Ethanol, Isobutanol, and Biohydrocarbons as Gasoline Components

Ethanol, Isobutanol, and Biohydrocarbons as Gasoline Components in Relation to .... The low-oxygen fuel matrix was targeted to comply with the Europea...
0 downloads 0 Views 2MB Size
Download PDF
Article pubs.acs.org/est

Ethanol, Isobutanol, and Biohydrocarbons as Gasoline Components in Relation to Gaseous Emissions and Particulate Matter Paï vi T. Aakko-Saksa,*,† Leena Rantanen-Kolehmainen,‡ and Eija Skytta†̈ †

VTT Technical Research Centre of Finland, P. O. Box 1000, FI-02044 VTT, Finland Neste Oil, 06101 Porvoo, Finland

‡

S Supporting Information *

ABSTRACT: The exhaust emissions of three cars using different biofuels were explored at a temperature of −7 °C. The biofuels studied contained both low- and highconcentration ethanol blends, isobutanol, and biohydrocarbons. A multipoint fuel injection car (MPFI), direct-injection spark-ignition car (DISI), and flex-fuel car (FFV) represented three different spark-ignition-car technologies. At −7 °C, substantial emissions were observed for the three cars, and differences were found among ethanol, isobutanol, and biohydrocarbons as fuel components. For example, E85 resulted in high acetaldehyde, formaldehyde, ethanol, ethene, and acetylene emissions when compared to E30 or lower ethanol concentrations. Isobutanol-containing fuel showed elevated butyraldehyde, methacrolein, and isobutanol emissions. The highest particulate matter (PM) emissions, associated polyaromatic hydrocarbon (PAH) and indirect mutagenicity emissions were detected with the DISI car. Oxygenated fuels reduced PM emissions and associated priority PAH emissions in the DISI car. PM and PAH emissions from the MPFI and FFV cars were generally low. A combination of 10% ethanol and biohydrocarbon components did not change emissions significantly when compared to ethanol-only-containing E10 gasoline. Therefore, a combination of ethanol or isobutanol with biohydrocarbon components offers an option to reach high gasoline bioenergy content for E10-compatible cars.

■

INTRODUCTION Transport biofuels have been introduced to cope with challenges of climate change and energy security. In addition, the effect of new fuels on air quality is an important consideration. This covers both primary and secondary emissions and their environmental and health impacts. Ethanol is the most widely used transport biofuel today. Future options considered for the gasoline pool include biobutanol and biohydrocarbons. Many exhaust species are limited by legislation. In addition, a number of other exhaust species are known to be harmful to human health and the environment. The U.S. Environmental Protection Agency (EPA) has defined key mobile-source air toxics (MSATs), comprising substances such as benzene, 1,3butadiene, formaldehyde, acetaldehyde, acrolein, polycyclic organic matter (POM), naphthalene, diesel exhaust and gasoline particulate matter (PM).1 From these key MSATs, the contribution from mobile sources is greatest for 1,3butadiene, benzene, formaldehyde, acetaldehyde, and acrolein.2 Benzene and formaldehyde are classified as human carcinogens. The lifetime of 1,3-butadiene is short, but it is highly reactive and may form formaldehyde, acetaldehyde, and acrolein. Acetaldehyde is a carcinogen in rodents, but the data on its carcinogenicity in humans are inadequate.2 Acrolein is highly © 2014 American Chemical Society

irritating, and long-term inhalation results in chronic inflammation. POM is found in the exhaust gas phase, particle phase, or both. POM contains a mixture of compounds, for example benzo(a)pyrene, which is classified as a human carcinogen. In addition, the emission of ammonia is associated with harmful effects on health and vegetation, and it can also form ammonium aerosols that affect climate, and visibility;3 finally, nitrous oxide is a strong greenhouse gas. The Ames test provides one of the most widely used shortterm mutagenicity assays and is often applied as a preliminary screening tool for chemicals with potential genotoxic activity. A positive result from the Ames test provides an indication of genotoxic potential that must be confirmed by some other method capable of more accurately predicting the risk of carcinogenicity in mammals. In addition to its use with single chemicals, the Ames test has been used for a long time to assess the mutagenicity of a wide variety of complex samples.4,5 The Ames test in mutagenicity testing is discussed in the Supporting Information. Received: Revised: Accepted: Published: 10489

March 21, 2014 July 25, 2014 July 30, 2014 July 30, 2014 dx.doi.org/10.1021/es501381h | Environ. Sci. Technol. 2014, 48, 10489−10496

