. Average emission rates (ng/μg) of all target analytes for each biodiesel blend are reported in Tables S6−S8.
Data Analysis. Estimation of Individual Analyte Emission Rates. Emission rates, ER (mass of analyte per mass of PM sampled, ng/μg), were computed by dividing the total mass of analyte (ng) on the filter (Mi in eq 1) by the gravimetric mass of PM (μg) sampled during that particular run (Table S3). The mass of each target analyte in the entire 47 mm filter’s PM deposit, Mi, was computed from the GC-MS measured analyte mass (ng) on a punch, mi, and the filter deposit area (eq 1) and the assumption that there were 44 filter 1/4-in. punches in the filter deposit area (Np), given the 47 mm filter diameter and 2.5 mm O-ring edge width. The ER calculation assumes uniform filter deposit thickness.
ER =
Mi ; PM
M i = m i × Np
(1)
Mean and one standard deviation ERs of each analyte were reported based on duplicate (soybean) or triplicate (WVO) test filter analyses. Average emission rates of the different biodiesel blends were compared to those of ULSD (B00) by a percent difference calculation (eq 2). C
DOI: 10.1021/acs.energyfuels.6b01582 Energy Fuels XXXX, XXX, XXX−XXX
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and higher than those of WVO B50 and WVO B100 exhaust PM with p-values of 0.0134 and 0.0003, respectively. For the soybean feedstock, total n-alkane emission rates for soybean B20 and B100 decreased by 3.6% and 78.7%, respectively, compared to B00, but the soybean B00 and B20 differences were not statistically significant (Figure 1b, letter A). The 79% decrease in total n-alkane emission rate between soybean B00 and B100 exhaust PM was statistically significant (p-value =0.0306). Figure 2 shows the percent change in total n-alkanes emission as a function of biodiesel content for both feedstocks
%Difference (%Δ) Emission Rate for Bxx PM − Emission Rate for B00PM = × 100 Emission Rate for B00PM
(2) Analysis of Variance (ANOVA). ANOVA and two-way t tests (JMP Pro Version 11.2.0; SAS Institute Inc., Cary, NC) were used to statistically compare total analyte class emission rates (i.e., summed ER of all target analytes in each class) at a level of significance (α) = 0.05. Comparisons between individual blends of each feedstock as well as between feedstocks of a given blend ratio were considered to be statistically significant if the p-value was less than the level of significance (p-value 10% contribution to total FAMEs) in the biodiesel exhaust PM were methyl linoleate, methyl oleate, methyl palmitate, and methyl elaidate for both feedstocks, in no particular order of decreasing/ increasing concentration across all blends. With the exception of methyl elaidate, the most dominant FAMEs measured in biodiesel exhaust PM (methyl linoleate, methyl oleate, and methyl palmitate) were also the most dominant FAMEs in the B100 fuel samples (Table S13). Total FAME emission rates for the WVO B100 blend were approximately 7, 3, and 2 times greater than those for the WVO B10, B20, and B50 exhaust PM, respectively (Figure 5). Similarly, soybean B100 emission rates of the total speciated FAMEs were 3 times higher than those in soybean B20, and the differences were statistically significant (p-value = 0.0083). All of the differences in total FAME emission rates for the WVO biodiesel pairs were statistically significant except B10 and B20 (see Figure 5 and Table S11 for pairwise p-values). These data are consistent with one previous study where the total FAMEs in B100 tractor engine exhaust PM were 4 and 3 times greater than those of B50 for soybean and beef tallow feedstocks, respectively.22 Total FAME emission rates in each blend relative to B100 were very close to that expected based on biodiesel volume alone, but deviated more for the lower blends (Figure 6), possibly due to detection issues associated with analyzing the lower blends (B10 and B20). The increase in FAME emission rates with increasing biodiesel indicates significant release of unburned biodiesel fuel (e.g., fuel “by-pass”) in the exhaust that increased as the concentration of biodiesel in the fuel increased. The higher viscosity of biodiesel relative to petrodiesel may explain the observed fuel “by-pass” trend on engines with pump-line-nozzle fuel injection systems, as used here.25 More detailed analysis of the fuel together with exhaust FAMEs speciation are needed to understand the relative combustion F
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Figure 5. Emission rates (ng/μg) of total FAMEs (sum of emission rates of the speciated FAMEs) in the exhaust PM of (a) WVO biodiesel blends, and (b) soybean biodiesel blends. For WVO, n = 3; for soybean, n = 2.
