The first study evaluates the effect of two low blend ethanol gasolines (E10, E20) ontailpipe and evaporative emissions from three multi-port fuel injection vehicles and one gasoline direct injection vehicle attwo different test temperatures. The second study evaluates the differences in tailpipe emissions and fuel consumptions ofpaired flexible fuel and conventional gasoline vehicles operating on California RFG Phase 2 and/or E85 fuels at 20 1C.
19
Atmospheric Environment 42 (2008) 4498–4516 Emissions from light duty gasoline vehicles operating on low blend ethanol gasoline and E85 Lisa A. Graham , Sheri L. Belisle, Cara-Lynn Baas 1 Emissions Research and Measurement Division, Environmental Science and Technology Centre, Environment Canada, 335 River Road, Ottawa, Ontario, Canada K1A 0H3 Received 19 September 2007; received in revised form 24 January 2008; accepted 29 January 2008 Abstract The results of two recent vehicle emission studies are described in this paper, along with a statistical analysis of the changes in tailpipe emissions due to the use of ethanol that includes the results from these two studies in combination with results from other literature reports. The first study evaluates the effect of two low blend ethanol gasolines (E10, E20) on tailpipe and evaporative emissions from three multi-port fuel injection vehicles and one gasoline direct injection vehicle at two different test temperatures. The second study evaluates the differences in tailpipe emissions and fuel consumptions of paired flexible fuel and conventional gasoline vehicles operating on California RFG Phase 2 and/or E85 fuels at 20 1C. The vehicles were tested over the four-phase FTP or UDDS and US06 driving cycles. Tailpipe emissions were characterized for criteria pollutants (CO, NO X , NMHC, NMOG), greenhouse gases (CO 2 , CH 4 ,N 2 O), and a suite of unregulated emissions including important air toxics (benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein), and ozone reactivity. In the low blend ethanol study, evaporative emissions were quantified and characterized for NMHC. While contradicting, results can be seen among the various literature reports and with these two new studies, the statistical analyses of the aggregated data offers much clearer pictures of the changes in tailpipe emissions that may be expected using either low blend ethanol gasoline (E10) or E85. The results of the statistical analysis suggest that the use of E10 results in statistically significant decreases in CO emissions (16%); statistically significant increases in emissions of NMHC (9%), NMOG (14%), acetaldehyde (108%), 1,3-butadiene (16%), and benzene (15%); and no statistically significant changes in NO X , CO 2 , CH 4 , N 2 O or formaldehyde emissions. The statistical analysis suggests that the use of E85 results in statistically significant decreases in emissions of NO X (45%), NMHC (48%), 1,3-butadiene (77%), and benzene (76%); statistically significant increases in emissions of formaldehyde (73%) and acetaldehyde (2540%), and no statistically significant change in CO, CO 2 , and NMOG emissions. Crown Copyright r 2008 Published by Elsevier Ltd. All rights reserved. Keywords: Ethanol–gasoline blends; Mobile source air toxics; Greenhouse gas emissions; Evaporative emissions 1. Introduction Today, the motivations for blending ethanol with gasoline are different in Canada and the USA. However, these motivations have evolved over the last 15 years from a common starting point: reducing the negative impacts on local and regional ARTICLE IN PRESS www.elsevier.com/locate/atmosenv 1352-2310/$ - see front matter Crown Copyright r 2008 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2008.01.061 Corresponding author. Tel.: +1 613 990 1270; fax: +1 613 952 1006. E-mail address: [email protected] (L.A. Graham). 1 Present address: Industry Canada, 50 Victoria St., Gatineau, Quebec, Canada, K1A 0C9.
Transcript
ARTICLE IN PRESS
1352-2310/$ - se
doi:10.1016/j.at
�Correspondfax: +1613 952
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Quebec, Canad
Atmospheric Environment 42 (2008) 4498–4516
www.elsevier.com/locate/atmosenv
Emissions from light duty gasoline vehicles operating onlow blend ethanol gasoline and E85
Lisa A. Graham�, Sheri L. Belisle, Cara-Lynn Baas1
Emissions Research and Measurement Division, Environmental Science and Technology Centre, Environment Canada,
335 River Road, Ottawa, Ontario, Canada K1A 0H3
Received 19 September 2007; received in revised form 24 January 2008; accepted 29 January 2008
Abstract
The results of two recent vehicle emission studies are described in this paper, along with a statistical analysis of the
changes in tailpipe emissions due to the use of ethanol that includes the results from these two studies in combination with
results from other literature reports. The first study evaluates the effect of two low blend ethanol gasolines (E10, E20) on
tailpipe and evaporative emissions from three multi-port fuel injection vehicles and one gasoline direct injection vehicle at
two different test temperatures. The second study evaluates the differences in tailpipe emissions and fuel consumptions of
paired flexible fuel and conventional gasoline vehicles operating on California RFG Phase 2 and/or E85 fuels at 20 1C. The
vehicles were tested over the four-phase FTP or UDDS and US06 driving cycles. Tailpipe emissions were characterized for
criteria pollutants (CO, NOX, NMHC, NMOG), greenhouse gases (CO2, CH4, N2O), and a suite of unregulated emissions
including important air toxics (benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein), and ozone reactivity. In the
low blend ethanol study, evaporative emissions were quantified and characterized for NMHC. While contradicting, results
can be seen among the various literature reports and with these two new studies, the statistical analyses of the aggregated
data offers much clearer pictures of the changes in tailpipe emissions that may be expected using either low blend ethanol
gasoline (E10) or E85. The results of the statistical analysis suggest that the use of E10 results in statistically significant
decreases in CO emissions (�16%); statistically significant increases in emissions of NMHC (9%), NMOG (14%),
acetaldehyde (108%), 1,3-butadiene (16%), and benzene (15%); and no statistically significant changes in NOX, CO2, CH4,
N2O or formaldehyde emissions. The statistical analysis suggests that the use of E85 results in statistically significant
decreases in emissions of NOX (�45%), NMHC (�48%), 1,3-butadiene (�77%), and benzene (�76%); statistically
significant increases in emissions of formaldehyde (73%) and acetaldehyde (2540%), and no statistically significant change
in CO, CO2, and NMOG emissions.