Environmental Science & Technology

Article

Table 1. Test Fuelsa

Exhaust emissions from cars diminish with tightening emissions legislation. However, it has been revealed that reallife emissions are higher than those expected based on typeapproval tests, which are carried out at normal temperature with certain driving cycles.6 Spark-ignition cars equipped with a three-way catalyst (TWC) are especially sensitive to test temperature.7−9 Ambient temperature is an important parameter when exhaust emissions are being investigated. The normal temperature of emission tests is typically +23 °C, whereas the cold temperature is −7 °C in the European emission regulation for cars. Increasing the ethanol content of gasoline generally increases acetaldehyde emissions, whereas PM emissions tend to decrease.10,11 Increases in acetaldehyde emissions have been observed mainly during cold-start and aggressive driving, not during stabilized driving.11 High-concentration ethanol blends (E85) increase ethanol, acetaldehyde, formaldehyde, and methane emissions, when compared with low-oxygen-content gasoline, whereas the CO, HC, NOx, 1,3-butadiene, benzene, and toluene emissions tend to decrease. E85 fuel produces lower PM and PAH emissions than low-oxygen-content gasoline at normal temperature, but its PM and PAH emissions can increase at low temperatures.3,7,12,13,37 Limited data are available on the exhaust emissions from butanol-containing gasoline. CO and HC were reduced or not changed significantly when isobutanol or n-butanol blends were compared with gasoline, whereas contradictory results have been reported for NOx emissions.14,16−19 One study using cars reported that many emissions were higher with n-butanol than with isobutanol.15 Increased formaldehyde, acetaldehyde propene, 1,3-butadiene, and acetylene emissions have been observed with n-butanol and isobutanol, whereas aromatic hydrocarbon emissions have reduced.20,36 Gasoline-range biohydrocarbons resemble conventional gasoline, and they are compatible with conventional cars and infrastructure. However, the product quality ranges from higharomatic and high-octane qualities to paraffinic low-octane hydrocarbon mixtures depending on the feedstock and production technology used. Biohydrocarbons for gasoline can be obtained for example by methanol-to-gasoline (MTG) processes, aqueous-phase catalytic conversion, the Fischer− Tropsch process, integrated refinery, or co-processing.21−23 Larsen et al. studied emissions by using gasoline containing 70% Fischer−Tropsch (FT) components in a direct-injection gasoline car.24 The aromatic content of this gasoline was high (32%), and it does not represent Fischer−Tropsch gasoline in general. HC, CO, and PM emissions were lower, but NOx and PAH emissions were higher for the FT-containing fuel than for gasoline. In this study, exhaust emissions with biofuels containing lowand high-concentration ethanol blends, isobutanol, and biohydrocarbons were explored with three different sparkignition gasoline car technologies at a temperature of −7 °C. The combination of ethanol or isobutanol with renewable hydrocarbon components could offer an option to reach gasoline with a high bioenergy content that is compatible with traditional gasoline-fueled cars.

fossil E10 E10 + R iBu E30 E85

bioenergy (E%)

volumetric share of biocomponent (%, v/v)

oxygen (%, m/m)

0 7 22 14 23 78

0 10 26 17 31 85

0.1 3.7 4.0 3.8 11.3 29.8

a

E = ethanol, iB = isobutanol, R = renewable hydrocarbons. Number indicates volume of biocomponent.

quality. The Neste Oil renewable gasoline component represented liquid biohydrocarbons. The batch used was a C5−C9 paraffinic component (oxygen-, aromatic-, and sulfurfree; density, 672 g/L; dry vapor pressure equivalent (DVPE), 45 kPa), which is a side product of producing renewable diesel from vegetable oil and animal fat by using Neste Oil’s NExBTL hydroprocessing technology. Fuels were match-blended using fossil gasoline refinery components and gasoline biocomponents. The low-oxygen fuel matrix was targeted to comply with the European EN228 gasoline specification and was tested using both conventional cars and the FFV car. Fuel properties, e.g., aromatic content, density, vapor pressure, sulfur, and octane number were kept as constant as possible. Since the fuels with an oxygen content higher than approximately 4% (m/m) are not necessarily compatible with conventional spark-ignited cars, high-oxygencontaining fuels were tested only with the FFV car. Oxygen-free fossil hydrocarbon gasoline was used as a reference fuel. The bioenergy content of fuels was from 7 to 78 E% on an energy basis. A high bioenergy level of 22 E% compatible with traditional cars was achieved by combining ethanol and nonoxygenated biohydrocarbon components. Fuels were labeled using the biocomponent abbreviation and the corresponding blending share of the component. For example, E10 fuel contains 10% (v/v) ethanol (E). The abbreviations iBu and R were used for the isobutanol and renewable gasoline components, respectively. Cars. Experimental work was carried out with three cars: a multipoint fuel injection car (MPFI), a direct-injection sparkignition car (DISI), and a flex-fuel car (FFV). The MPFI and DISI cars were model year 2010, whereas the FFV car was model year 2006. The MPFI and DISI cars represent conventional cars, which are not necessarily compatible with fuels containing more than approximately 4% (m/m) oxygen. An FFV car tolerates high-oxygen-containing gasoline, e.g., up to 85% ethanol. The engine control unit of the FFV adjusts the air-to-fuel ratio depending on the oxygen content of the exhaust gases.26 The characteristics of the cars are shown in the Supporting Information. Test Procedure. Tests were conducted on a chassis dynamometer in a climatic test cell at −7 °C using a driving cycle according to the Directive 70/220/EEC and its amendments. The driving cycle was 11.007 km in total. The FFV car was conditioned according to the manufacturer’s instructions, and the adaptation of the car to new fuel was monitored. For gaseous emissions, 2−4 replicate tests were typically carried out. For the PAH and Ames tests, two replicate tests were carried out for the DISI car, whereas the MPI and FFV cars generated too low a PM mass for replicate tests. The number of replicate tests is shown in the Supporting