aerosols that could affect particle properties such as hygroscopicity and ability to act as cloud condensation nuclei.48 Comparing FAME emissions between feedstocks, soybean B20 exhaust PM total FAME emission rates were 1.42 ± 0.06 times higher than those in WVO B20 exhaust PM, and the difference was statistically significant (p-value =0.0114). Soybean B100 exhaust PM FAMEs were 1.25 ± 0.09 times higher than those in WVO B100 exhaust PM, but the difference was not statistically significant (p-value =0.1499). MagaraGomez et al.22 reported soybean FAME emission rates that were higher than beef tallow by a factor of 1.34, similar to the ratio here for WVO and soybean. The reason for the difference in the emission rates of the total FAMEs in WVO B20 and soybean B20 exhaust PM could not be established, but could be due to slight differences in the sampling conditions, such as ambient temperature and RH experienced during the emissions tests of the two feedstocks, factors that affect particle formation and gas-to-particle partitioning of semivolatile organic compounds during sampling.22,49 Differences in FAME emission rates between the two feedstocks were not a result of differences in engine operation or fuel consumption for the two feedstocks because the average fuel consumption agreed within 3% between feedstocks (Table S3). Study Limitations and Implications for Biodiesel Use. Although this study was limited to analysis of raw exhaust PM, it is the first to report on light-duty diesel engine speciated
Figure 6. Total FAME emission rates ratio to B100 for the WVO and soybean biodiesel feedstocks. Each point represents the results for individual emission tests. Line shows expected ratio based on blend volume percent biodiesel and measured B100 total FAMEs emission rates.
efficiency of individual FAMEs and particle morphology as a function of engine operating conditions because emitted FAMEs contribute to the atmospheric burden of oxygenated G
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nonpolar organic chemical exhaust emissions from different ULSD/biodiesel blends for soybean and waste cooking oil biodiesel combustion. The light-duty diesel engine used in this study did not have a diesel particulate filter, diesel oxidation catalyst, or other emissions control technology (i.e., EGR, turbo, SCR). Installation of after-treatment devices to achieve the reductions needed to meet the current and future U.S emission standards50,51 is expected to have an effect on the emission of some compounds studied here. More detailed exhaust composition studies need to be performed with different biodiesel feedstock blends in order to evaluate: (i) how biodiesel fuel composition affects DPF and SCR durability and performance given recent reports documenting performance issues;52 (ii) how real-world use of after-treatment devices, such as DPFs, alters biodiesel PM exhaust composition53 and its associated effects on human health given recent reports suggesting that lower particle mass emissions alone do not necessarily reduce exhaust toxicity;9,54,55 and (iii) lubrication oil contribution to biodiesel exhaust composition. Also, it will be important to study exhaust particle organic composition by size fraction and quantify the more polar unregulated organic compounds in biodiesel exhaust PM that may be important to explain reactive oxygen species (ROS) formation. Based on our results, for the practical and most widely used biodiesel blends in diesel engines (B10 and B20), biodiesel use leads to 3−17% reductions in the emission of n-alkanes and 5− 38% PAHs, compared to ULSD. Complete elimination of PAH and n-alkane emissions, was not observed even with the 100% biodiesel fuels, indicating that potentially harmful PAHs and nalkanes are not only emitted as unburned fuel, but via combustion mechanisms in the engine, such as free radical interactions41 and lubricating oil combustion.40 If reduction of PAH and n-alkane emissions is of primary interest, biodiesel is a suitable substitute for commercial ULSD. Use of the neat fuels of either WVO or soybean biodiesel would be the most beneficial for PAH and n-alkane emissions, although impractical for cold weather climates56 and also because of the fact that modern diesel engines are not designed for pure biodiesel operation over extended periods of time. Given that the emission rates of both WVO and soybean biodiesel fuel blends were not statistically different, there appears to be no advantage of using one feedstock over the other in terms of the unregulated PAH, n-alkane, and FAME emissions investigated in this study. However, it would be more advantageous to use WVO biodiesel fuel derived from previously used soy or canola cooking oil than directly converting a foodstuff (virgin soybean oil) to fuel if all factors associated with production of both feedstocks, such as supply and costs, are constant.