Crown Copyright r 2008 Published by Elsevier Ltd. All rights reserved.
Keywords: Ethanol–gasoline blends; Mobile source air toxics; Greenhouse gas emissions; Evaporative emissions
e front matter Crown Copyright r 2008 Published by
Today, the motivations for blending ethanol withgasoline are different in Canada and the USA.However, these motivations have evolved over thelast 15 years from a common starting point:reducing the negative impacts on local and regional
ARTICLE IN PRESSL.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–4516 4499
air quality that arise from gasoline-powered vehicleemissions, specifically ground level ozone, toxic airpollutants, and carbon monoxide. In 1992, the USClean Air Act implemented a wintertime oxyge-nated fuels program for cities with elevated ambientconcentrations of CO during the cold months. Thisprogram required 2.7% by weight of oxygen ingasoline and the oxygenate of choice for thisprogram was ethanol (US EPA, 2007a). In Canada,similar fuels were available, but were not mandatedas in the USA. In 1995, the US Federal Reformu-lated Gasoline (RFG) regulations were introduced.RFG is required by the US Clean Air Act in citieswith the worst smog pollution and other cities withsmog problems may choose to use RFG. RFG iscurrently used in 17 states and the District ofColumbia and about 30% of gasoline sold inthe USA is reformulated (US EPA, 2007b). TheRFG regulations established emissions performancerequirements for gasoline and required an oxygencontent of at least 2% by weight. This regulationalso served to enhance energy security by extendingthe gasoline supply with the use of domesticallyproduced and renewable energy sources. Californiahas RFG regulations that are more stringent thanthe federal requirements and are intended to achievesimilar goals. The oxygenate of choice in federalRFG was MTBE (methyl-t-butyl ether) (US EPA,2007b) which accounted up to 87% of the oxygenateuse. Ethanol was also used in RFG. Given theenvironmental concerns that have emerged concern-ing the detection of MTBE in groundwater anddrinking water in the United States (McCarthy andTiemann, 2001), many states have banned the use ofMTBE in RFG (US EPA, 2007c). In February2006, the federal RFG regulations were amendedto remove the requirement for oxygenate content(US EPA, 2007d). With the US Energy Policy Actof 2005, energy security (reducing the dependenceon foreign suppliers) has become the primarymotivator for the use of ethanol in gasoline, as itcan be produced domestically (US EPA, 2007f).
Canada has regulations controlling the level ofsulphur and benzene in gasoline (EnvironmentCanada, 2007a). In December 2006, the governmentannounced that it intends to mandate a 5% byvolume renewable fuel content based on the gaso-line pool, starting in 2010 (Environment Canada,2007b). The primary environmental motivation forthe use of renewable fuels in gasoline in Canada isto achieve a reduction in lifecycle greenhouse gasemissions. Economic motivators for Canadian
farmers and rural communities are equally asimportant as the Canadian bio-economy grows.
Low blend ethanol gasoline results in changes insome vehicle tailpipe emissions. While individualstudies often showed contradictory results, gener-ally, emissions of CO are reduced, effects on NOX,NMHC and some air toxic emissions are generallyminimal, while emissions of formaldehyde andacetaldehyde are increased compared to traditionalgasoline.
Higher ethanol blends, up to 85% ethanol ingasoline, have been available on a limited basis inboth Canada and the USA for many years. Sincethese fuels cannot be used in conventional vehiclesfor several reasons, specially equipped flexible-fuelvehicles are required (US EPA, 2007e). Interest inthese higher blends has increased very recently withthe new US Energy Policy Act of 2005, and theRenewable Fuel Standard which took effect inSeptember 2007. This program is designed tosignificantly increase the volume of renewable fuelthat is blended into gasoline with the primarymotivation of energy security. Renewable fuels alsooffer lifecycle greenhouse gas emission reductionopportunities.
As seen with low blend ethanol studies, individualE85 studies show conflicting results, but generally,E85 results in emission reductions for NOX, 1,3-butadiene, benzene, and NMHC, emission increasesfor formaldehyde and acetaldehyde and littlechange (sometimes positive, sometimes negative) inCO and NMOG emissions.
This paper begins by presenting selected results oftwo recent studies conducted at EnvironmentCanada’s Emissions Research and MeasurementDivision. The first study (Baas and Graham,2006a, b, c) was conducted over 2 years (2004–05)and involved four light duty gasoline vehicles ofdifferent technologies operating on low blendethanol gasolines at two test temperatures (20 and�10 1C). The tailpipe emissions were characterizedfor criteria pollutants (CO, NOX, NMHC, NMOG),greenhouse gases (CO2, CH4, N2O), and particulatematter (PM2.5). Detailed speciation was completedfor non-methane hydrocarbons, carbonyl com-pounds, vapor phase organic acids, sulphur dioxide,ammonia, polycyclic aromatic hydrocarbons, andparticulate matter (organic and elemental carbon,particle phase organic and inorganic ions). Eva-porative emissions at 20 1C were also quantified andcharacterized for NMHC. Only the criteria, green-house gas, and selected air toxic emissions are
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presented in this paper. The second study (Belisleand Graham, 2006), conducted in November andDecember of 2005, involved paired flexible fuel andconventional vehicles with the objective to evaluatechanges in emissions due to flexible fuel vehicle(FFV) operation on gasoline and E85 as comparedto similar conventional vehicles operating on gaso-line. Emissions characterization included criteriapollutants (CO, NOX, NMHC, NMOG) and green-house gases (CO2, CH4, N2O). Detailed speciationwas completed for NMHC and carbonyl com-pounds. Since the results of individual studies oftencontradict one another, we also present statisticalanalyses of the results of these two studies,combined with literature results, in order to presenta clearer picture of potential emissions changes dueto use of either low ethanol gasolines or E85.