■

EXPERIMENTAL SECTION Fuels. Five fuels are presented in this work (Table 1). More detailed fuel properties are presented in the Supporting Information. The present study is a submatrix of 14 fuels studied earlier.15,25 In this study, the E85 fuel was market-grade 10490

dx.doi.org/10.1021/es501381h | Environ. Sci. Technol. 2014, 48, 10489−10496

Environmental Science & Technology

Article

Figure 1. CO and HC (top, left) and NOx (top, right) emissions together with individual C1−C8 hydrocarbons (bottom) from the MPFI, DISI, and FFV cars over the European test cycle at −7 °C. Standard deviations of hydrocarbons are presented as error bars, if replicate tests are available.

Information. Error bars in the figures represent the standard deviation calculated from the replicate tests. For fuel comparisons, average change percentages and 95% confidence intervals according to the two-sample t test are presented in the Supporting Information. Gaseous Emissions. Equipment used in the measurement of the CO, HC, and NO x emissions consisted of a dynamometer (Froude Consine 1.0 m, DC, 100 kW), constant volume sampler (AVL CVS i60 LD, Venturi-type), and triple bench for gaseous regulated emissions (Pierburg AMA 2000). The true oxygen contents and densities of the fuels were used to calculate the results. A density of 0.619 kg/dm3 was used in the calculation of the HC emissions. The response of oxygenates on a flame ionization detector was not taken into account.27,15 Aldehydes were collected from the CVS diluted exhaust gas using dinitrophenylhydrazine cartridges and analyzed using high-performance liquid chromatography (HPLC) technology (Agilent 1260, UV detector, Nova-Pak C18 column). The aldehydes analyzed were formaldehyde, acetaldehyde, acrolein, propionaldehyde, crotonaldehyde, methacrolein, butyraldehyde, benzaldehyde, valeraldehyde, mtolualdehyde, and hexanal. Individual hydrocarbons analyzed using a gas chromatograph (HP 5890 Series II, AL2O3, KCl/ PLOT column) were methane, ethane, ethene, propane, propene, acetylene, isobutene, 1,3-butadiene, benzene, toluene,

ethylbenzene, and m-, p-, and o-xylenes. A number of compounds, among others ethanol, ammonia, and nitrous oxide, were measured online using Fourier transformation infrared (FTIR) equipment (Gasmet Cr-2000). Particulate Matter. PM was collected with a high-capacity collection system.8 This includes a dilution tunnel (i.d. = 265 mm), a sample probe (i.d. = 80 mm), two filter holders in parallel (i.d. = 142 mm), a blower (Siemens ELMO-G), a flow meter (Bronkhorst F-106C1-HD-V-12), and a controller (Stafsjö MV-E-80-P-TY-AC100-PN10). The sample flow in these measurements was 700−850 L/min. The filter type was Fluoropore 3.0 μm FSLW. The microbalance was a Sartorius SE2-F. Soxhlet Extraction. Soxhlet extraction with dichloromethane was conducted for the filter samples. Several filters were combined for each extraction batch, and an equivalent number of filters was used for the control sample. Filters were protected from light during and after the Soxhlet treatment. The Soxhlet apparatus was cleaned by solvent extraction (6 h). An internal standard was added, and samples were Soxhletextracted for 16 h. The evaporated concentrates were divided for the PAH analyses and Ames tests. For the Ames test, the solvent was replaced by dimethyl sulfoxide (DMSO). Filters were dried in decanters and weighed for determination of the soluble organic fraction (SOF). 10491