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This project was funded in part by the US DOT through the UTC program at the University of Vermont Transportation Research Center (DTRT06-G-0018P). Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors wish to thank Tyler Feralio, Jim Dunshee, and Karen Sentoff for emissions testing, and Dr. Richard Parnas and Iman Norshad from the University of Connecticut for processing the WVO and soybean biodiesel fuels used in this study.
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REFERENCES
(1) Ma, F.; Hanna, M. A. Biodiesel production: a review1Journal Series #12109, Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska−Lincoln.1. Bioresour. Technol. 1999, 70 (1), 1−15. (2) Hoekman, S. K.; Broch, A.; Robbins, C.; Ceniceros, E.; Natarajan, M. Review of biodiesel composition, properties, and specifications. Renewable Sustainable Energy Rev. 2012, 16 (1), 143−169. (3) McCormick, R. L.; Graboski, M. S.; Alleman, T. L.; Herring, A. M.; Tyson, K. S. Impact of Biodiesel Source Material and Chemical Structure on Emissions of Criteria Pollutants from a Heavy-Duty Engine. Environ. Sci. Technol. 2001, 35 (9), 1742−1747. (4) US EPA. A comprehensive analysis of biodiesel impacts on exhaust emissions Draft Technical Report; 420-NaN-02−001; National Service Center for Environmental Publications: Cincinnati, OH, 2002. (5) Krahl, J.; Munack, A.; Schröder, O.; Stein, H.; Bunger, J. Influence of biodiesel and different petrodiesel fuels on exhaust emissions and health effects. In The Biodiesel Handbook; Knothe, G., Van Gerpen, J., Krahl, J., eds.; AOCS Press: Champaign, IL, 2005; pp 175−182. (6) Knothe, G.; Sharp, C. A.; Ryan, T. W. Exhaust Emissions of Biodiesel, Petrodiesel, Neat Methyl Esters, and Alkanes in a New Technology Engine †. Energy Fuels 2006, 20 (1), 403−408. (7) Bakeas, E.; Karavalakis, G.; Stournas, S. Biodiesel emissions profile in modern diesel vehicles. Part 1: Effect of biodiesel origin on the criteria emissions. Sci. Total Environ. 2011, 409 (9), 1670−1676. (8) Lin, Y.-C.; Lee, W.-J.; Hou, H.-C. PAH emissions and energy efficiency of palm-biodiesel blends fueled on diesel generator. Atmos. Environ. 2006, 40 (21), 3930−3940. (9) Chien, S.-M.; Huang, Y.-J.; Chuang, S.-C.; Yang, H.-H. Effects of Biodiesel Blending on Particulate and Polycyclic Aromatic Hydrocarbon Emissions in Nano/Ultrafine/Fine/Coarse Ranges from Diesel Engine. Aerosol Air Qual. Res. 2009, 9 (1), 18−31. (10) Karavalakis, G.; Boutsika, V.; Stournas, S.; Bakeas, E. Biodiesel emissions profile in modern diesel vehicles. Part 2: Effect of biodiesel origin on carbonyl, PAH, nitro-PAH and oxy-PAH emissions. Sci. Total Environ. 2011, 409 (4), 738−747.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.energyfuels.6b01582.
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NOMENCLATURE ASTM= American Society for Testing and Materials Bxx= Biodiesel blend volume % ER= Emission rate FAMEs= Fatty acid methyl esters GC= Gas chromatography MS= Mass spectrometry PAH= Polycyclic aromatic hydrocarbons PM= Particulate matter RH= Relative humidity soybean= Soybean oil biodiesel ULSD= Ultralow sulfur diesel fuel WVO= Waste vegetable oil
Detailed methods and tables of individual compound emission rates results and statistical analyses (PDF)
AUTHOR INFORMATION
Corresponding Author
*
[email protected]. H
DOI: 10.1021/acs.energyfuels.6b01582 Energy Fuels XXXX, XXX, XXX−XXX
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DOI: 10.1021/acs.energyfuels.6b01582 Energy Fuels XXXX, XXX, XXX−XXX