2. Methodology
Many of the test procedures used in these twostudies are common and are summarized below.Differences between the two test programs, wherethey exist, are noted.
2.1. Tailpipe emissions
Emissions measurements were conducted usingthe chassis dynamometer testing facility at theEmissions Research and Measurement Division ofEnvironment Canada. The procedures used aredetailed in the US EPA Federal Code of Regula-tions, Schedule 40 Part 86. For the low blendethanol study, a four-phase implementation of theFTP was used rather than the usual three-phaseFTP in order to facilitate particulate matter samplecollection. The FTP is representative of a non-demanding style of urban driving and allows forcomparison of cold- and hot-start emissions. Emis-sions were also characterized on the US06 cycle tocapture emissions during aggressive and high speeddriving. For the E85 study, emissions were char-acterized for each phase of the standard three-phaseFTP cycle, with a 10-min soak between Phases 2and 3. Samples for determining emissions of CO,CO2, NOX, and total hydrocarbons (THC) werecollected on a per phase basis. For each diluteexhaust sample collected, a corresponding dilutionair sample was collected. Dilute exhaust samplesfor determining methane, nitrous oxide, ethanol,and for speciation of NMHC were collected ona per phase basis. A single dilution air sample
was collected over each test (FTP or US06). Forthe carbonyl compound analysis, dilute exhaustsamples were collected on a per phase basis andone dilution air sample was collected over eachsampling day.
2.2. Evaporative emissions
For the low blend ethanol study, evaporativeemissions were measured over the 1 h diurnal heatbuild and hot soak cycles. The diurnal heat buildcycle simulated non-running emissions released asfuel in the vehicle expands as a result of increases inambient temperature. The hot soak cycle simulatesnon-running emissions released after the vehicle hasbeen running for a period of time. Although thevehicle has been turned off, residual heat from theengine continues to heat the fuel system compo-nents, causing evaporative emissions. Samples fordetermining evaporative emissions were automati-cally taken from the SHED at the end of each cycle.These samples were immediately directed to theautomated analyzer. Separate samples for determin-ing evaporative emissions of NMHC and ethanolwere drawn from the SHED and collected inTedlarTM bags.
2.3. Analytical methods
All analytical methods used in these studies areaccredited to ISO 17025 standards.
Concentrations of CO, CO2, NOX, and THCwere determined with standard test cell analyzers(non-dispersive infrared, chemiluminescence, andflame ionization). Concentrations of ethanol weredetermined using an Innova Model 1312 Photo-acoustic Multi-Gas Analyzer following proceduressimilar to Loo and Parker (2000).
Samples for determining carbonyl compoundswere collected on Sep-Pak silica cartridges coatedwith 2,4-dinitrophenylhydrazine (DNPH). The sam-ples were extracted and analyzed by reverse phasehigh performance liquid chromatography using anAgilent 1100 Series Liquid Chromatograph with anultraviolet–visible (UV–vis) diode array detector. Atotal of 18 carbonyl compounds (C1–C8) weredetermined using this method.
Approximately, 160 NMHC were determinedusing a Hewlett-Packard 6890 gas chromatograph(GC) with a flame ionization detector (FID). AnEntech M7000 cryogenic concentrator was used forsample concentration and introduction.
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Methane was determined and confirmation ofthe C2 and C3 hydrocarbons was accomplished bysimple gas loop injection onto a capillary column. AHewlett-Packard 6890 gas chromatograph equippedwith a gas sampling valve and a FID was used forthe analysis.
Nitrous oxide was determined using a Hewlett-Packard 5890A Series II GC with an electroncapture detector.
The detection limits for each method and sampletype are summarized in the Supplementary materialalong with details of the analytical methods.
2.4. Low blend study
2.4.1. Test vehicles
Three multi-port fuel injected (MPFI) vehiclesrepresenting different technologies (emission stan-dards) and one gasoline direct injection (GDI)vehicle were tested. These vehicles were a 1998Ford Escort ZX2 (US EPA Tier 1 emissionstandard, approximately 80,000 km), a 2001 NissanSentra CA (California SULEV zero evaporativeemission standard, approximately 12,000 km), a2003 Dodge Caravan (US EPA LEV emissionstandard, flexible fuel, approximately 25,000 km),and a 2000 Mitsubishi Dion Exceed (Japanese LEVemission standard, not currently sold in NorthAmerica, approximately 25,000 km). The Escortand the Sentra were tested at 20 and �10 1C. TheCaravan and the Dion were tested at 20 1C only.Tests were performed using four summer grade fuels(for tests at 20 1C) and four winter grade fuels(for tests at �10 1C).