dx.doi.org/10.1021/es501381h | Environ. Sci. Technol. 2014, 48, 10489−10496

Environmental Science & Technology

Article

Polyaromatic Hydrocarbons. A total of 30 individual PAHs were analyzed from the Soxhlet-extracted PM samples using GC/SIM-MS following purification of the extract by liquid chromatography. An EPA 610 PAH mixture from Supelco and PAH-MIX 63 from Ehrensdorf were used to check the calibration standard, which was made from pure solid substances of each PAH compound determined. The detection limit was 0.1 μg of component/sample, which represents approximately 0.04 μg/km for the MPFI car and 0.08 μg/km for the DISI and FFV cars over the European test. Focus was placed on seven PAHs defined in a list of mobile-source air toxics by the U.S. EPA (2007): benzo(a)anthracene (BaA, group 2B), chrysene (Chr, group 2B), benzo(b)fluoranthene (BbF, group 2B), benzo(k)fluoranthene (BbF, group 2B), benzo[a]pyrene (BaP, group 1), 7,12-dimethylbenz[a]anthracene, and indeno(1,2,3-cd)pyrene (IP, group 2B). Ames Test. Mutagenicity of the extracted PM samples was assessed by the Ames test using two tester strains, Salmonella typhimurium TA98 and TA98NR. The method applied (VTT4352-91) is based on the original reference method of Maron and Ames28 and the recommendations of the OECD.29 In the preliminary tests, the mutagenic properties of PM extracts were precharacterized by using TA98 both with and without metabolic activation (±S9 mix) and the nitro-reductasedeficient strain TA98NR (−S9 mix). In the final assessment the samples were tested only for indirect mutagenicity using strain TA98 with metabolic activation (+S9). The indirect mutagenicity of PM extracts was assessed at five dose levels corresponding to PM masses of 0.1−0.8 mg/plate. The S9 homogenate used for metabolic activation was prepared from male Wistar rat livers induced with phenobarbital and βnaphthoflavone. The concentration of liver homogenate in the S9 mix was 4% (v/v). The tests were carried out only once, typically using three replicate plates for each dose level. The positive control for indirect mutagenicity was 2-aminoanthracene (0.5 μg/plate). DMSO (100 μL/plate) was used as the solvent control. To be classified as mutagenic, the sample must cause a dose-related, more than 2-fold, increase in the number of revertants compared with the solvent control. The mutagenic dose response of each sample was calculated by linear regression analysis. The magnitude of mutagenic activity expressed as revertants per milligram of of sample is the slope (b) within the linear part of the regression line (y = bx + a). Results were presented as krev/(mg of PM) and as krev/km.

emissions with E85 fuel. However, these emissions might be lower for a modern FFV car operating on E85 at −7 °C. Oxygenated fuel resulted in an increase in NOx emission for the MPFI and FSI cars, whereas a reduction in NOx emission was observed with increasing fuel oxygen content for the FFV car. Average changes in emissions between fuels and p-values are presented in the Supporting Information Benzene, toluene, ethylbenzene, and xylenes (BTEX) dominated the C1−C8 hydrocarbons (Figure 1). Methane, ethene, acetylene, and BTEX emissions were particularly high for the FFV car when using the E85 fuel. Changes in C1−C8 hydrocarbon emissions were smaller for other fuels. The emission level of 1,3-butadiene was very low with all cars tested, with a maximum of 3.3 mg/km. Acetaldehyde and ethanol emissions increased with increasing ethanol content of the fuel, whereas the addition of an isobutanol component led to elevated formaldehyde, acrolein, butyraldehyde, methacrolein, propionaldehyde, and isobutanol emissions. The sum of 11 aldehydes analyzed was higher for butanol-containing fuels than for ethanol-containing fuels at similar fuel oxygen contents, particularly for the MPFI and FFV cars. Average changes in emissions between fuels and p-values are presented in the Supporting Information, as well as a figure on speciated aldehyde emissions. Aldehyde and alcohol emissions did not increase linearly with the oxygen content of the fuel (Figure 2). At −7 °C, E85 fuel showed particularly

Figure 2. Correlation between the oxygen content of test fuels and aldehyde and alcohol emissions from the MPFI, DISI, and FFV cars over the European test cycle at −7 °C.

■

RESULTS Gaseous Emissions. CO was the dominating tailpipe exhaust emission from the cars tested (Figure 1). CO emission was below 4 g/km and HC emission below 0.6 g/km for fuels other than E85, which showed higher emissions (CO, 5.6 g/ km; HC, 2.4 g/km). NOx emission was below 0.12 g/km, and NO2 below 0.011 g/km for all three cars. These results at −7 °C were in-line with the results reported by Dardiotis et al.9 Compared to results at standard test temperature, CO and HC emissions were high at −7 °C with all cars tested, whereas NOx emissions were relatively low. The three cars behaved somewhat differently toward fuel changes. Adjustments to cars may cause different responses to fuel properties, such as density, oxygen content, octane numbers, and volatility. The use of low-concentration oxygenated fuels reduced CO and HC emissions in most cases for the MPFI and DISI cars, whereas no significant change was observed for the FFV car. Elevated CO and HC emissions were seen with E30 fuel and high

high acetaldehyde emissions: when changing from E30 to E85 fuel, acetaldehyde emission increased by 7.6 times and ethanol emission by 27 times. E85 fuel also increased formaldehyde emission. E85 had a strong impact on the correlation between fuel oxygen content and carbonyl emissions. The Pearson’s correlation factors between fuel oxygen content and aldehyde/ alcohol emissions were 0.93/0.89 when all fuels were taken into account, whereas correlation was 0.83/0.75 when E85 was excluded. A combination of biohydrocarbons and ethanol did not produce consistent changes in gaseous emissions when compared with the ethanol-only-containing E10 fuel. Ammonia emissions were notable for the three cars tested (up to 39 mg/km, FFV car), whereas nitrous oxide emissions were low. Ammonia and nitrous oxide emissions are formed in the reactions of the three-way catalyst. In addition, low-sulfur fuels may enhance the tendency of TWC to form ammonia.30 10492

dx.doi.org/10.1021/es501381h | Environ. Sci. Technol. 2014, 48, 10489−10496

Environmental Science & Technology

Article

Figure 3. PM emissions (top) and priority PAH emissions (bottom) from the MPFI, DISI, and FFV cars over the European test cycle at −7 °C. Standard deviations are presented as error bars for PM emission and the sum of priority PAH emissions, if replicate tests are available.

emissions from the DISI car were substantially higher than those from the MPFI and FFV cars in mass concentration terms (mass per particulate mass) and particularly high in terms of mass emission per kilometer. Oxygenated fuels reduced PAH emissions in the DISI car, which was evident as mass concentration (micrograms of PAH per milligram particulate mass; p-values 0.01−0.03) and in mass emissions (micrograms of PAH per kilometer; p-values 0.02−0.11). In most cases, no clear differences were observed in PAH emissions between fuels with the MPFI and FFV cars. However, E85 fuel resulted in higher PAH emissions than other fuels tested with the FFV car. For the MPFI car, isobutanol-containing fuel seemed to slightly elevate PAH emission (μg/km). The predominant priority PAHs observed were benz(a) anthracene, benzo(b)fluoranthene, and benzo(a)pyrene. For the three cars tested representing different gasoline car technologies, the compound profiles for the priority PAHs were quite similar. For the DISI car, benzo(a)pyrene emission was 10−30 μg/km depending on the fuel, whereas values for the MPFI car were below 2.5 μg/km and for the FFV car 1.5− 10 μg/km. In mass concentration terms (micrograms of PAH per milligram of particulate mass), benzo(a)pyrene emission was 1.0−1.3 μg/mg for the DISI car and 0.4−1 μg/mg for the MPFI and FFV cars. The PM extracts from the three cars tested exhibited strong, indirect mutagenicity of the frameshift-type, most likely caused

Gaseous emissions with a warmed-up engine were only a fraction of the emissions produced throughout the cold-start European driving cycle. CO, HC, acetaldehyde, 1,3-butadiene, and benzene emissions were only approximately 10% and NOx emission 18% with a warmed-up engine in the extra-urban driving cycle (EUDC) part of the European driving cycle. Formaldehyde emissions, however, were relatively high even in the EUDC part: 45−80% of the European test. PM, PAH, and Mutagenicity. Particulate matter mass emissions from the MPFI and FFV cars were low, in most cases below 4.5 mg/km, and changes in PM emissions seemed not to be fuel-related (Figure 3). In contrast, the DISI car showed high PM emissions (10−20 mg/km), and oxygenated fuels seemed to reduce PM emission though a significant change was seen only for E10 fuel (p-value 0.03). The PM emission levels of these cars are in-line with the results from Dardiotis et al., who reported PM emissions below 4.7 mg/km (three cars) and 7 mg/km (one car) at −7 °C over the European test cycle.9 The SOF of PM was typically close to 2 mg/km for all cars. PM emission from the DISI car contained a large inorganic fraction, leading to a low share of SOF (12.4 ± 4.6%) compared to that of the MPFI and FFV cars (46 ± 10% and 53 ± 11%). After-treatment particle filter devices would reduce PM emissions from the DISI cars. When tested at −7 °C, the amount of PM-associated PAH emissions was high for all three cars (Figure 3). Priority PAH 10493

dx.doi.org/10.1021/es501381h | Environ. Sci. Technol. 2014, 48, 10489−10496

Environmental Science & Technology

Article

by PAHs. The highest mutagenicity in TA98 was induced by the extract obtained from the DISI car. The sample from the DISI car showed a substantially higher indirect than direct mutagenicity (−S9, 4.3 krev/km; +S9, 32 krev/km), whereas no indication of the presence of nitro-PAH-type mutagenicity could be demonstrated (TA98NR; −S9, 4.8 krev/km). As the PM extracts from the DISI car exhibited extremely high indirect mutagenicity even at very low PM dose levels, mutagenicity emissions per kilometer were exceptionally high (20−100 krev/ km). The PM extracts of the FFV car showed slightly lower but still strong indirect mutagenicity (2−25 krev/km), whereas substantially lower (1−10 krev/km) indirect mutagenicity was associated with the PM emissions of the MPFI car. In earlier studies, the PM-associated emissions generated by MPFI gasoline cars and EEV diesel buses have been reported to show direct mutagenicity against the strain TA98. Typically the mutagenicity has been below 5 krev/km, i.e., clearly less than that resulting from the PM emissions of the old diesel cars, especially at −7 °C (44−112 krev/km).8,31−33 The Pearson’s correlation factors between PAHs and PMassociated indirect mutagenicity were weak or not significant. The strongest correlation was observed for PM-associated benzo(a)pyrene emission and the Ames test result for perkilometer units (Figure 4). In this case, PM-associated

Figure 5. Indirect mutagenic response (TA98+S9 mix) induced by PM emission extracts from the direct-injection engine (DISI) car using different fuels.