2.4.2. Test fuels
The test fuels were blended for this project byHalterman Fuels of Texas and were designed to
Table 1
Low blend ethanol gasoline study fuel properties
Summer grade fuels
S-E0 S-E10 S-E10-Spl
Specific gravity (kgL�1) 0.705 0.725 0.717
Net heating value (BTU lbm�1) 18,927 18,127 18,182
Fuel fraction oxygen 0 0.036 0.036
Sulphur content (ppm) 34 34 31
Benzene (vol%) 0.1 0.5 0.7
Total aromatics (vol%) 7.9 11.0 8.1
Motor octane number 86.0 85.0 89.0
RVP (psi) 8.8 8.6 9.4
have matching octane number, fuel sulphur content,and vapor pressure within each seasonal grade. Foreach seasonal grade, the test fuels included a basefuel containing no ethanol, a 20% ethanol tailorblend, a 10% ethanol tailor blend, and a 10%ethanol splash blend. The splash blend fuels weremade by simply ‘‘splash’’ blending a volume ofethanol with the base fuel, resulting in lowersulphur, higher octane, and higher vapor pressurethan the base fuel. Selected fuel properties arepresented in Table 1. Complete fuel specificationsare given in the Supplementary material.
2.4.3. Test procedure
As the vehicles used for testing were in-use andpotentially exposed to gasoline with sulphur contenthigher than the test fuels, it was necessary toperform a conditioning sequence on each vehicleto remove residual sulphur from the catalyticconverter. The procedure involved running thevehicle at a rich air/fuel ratio and at a high catalysttemperature to facilitate the formation of hydrogensulphide from the residual sulphur on the catalystand is described in more detail in Durbin et al.(2003).
The charcoal canister of the vehicle collectsevaporative hydrocarbon emissions during theSHED tests, which are then purged into the enginewhile driving. These canisters are never fully purgedbut maintain a fixed amount of trapped vapor calledthe canister ‘‘heel’’. This presented a problembecause of the possibility of carryover of fuelvapors. To mitigate this problem, two new OEMcanisters were purchased for each vehicle at thebeginning of the program and seasoned using thesummer grade E0 fuel. The 20 1C testing beganusing the first canister, and the fuels were tested inascending ethanol content starting with the base
Winter grade fuels
S-E20 W-E0 W-E10 W-E10-Spl W-E20
0.734 0.693 0.726 0.705 0.714
17,319 18,975 18,096 18,200 17,494
0.073 0 0.036 0.037 0.073
35 33 33 26 27
0.8 0.5 0.5 0.4 0.3
14.1 8.3 12.6 7.3 6.3
85.7 85.0 84.3 89.5 90.0
8.7 13.4 13.1 13.8 13.2
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Table 2
E85 study fuel properties
E85 California RFG
Phase 2
Specific gravity (kgL�1) 0.784 0.743
Net heating value (BTU lb�1) 13,867 18,132
Fuel fraction oxygen 0.294 0.018 (MTBE)
Sulphur content (ppm) 17 37
Benzene (vol%) n/a 0.8
Total aromatics (vol%) 6.6 26.2
Research octane number 104 96.8
RVP (psi) 7.3 5.7
L.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–45164502
fuel. Before the repeat 20 1C tests were performed,the first canister was replaced with the secondseasoned canister. The repeat base fuel tests weretherefore performed with identical canister condi-tions as the initial base fuel tests.
To prepare for the �10 1C testing, the firstcanister was purged continuously for approximately4 weeks alternately with pressurized clean air andunder vacuum to remove as much of the canisterheel as possible. The �10 1C testing began using thesecond canister and the fuels were tested inascending ethanol content starting with the basefuel. Before the repeat �10 1C tests were performed,the first canister was re-installed. Although it hadbeen exposed to ethanol fuels from the 20 1C testing,it was hoped that the purging process removed mostof the ethanol contamination making the initial andrepeat base fuel tests as similar as possible withregards to canister conditions. The vehicle prepara-tion and test sequence that was followed is providedin the Supplementary material.
2.5. E85 study
The objective of this project was to determinewhether FFVs, when run on regular gasoline,produced increased emissions as compared tooperation on E85 and as compared to conventionalvehicles of the same make and model operating ongasoline.
2.5.1. Test vehicles
Two 2002 Chrysler Caravans meeting CaliforniaLEV 1 LDT emission standards, each with approxi-mately 50,000 km; and two 2004 Chrysler Sebringsmeeting California ULEV 1 emission standards,each with approximately 50,000 km were selectedfor the study. These vehicles were obtained fromfederal fleet operators in the Ottawa, Canadaregion. Upon receipt of the test vehicles, it wasdetermined that the conventional Sebring did notmeet the same emission standards as its flexible fuelcounterpart and therefore would not render validcomparisons. A suitable replacement vehicle couldnot be found, so the project was continued usingonly three vehicles.
2.5.2. Test fuels
The three vehicles were tested on the currentcertification gasoline (California RFG Phase 2certification fuel). The two FFVs were also testedon a commercial E85 blend obtained from a local
distributor. The fuel parameters are summarizedin Table 2.
2.5.3. Test procedure
The vehicles were fuel exchanged to the certifica-tion fuel and the evaporative emissions controlsystems were purged with butane as prescribed inthe FTP procedure. The vehicles were driven overtwo repeats of the LA4 cycle, fuel exchanged againand driven over two more repeats of the LA4 cycle.The conventional vehicle was ready for emissionstesting at this point.
Being designed to be capable of running onethanol–gasoline blends of up to 85% ethanol, theFFV fuel system incorporates a fuel compositionsensor that measures ethanol content in the fuel.This information is used to adjust the engineparameters to best suit the fuel blend. The statusof this sensor can be surveyed through the OBD IIsystem. It was observed in other testing at thelaboratory that the fuel sensors took longer thanexpected to report the correct ethanol reading,although according to one vehicle manufacturerrepresentative, the sensor should nearly instantlysense the fuel composition. At the beginning of thestudy, additional mileage accumulation was per-formed on the two FFVs until the fuel sensor readthe correct fuel composition (zero ethanol). After afinal fuel exchange and overnight soak, three repeatsof the FTP were conducted with emissions char-acterization over consecutive days. The two FFVswere then fuel exchanged to E85 and immediatelytested for emissions while the fuel sensor wasreading incorrectly. After fuel exchanges and mile-age accumulation on E85, with periodic checks toensure the fuel sensor was reading the fuelcomposition correctly, the FFVs were again tested
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for three repeats of the FTP with emissionscharacterization on consecutive days.