Figure 5). In addition, some samples were inhibitory to the test organism at higher dose levels. As for the calculation of dose response values by linear regression analysis, only the results obtained within a noninhibitory/not acutely toxic PM range (mg/plate) could be included, so a comparison of the mutagenicity responses of different samples can only be conducted at a semiquantitative level. On the basis of the current results, it can therefore only be concluded that the fuel compositions studied may have a minor effect on the mutagenicity of the PM-associated emissions generated. However, a much more significant role seems to be played by the engine technology applied.

■

DISCUSSION Ethanol is the dominant biofuel today in the transport sector, and other options are being considered, such as biobutanol and biohydrocarbons. At the same time, new engine technologies are being introduced, for example, direct-injection gasoline engines and flexible fuel vehicles. Changes in fuel chemistry and engine technology may lead to new characteristics of exhaust gases. These effects are emphasized during the start of trips and in heavy driving conditions,11 in general when the TWC does not perform optimally. Starting the car at low ambient temperature is a particularly critical condition. Standard emission tests are carried out at +22 °C. However, average real-life temperatures are often lower; for example, the average annual temperature in Europe was 10.6 °C in 2012.35 In addition, average driving distances are only 10−13 km per trip in Europe.34 In this study, emissions from the spark-ignition gasoline cars proved to be elevated at low test temperature. The impact of fuels on exhaust emissions was substantial in many cases, but in this respect there were differences between cars representing different engine technologies. Direct-injection engine technology (DISI car) showed elevated PM emissions and associated PAH and mutagenicity emissions compared to the indirectinjection engine technology (MPFI and FFV cars). The PM emissions and associated PAH emissions of the DISI car could be reduced by oxygenated fuels. This applies to ethanol and isobutanol as well as to a combination of ethanol and biohydrocarbons. In the FFV car, the use of high ethanol concentrations at low temperatures deserves further research.

Figure 4. Correlation between Ames mutagenicity and benzo(a)pyrene emissions from the MPFI, DISI, and FFV cars over the European test cycle at −7 °C.

benzo(a)pyrene explained approximately 70% of the Ames test result, but only approximately 39% of the concentrationbased result (per milligram). The weak contribution of the analyzed PAHs to the indirect-acting mutagenicity indicates that more detailed analysis is needed to analyze different types of compounds in the particulate matter.4 The observed slight correlation indicates differences among the cars, whereas no correlation is seen among the fuels for each car. Some differences in the mutagenic activity of the PM extracts seemed to be attributable to the fuel compositions used. The DISI car using isobutanol-containing fuel produced lessmutagenic PM extracts than the DISI car using the E10 + R fuel. Moreover, the PM extracts from the FFV car seemed to exhibit higher mutagenicity with the E85 fuel than with the other fuels. However, samples were more mutagenic than expected, and only a few dose levels tested were in the reliably measurable area (below 1000 revertant colonies per plate; 10494

dx.doi.org/10.1021/es501381h | Environ. Sci. Technol. 2014, 48, 10489−10496

Environmental Science & Technology

Article

vehicles fuelled by ethanol-blended gasoline. Appl. Energy 2013, 102, 44−54. (4) Yang, X.-Y.; Igarashi, K.; Tang, N.; Lin, J.-M.; Wang, W.; Kameda, T.; Toriba, A.; Hayakawa, K. Indirect- and direct-acting mutagenicity of diesel, coal and wood burning-derived particulates and contribution of polycyclic aromatic hydrocarbons and nitropolycyclic aromatic hydrocarbons. Mutat. Res., Genet. Toxicol. Environ. Mutagen. 2010, 695, 29−34. (5) Health assessment document for diesel engine exhaust., EPA/600/890/057F; United States Environmental Protection Agency (U.S. EPA): Washington, DC, USA, 2002 (May). (6) Air quality in Europe2012 report; European Environment Agency EEA: Copenhagen, Denmark, 2012. (7) Nylund, N.-O.; Aakko, P. Particle emissions at moderate and cold temperatures using different fuels, SAE Technical Paper 2003-01-3285, Society of Automotive Engineers: Warrendale, PA, USA, 2003. (8) Kokko, J.; Rantanen, L.; Pentikainen, J.; Honkanen, T.; Aakko, P.; Lappi, M. Reduced particulate emissions with reformulated gasoline, SAE Technical Paper 2000-01-2017; Society of Automotive Engineers: Warrendale, PA, USA, 2000. (9) Dardiotis, C., Martini, G., Manfredi, G. Revision of low temperature emission standards for petrol vehicles. JRC scientific and policy reports, Report EUR 256672 EN; European Union Joint Research Centre: Patten, The Netherlands, 2012. (10) Larsen, U.; Johansen, T.; Schramm, J. Ethanol as a fuel for road transportation, Annex XXXV report, IEA advanced motor fuels agreement; Advanced Motor Fuels: Bern, Switzerland, 2009 (11) Graham, L.; Belisle, S.; Baas, C.-L. Emissions from light duty gasoline vehicles operating on low blend ethanol gasoline and E85. Atmos. Environ. 2008, 42, 4498−4516. (12) Westerholm, R., Ahlvik, P., Karlsson, H. L. An exhaust characterization study based on regulated and unregulated tailpipe and evaporative emissions from bi-fuel and flexi-fuel light-duty passenger cars fuelled by petrol (E5), bioethanol (E70, E85) and biogas tested at ambient temperatures of +22 and 7 °C, Final report to the Swedish Road Administration, March 2008. (13) Karlsson, H.; Gåste, J.; Åsman, P. Regulated and non-regulated emissions from Euro 4 alternative fuel vehicles, SAE technical paper 200801-1770; Society of Automotive Engineers.: Society of Automotive Engineers: Warrendale, PA, USA, 2008. (14) 1-Butanol as a gasoline blending bio-component. BP presentation, 2006. (15) Aakko-Saksa, P.; Rantanen-Kolehmainen, L.; Koponen, P.; Engman, A.; Kihlman, J. Biogasoline optionsPossibilities for achieving high bio-share and compatibility with conventional cars. SAE Int. J. Fuels Lubr. 2011, 4, 298−317. (16) Wallner, T.; Miers, A.; McConnell, S. A comparison of ethanol and butanol as oxygenates using a direct-injection, spark-ignition engine. J. Eng. Gas Turbines Power 2009, 131, No. 032802. (17) Yang, J.; Yang, X.; Liu, J.; Han, Z.; Zhong, Z., Dyno test investigations of gasoline engine fueled with butanol-gasoline blends, SAE Technical paper 2009-01-1891; Society of Automotive Engineers: Warrendale, PA, USA, 2009. (18) Cooney, C.; Wallner, T.; McConnel, S.; Gillen, J.; Abell, C.; Miers, S. Effects of blending gasoline with ethanol and butanol on engine efficiency and emissions using a direct-injection, spark-ignition engine, technical paper ICES2009-76155; American Society of Mechanical Engineers (ASME): New York, 2009. (19) Thewes, M.; Müther, M.; Brassat, A.; Pischinger, S.; Sehr, A. Analysis of the effect of bio-fuels on the combustion in a downsized DI SI engine, SAE technical paper 2011-01-1991; Society of Automotive Engineers: Warrendale, PA, USA, 2011. (20) Wallner, T.; Frazee, R. Study of regulated and non-regulated emissions from com-bustion of gasoline, alcohol fuels and their blends in a DI-SI engine, SAE technical paper 2010-01-1571; Society of Automotive Engineers: Warrendale, PA, USA, 2010. (21) Blommel, P.; Cortright, R. Production of conventional liquid fuels from sugars, Virent’s white paper, 2008.

The results on engine technologies are not conclusive due to the limited number of cars tested. Spark-ignition gasoline car emissions are concentrated close to living areas and parking places, where cold-start emissions play a significant role. In particular, PAH and mutagenicity emissions from gasoline cars at moderate and cold temperatures warrant further attention. In-depth research on health and environmental perspectives, including the secondary atmospheric reactions, should be considered in parallel with climate change issues when new fuels and technologies are considered.

■

ASSOCIATED CONTENT

S Supporting Information *

Text giving additional details for methods and results, tables listing test fuels, characteristics of cars, various emissions results, and a figure showing aldehyde emissions. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*Phone: +358 40 720 7846; fax: +358 20 722 7048; e-mail: paivi.aakko-saksa@vtt.fi. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We acknowledge participants in the project and personnel at VTT and Neste Oil. The financial support of the Ministry of Employment and the Economy (TEM) in Finland is acknowledged.