3. Results
3.1. Low blend ethanol study
The complete set of measured emission rates isprovided in the Supplementary material.
ANOVA and regression analyses were used toidentify and evaluate changes in emissions due to fuelethanol content. For the regression analysis, theemission rate was plotted as a function of fuel ethanolcontent and the slope of the regression line and its 95%confidence limits were determined. If the confidencelimits did not include zero, then the slope wasconsidered statistically significantly different from zero.
The Caravan ‘‘flex fuel’’ operation during thistesting program was found to be unreliable ascontinuous monitoring of the on-board fuel ethanolsensor showed a fuel composition of zero ethanolfor all test fuels. Therefore, it is possible that theengine did not realize any specially designed engineparameters for ethanol fuel operation.
3.1.1. Criteria emissions
The usual trends of generally increased emissionson cold start and cold temperature operation andduring aggressive driving were observed with thesevehicles and will not be further discussed.
The FTP composite and US06 emission rates foreach vehicle and fuel are shown in Fig. 1. The slopesobtained from the regression analyses are presentedin the Supplementary material. A negative slopewas observed for CO, a positive slope for NOX,and a slope of approximately zero was observedfor NMHC and NMOG; however, most of theobserved trends were not statistically significantlydifferent from zero.
Referring to the per phase emission rates pre-sented in the Supplementary material, ethanolblends tended to decrease the CO emissions andincrease the NOX emissions primarily during enginecold start and aggressive driving conditions for theMPFI and GDI vehicles. There was minimal effectduring hot engine start and stabilized driving. Thereason for the elevated NOX emissions from theSentra with E20 fuel at �10 1C for both the FTPand US06 is not known.
Compared to the E10 tailor blend fuel, the splashblended E10 fuel resulted in 35–50% higher COemissions during cold engine start at cold tempera-
ture for the MPFI vehicles. At 20 1C, there was nostatistical difference in CO, NOX, NMHC orNMOG emissions between the two fuels for anyof the vehicles.
As shown in Fig. 1, fuel ethanol content did notaffect the specific reactivity or ozone formingpotential of the exhaust from the MPFI vehicles.For the GDI vehicle, increasing fuel ethanol contentresulted in decreasing specific reactivity and ozoneforming potential of the exhaust.
3.1.2. Air toxic emissions
The FTP composite and US06 emission rates foreach vehicle and fuel are shown in Fig. 2. The slopesobtained from the regression analyses are presentedin the Supplementary material. Formaldehyde andacetaldehyde emissions tended to increase, and 1,3-butadiene and benzene emissions tended to decreasewith increasing ethanol content. The changes forformaldehyde, 1,3-butadiene, and benzene were notstatistically significant while the changes in acet-aldehyde were nearly always statistically significant.The benzene response to change in ethanol contentshould be considered with caution as the totalaromatics and benzene content of the fuels weredifferent but did not change as a direct function ofethanol content as shown in Table 1.
Referring to the Supplementary material, thepresence of ethanol in the fuel increased theformaldehyde and acetaldehyde emissions primarilyduring cold engine start and under aggressivedriving conditions, not usually for the hot start orstabilized driving. There were no statistically sig-nificant differences in these air toxic emissionsbetween the E10 and E10-splash fuels.
For all vehicles, ethanol emissions were highestfor cold engine start. Once the catalyst was up tonormal operating temperature, ethanol emissionswere essentially not measurable. Operation at coldtemperature resulted in higher ethanol emissionrates as compared to standard temperature andmainly affected cold engine start emissions. Rela-tively low ethanol emissions were present duringsome of the tests with E0 fuel, likely due to hang upof ethanol in the vehicle fuel system. These findingsindicate that the canister conditioning and vehiclepreparation procedures minimized but did notcompletely eliminate fuel carry-over.
3.1.3. GHG emissions
The FTP composite and US06 emission rates foreach vehicle and fuel are shown in Fig. 3. The slopes
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Dion(20C)
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
FPT
Form
alde
hyde
(mg/
km)
E0 E10
E10-Spl E20
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
US
06 F
orm
alde
hyde
(mg/
km)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
FPT
Ace
tald
ehyd
e (m
g/km
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
US
06 A
ceta
ldeh
yde
(mg/
km)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
FPT
Acr
olei
n (m
g/km
)
0.0000.0050.0100.0150.0200.0250.0300.0350.040
US
06 A
crol
ein
(mg/
km)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
FPT
1.3-
But
adie
ne (m
g/km
)
0.00
0.05
0.10
0.15
0.20
US
06 1
.3-B
utad
iene
(mg/
km)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
FPT
Ben
zene
(mg/
km)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
US
06 B
enze
ne (m
g/km
)
Fig. 2. Comparison of FTP composite and US06 toxic emissions from the low blend study.
L.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–4516 4505
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obtained from the regression analyses are summar-ized in the Supplementary material.
For all vehicles and test temperatures, distance-based CO2 emission rates were essentially un-changed as ethanol content increased. The lowervolumetric energy density of the ethanol blend fuelscanceled out the lower carbon content.