■

NOMENCLATURE CO carbon monoxide CO2 carbon dioxide DISI direct-injection spark ignition DVPE dry vapor pressure equivalent E% bioenergy content as percentage EEV enhanced environmentally friendly vehicle FFV flexible-fuel (flex-fuel) vehicle HC hydrocarbons MPFI multipoint fuel injection MSAT mobile-source air toxics NExBTL Neste Oil hydroprocessing technology and product NOx nitrogen oxides PAH polyaromatic hydrocarbons PM particulate matter POM polycyclic organic matter SOF soluble organic fraction TWC three-way catalyst

■

REFERENCES

(1) Control of hazardous air pollutants from mobile sources. Final rule, 40 CFR Parts 59, 80, 85 and 86; United States Environmental Protection Agency (U.S. EPA): Washington, DC, USA, 2007 (February). (2) Mobile-source air toxics: A critical review of the literature on exposure and health effects, Special Report 16; HEI, Health Effects Institute: Boston, MA, USA, 2007. (3) Clairotte, M.; Adam, T. W.; Zardini, A. A.; Manfredi, U.; Martini, G.; Krasenbrink, A.; Vicet, A.; Tournie, E.; Astorga, C. Effects of low temperature on the cold start gaseous emissions from light duty 10495

dx.doi.org/10.1021/es501381h | Environ. Sci. Technol. 2014, 48, 10489−10496

Environmental Science & Technology

Article

(22) Holmgren, J.; Mariangeli, R.; Marker, T.; McCall, M.; Petri, J.; Czernik, S.; Elliot, D.; Shonnard, D. Opportunities of biorenewables. Hydrocarbon Eng. 2007, http://www.energyglobal.com/magazines/ latestissue/hydrocarbon-engineering.aspx. (23) Huber, G.; Iborra, S.; Corma, A. Synthesis of transportation fuels from biomass: Chemistry, catalyst and engineering. Chem. Rev. 2006, 106, 4044−4098. (24) Larsen, U.; Lundorf, P.; Ivarsson, A.; Schramm, J. Emissions from diesel and gasoline vehicles fuelled by Fischer−Tropsch fuels and similar fuels, SAE Technical Paper 2007-01-4008; Society of Automotive Engineers: Warrendale, PA, USA, 2007. (25) Aakko-Saksa, P.; Koponen, P.; Kihlman, J.; Reinikainen, M.; Skyttä, E.; Rantanen-Kolehmainen, L.; Engman, A. Biogasoline options for conventional spark-ignition cars, VTT working papers 187; VTT: Espoo, Finland, 2011. (26) West, B.; López, A.; Theiss, T.; Graves, R.; Storey, J.; Lewis, S. Fuel economy and emissions of the ethanol-optimized Saab 9-5 biopower, SAE technical paper 2007-01-3994; Society of Automotive Engineers: Warrendale, PA, USA, 2007. (27) Sandström-Dahl, C.; Erlandsson, L.; Gåsste, J.; Lindgren, M. Measurement methodologies for hydrocarbons, ethanol and aldehyde emissions from ethanol fuelled vehicles, SAE technical paper 2010-011557; Society of Automotive Engineers: Warrendale, PA, USA, 2010. (28) Maron, M. D.; Ames, B. N. Revised methods for the Salmonella mutagenicity test. Mutat. Res. 1983, 113, 173−215. (29) Genetic toxicology: Salmonella typhimurium, reverse mutation assay. OECD guidelines for testing of chemicals, Test No. 471; OECD: Paris, 1997. (30) Mejia-Centeno, I.; Martínez-Hernández, A.; Fuentes, G. Effect of low-sulfur fuels upon NH3 and N2O emission during operation of commercial three-way catalytic converters. Top. Catal. 2007, 42−43, 381−385. (31) Pentikäinen, J.; Rantanen, L.; Aakko, P. The effect of heavy olefins and ethanol on gasoline emissions, SAE technical paper 2004-01-2003; Society of Automotive Engineers: Warrendale, PA, USA, 2004. (32) Murtonen, T.; Aakko-Saksa, P. Alternative fuels with heavy-duty engines and vehicles: VTT’s contribution, VTT working papers 128; VTT: Espoo, Finland, 2009. (33) Rantanen, L.; Juva, A.; Niemi, A.; Mikkonen, S.; Aakko, P.; Lappi, M. Effect of reformulated diesel fuel on unregulated emissions of light duty vehicles, SAE technical paper 961970; Society of Automotive Engineers: Warrendale, PA, USA, 1996. (34) De La Fuente, L. Passenger mobility in Europe. Statistics in focus: Transport, 87/2007, Catalog No. KS-SF-07-087-EN-N; Eurostat: Luxembourg, 2007. (35) Climate indicator bulletin CIB, EURO4M project, Jan. 25, 2013. http://cib.knmi.nl/mediawiki/index.php/European_Temperature. (36) Ratcliff, M. A.; Luecke, J.; Williams, A.; Christensen, E.; Yanowitz, J.; Reek, A.; McCormick, R. L. Impact of higher alcohols blended in gasoline on light-duty vehicle exhaust emissions. Environ. Sci. Technol. 2013, 47, 13865−13872. (37) Yanowitz, J.; Knoll, K.; Kemper, J.; Luecke, J.; McCormick, R. L. Impact of adaptation on flex-fuel vehicle emissions when fueled with E40. Environ. Sci. Technol. 2013, 47, 2990−2997.

10496

dx.doi.org/10.1021/es501381h | Environ. Sci. Technol. 2014, 48, 10489−10496