In general, increasing ethanol content did notresult in any statistically significant changes to theCH4 emission rates. The exception was the Escortwhere CH4 emission rates decreased with increasingethanol content at 20 1C only. N2O emissions ingeneral tended to increase with ethanol content,though some changes were not statistically signifi-cant. The exception was the Sentra where there was
0
50
100
150
200
250
300
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
FTP
Com
posi
te C
O2
(g/k
m) E0 E10
E10-Spl E20
0
5
10
15
20
25
FTP
Com
posi
te N
2O (m
g/km
)
0
5
10
15
20
25
30
FTP
Com
posi
te C
H4
(mg/
km)
Fig. 3. Comparison of FTP composite and US06 emissions f
no change at 20 1C but a statistically significantdecrease at �10 1C.
3.1.4. Evaporative emissions
The evaporative emissions results are shown inFig. 4. The differences in evaporative emissionsstandards were quite evident with these vehicles.The Sentra had the lowest diurnal and hot soakNMOG emissions (o0.04 g per test). The Caravanand the Escort had similar diurnal and hot soakNMOG emissions (o0.7 and o0.25 g per test,respectively). The Dion had the highest diurnal andhot soak NMOG emissions with diurnal emissionsapproaching 8 g per test and hot soak emissionsaround 1.5 g per test. The response of NMOG
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
Escort(20C)
Escort(-10C)
Sentra(20C)
Sentra(-10C)
Caravan(20C)
Dion(20C)
0
50
100
150
200
250
300
US
06 C
O2
(g/k
m)
02468
1012141618
US
06 N
2O (m
g/km
)
0
5
10
15
20
25
30
US
06 C
H4
(mg/
km)
or greenhouse gas emissions from the low blend study.
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0.001
0.01
0.1
1
10
100
0
Eva
p N
MO
G (g
/test
)
0.1
0.2
0.3
0.4
0.5
0.6
Diurnal
Escort
Eva
p E
than
ol (m
g/te
st)
E0 E10
E10-Spl E20
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Eva
p S
peci
fic R
eact
ivity
(g O
3/g
NM
OG
)
0.001
0.01
0.1
1
10
100
Soak
Eva
p O
FP (g
O3/
test
)
Diurnal Soak Diurnal Soak Diurnal Soak
Sentra Caravan Dion
Diurnal
Escort
Soak Diurnal Soak Diurnal Soak Diurnal Soak
Sentra Caravan Dion
Diurnal
Escort
Soak Diurnal Soak Diurnal Soak Diurnal Soak
Sentra Caravan Dion
Diurnal
Escort
Soak Diurnal Soak Diurnal Soak Diurnal Soak
Sentra Caravan Dion
Fig. 4. Comparison of evaporative emissions from the low blend study.
L.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–4516 4507
emissions to ethanol content was different for eachvehicle as shown in Fig. 4. The results of theregression analysis are summarized in the Supple-mentary material and show that each vehicleresponds differently, and that in general, theresponses were not statistically significant. Thedifferences observed between the E10 and E10-splash fuels were also not statistically significant.
3.2. E85 study
The complete set of measured emission ratesis provided in the Supplementary material. FTPcomposite emission rates are compared in Figs. 5–7.
3.2.1. Criteria emissions
The first step of the study was to determine if thepaired vehicles differed in emissions when operatedon certification fuel. Since the conventional Sebringwas certified to a different emission standard thanthe FFV Sebring, it was excluded from the study. Asseen in Figs. 5 and 6, the two Caravans showed nostatistically significant differences in emissions,except for NOX for which the FFV showed 23%
lower emissions than the conventional vehicleduring Phase 1 of the FTP.
When compared to the conventional Caravanon certification 2 fuel, the FFV Caravan on E85showed statistically significant decreases in CO,NOX, and NMHC emissions by 72%, 48%, and55%, respectively. There was no statistically sig-nificant difference in NMOG emissions.
For the FFV Caravan, operation on E85 resultedin statistically significant decreases in CO, NOX andNMHC emissions but no change in NMOGemissions, as compared to operation on certificationfuel. The decreases in CO and NMHC emissionsoccurred in Phases 1 and 3 while the decrease inNOX emissions occurred only in Phase 1.
For the FFV Sebring, operation on E85 alsoresulted in statistically significant decreases in CO,NOX, and NMHC emissions, as compared tooperation on certification fuel. The decrease in COoccurred across all three phases. The decreases inNOX and NMHC emissions occurred in Phases 1and 3. While there was no statistically significantchange in FTP composite NMOG emissions, Phase1 showed a statistically significant increase andPhase 3 showed a statistically significant decrease.
Fig. 5. Criteria emissions for conventional and flexible fuel vehicles operating on Cal. RFG 2 fuel and E85.
L.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–45164508
3.2.2. Air toxic emissions
Fig. 6 shows FTP composite emission rates forselected air toxics. As summarized in the Supple-mentary material, there were no statistically signi-ficant differences in air toxic emissions between theconventional Caravan and FFV Caravan operatingon certification fuel. Operation of the FFV on E85resulted in no statistically significant change informaldehyde emissions, a statistically significantincrease in acetaldehyde emissions, and statisticallysignificant decreases in benzene and BTEX emis-sions, as compared to the conventional Caravan.Comparing the FFV Caravan operation on E85 toits operation on the certification fuel, similar trendsto the conventional Caravan were observed, except
now, a statistically significant increase in formalde-hyde emissions was observed. Comparing the FFVSebring operation on E85 to its operation on thecertification fuel, similar trends to the FFV Caravanwere observed. The 1,3-butadiene emissions fromall vehicles on the certification fuel were belowdetection limits so changes could not be reliablyevaluated.
3.2.3. GHG emissions
Fig. 7 shows FTP composite emission rates forthe greenhouse gases. As summarized in theSupplementary material, there were no statisticallysignificant differences in GHG emissions betweenthe conventional Caravan and the FFV Caravan
Fig. 6. Air toxic emissions for conventional and flexible fuel vehicles operating on Cal. RFG 2 fuel and E85.
L.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–4516 4509
operating on certification fuel. The FFV Caravanoperating on E85 showed a statistically significantdecrease in N2O emissions but no change in CH4
emissions, as compared to the conventional Caravanoperating on Certification fuel. The CH4 change wasalmost significant at the 0.05 level (p-value ¼ 0.058).
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0
50
100
150
200
250
300
350
Conv Caravan
FTP
CO
2 (g
/km
)
Cal. RFG 2E85
0
2
4
6
8
10
12
FTP
CH
4 (m
g/km
)
0
5
10
15
20
25
FTP
N2O
(mg/
km)
FFV Caravan FFV Sebring
Conv Caravan FFV Caravan FFV Sebring
Conv Caravan FFV Caravan FFV Sebring
Fig. 7. Greenhouse gas emissions for conventional and flexible fuel vehicles operating on Cal. RFG 2 fuel and E85.
Caravan
0
10
20
30
40
50
60
70
0Accumulation (km)
Fuel
Ses
nor (
%E
than
ol)
Sebring
0102030405060708090
0Accumulation (km)
Fuel
Ses
nor (
%E
than
ol)
100 200 300 400 500 100 200 300 400
Fig. 8. Fuel sensor change by mileage accumulation. Solid symbols indicate fuel exchange or top-up prior to mileage accumulation to
reach that point.
L.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–45164510
The FFV Caravan, when operating on E85, showeda statistically significant increase in CH4 emissionsand no statistically significant change in N2Oemissions, as compared to operation on Certificationfuel. The N2O change was almost significant atthe 0.05 level (p-value ¼ 0.084). The FFV Sebringalso showed a statistically significant increase inCH4 emissions and a statistically significant decreasein N2O emissions, as compared to operation onCertification fuel.
3.2.4. Fuel sensor behavior
Fig. 8 shows how the FFVs’ sensors changed asmileage accumulated. The FFV Caravan’s sensor,over 356 km, changed from 0% to 64%. The FFVSebring’s sensor, over 273 km, changed from 0% to83%. Fig. 1a and b in the Supplementary materialshows linear trend lines fit to the measured emissionrates as a function of fuel sensor reading. All testsshown in these figures were conducted on E85 andthe sensor reading was recorded at the beginning of
ARTICLE IN PRESSL.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–4516 4511
the test. For the FFV Caravan, regression analysisshowed that CO, NOX, and NMHC emissionsdecreased and NMOG emissions increased duringPhase 1 of the FTP as the sensor adjusted to thefuel composition. The Phases 2 and 3 trend linesshowed no statistically significant change in emis-sions with fuel sensor change. For the Sebring, COand NOX emissions decreased as the sensor readingincreased during all three phases. These changeswere not statistically significant for Phases 2and 3, but were statistically significant for Phase 1.For NMHC and NMOG, emissions increasedduring Phase 1 but no change was observed duringPhase 2 or 3.
4. Discussion
We have reported the results of two studies thathave examined the effect on emissions due to the useof ethanol-blended gasolines. These two studies, likeother studies reported in the literature, are limited(mainly for financial reasons) to a fleet of a few testvehicles. The question of how representative anyone of these test vehicles is of the population fromwhich it is taken is always asked. As can be seenfrom the literature reviews discussed below, resultsfrom individual studies often show contradictingresults, and one reason for this is the small fleet sizeof any one study. In order to clear away some ofthese contradictions, we take the results of thecurrent studies and combine them with the resultsreported in the literature to increase the fleet size. Itis expected that, as a result, a clearer picture of theeffects on emissions will be obtained.
4.1. Literature review E10
Direct comparisons between reference fuels andE10 blends for FTP composite emission rates werepossible for two published studies (Knapp et al.,1998; Durbin et al., 2006) in addition to the resultsfrom this study. Changes in criteria emissions, airtoxic and GHG emissions (CO, NOX, NMHC,NMOG, formaldehyde, acetaldehyde, 1,3-buta-diene, benzene, CO2, N2O, CH4) as a result of fuelchange were analyzed. Knapp et al. did not reportNMHC, NMOG, or GHG emission rates. Durbinet al. did not report N2O or CH4 emission rates. Atotal of 43 vehicle/fuel pairs were available fromthese studies.
For two of the three studies, individual test resultswere available for each vehicle, so tests for
significance could be done for the changes resultingfrom individual vehicle/fuel pairs. For each vehicle/fuel pair, the relative change in emission rate((E10-Ref)/Ref) was calculated to minimize theeffect of different emission control technologies.The relative change data was examined to determineif it was normally or symmetrically distributed. TheKolmogorov–Smirnov goodness of fit test and Q–Qplots were used to compare each dataset to thenormal distribution. The skewness parameter wasalso calculated. Descriptive statistics are summar-ized in Table 3 and the relative changes for eachvehicle/fuel pair are provided in the Supplementarymaterial.
In all cases, the data were not normally dis-tributed and almost always moderately to highlyskewed; therefore, the median value instead of themean was used for quantifying the change due tofuel. From the results of the entire dataset, allchanges in emissions were statistically significantexcept for NOX, formaldehyde and the GHGs. Forthe 31 or 32 tests for which individual tests forsignificance could be done, only a few of theindividual vehicles showed a statistically significantchange for all pollutants except acetaldehyde.Because of the magnitude of the change inacetaldehyde emissions, 11 of the 31 vehiclesshowed statistically significant changes. These sta-tistically significant changes were in the samedirection as the entire dataset, and at least twicethe magnitude of the median value of the entiredataset. The box plot shown in Fig. 9 illustratesthese results.
4.2. Literature review E85
Direct comparisons between reference fuels andE85 blends for FTP composite emission rates werepossible for four published studies (Benson et al.,1995; Kelly et al., 1996; Winebrake and Deaton,1999; Black et al., 1998) in addition to the resultsreported in this study. Winebrake and Deatonreported only toxic emissions. A total of 11vehicle/fuel pairs were included in the dataset. Therelative changes for each vehicle/fuel pair areprovided in the Supplementary material. The resultsfrom the literature for E85 were generally for oldervehicles than those in the E10 comparison and thepresent study.
The analysis described above for E10 was con-ducted and the results are summarized in Table 3. Inall cases, the datasets were not normally distributed
ARTIC
LEIN
PRES
STable 3
Summary of descriptive statistics and results of test for significance for relative changes in emissions due to the use of ethanol blended fuels
Fig. 9. Box plot showing relative change in emissions with fuel change from reference fuel to E10 for combined data from published
studies and this study.
L.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–4516 4513
and also generally not symmetrically distributed.Statistically significant changes in emissions werefound for all pollutants except CO and NMOG.Individual test data were available for between threeand seven vehicles for each pollutant, allowingindividual tests for significance to be done (seeSupplementary material). Since the changes inemissions were generally much larger than seenfor E10, the sign and magnitude of the individualtests for significance agree quite well with whatthe entire dataset suggests. The exception to thistrend is CO, which showed a much wider variationin effect. Upon closer examination, it appearsthat the older vehicles (Tier 0 and older) havedifferent CO and NMOG responses than newervehicles (Tier 1 and newer). Four of the five oldervehicles showed large increases in CO emissions,while the newer vehicles showed a decrease inCO emissions of similar magnitude. Three ofthese five older vehicles also showed a greaterincrease in NMOG emissions than the decreaseshown by the newer vehicles. The box plot inFig. 10 illustrates these results. These changes weregenerally consistent with those used by Jacobsonin a recent assessment of potential health effectsof widespread E85 use in the USA (Jacobson,2007).
5. Conclusions
The results of two recent studies on the effects ontailpipe and evaporative emissions of low blendethanol gasolines and E85 were presented. Theresults from these two studies were combined withpublished literature results to better assess the effectof ethanol on vehicle emissions.
The results of the low blend ethanol gasolinestudy suggests that up to 20% ethanol can lead tostatistically significant reductions in FTP compositeemissions of CO, statistically significant increasesin NOX and acetaldehyde emissions, and no changein NMHC, NMOG, formaldehyde, 1,3-butadiene,Benzene, or GHG emissions. The magnitude of thechange appears to depend on vehicle technologyfor the four vehicles studied. Much smaller changeswere observed for US06 emissions. Operation atcold temperature tended to increase the magnitudeof the emissions and the magnitude of the changesbut not, in general, the direction of the changes.Low blend ethanol gasolines showed no statisticallysignificant effect on evaporative NMOG emissions.While changes in the detailed composition of thetailpipe and evaporative emissions were observed(increases in acetaldehyde and ethanol, decreasesin gasoline hydrocarbons), there appeared to be
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Acetald Benzene Butadiene CO Formald NMHC NMOG NOX
-20
0
20
40
60
Rela
tive C
hange (
E85-R
ef)
/Ref
Benzene Butadiene CO Formald NMHC NMOG NOX
-2
-1
0
1
2
Fig. 10. Box plot showing relative change in emissions with fuel change from reference fuel to E85 for combined data from published
studies and this study.
L.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–45164514
no net effect on the specific reactivity of theemissions. There were also no statistically signifi-cant differences in emissions from the E10 andE10-splash fuels, except during cold temperaturecold start where an increase in CO emissions wasobserved.
The results of the E85 study indicate that the onlystatistically significant difference in emissions betweenthe conventional Caravan and the FFV Caravancertified to the same emission standard and operatingon certification fuel was a 23% decrease in NOX
emissions for the FFV Caravan. Operation of theFFV Caravan and the FFV Sebring on E85 resultedin statistically significant increases in formaldehyde(86–117%), acetaldehyde (1300–5000%) and methaneemissions (37–49%); statistically significant decreasesin CO (37–60%), NOX (32–47%), NMHC (3–45%),benzene (58–72%) emissions and no statisticallysignificant changes in NMOG, 1,3-butadiene, CO2,or N2O emissions. Results also suggest that it takessome time for the fuel oxygen sensor to respond tothe step change in change fuel composition thatoccurred on fuel exchange from certification fuelto E85. It appeared that for both vehicles, theobserved changes in fuel composition during300+km mileage accumulation were associated withfuel exchange or top-up followed by mileage accu-mulation, not just mileage accumulation. Limitedemissions testing was conducted while the fuel sensor
was adjusting to the fuel composition and theseresults show that CO and NOX emissions can behigher while NMHC and NMOG emissions canbe lower while the fuel sensor is adjusting to thecorrect fuel composition. The differences are largestduring cold start but in some cases are observedduring all phases of the test.
For low blend ethanol fuels and E85, unburnedethanol was found almost exclusively during coldand hot engine start portions of the test, when thecatalytic converter was cold, not during stabilizedoperation or during aggressive driving, when thecatalytic converter was hot. Ethanol was found inthe evaporative emissions during the low blendethanol study and increased with increasing ethanolcontent. The difference in RVP of the E10 and E10-splash blends did not appear to increase ethanol orNMOG evaporative emissions.
When reviewing the conclusions of each studyindividually, contradictory results are often found.But, when all available data for a particular ethanolblend is considered as a single dataset, as done inthis paper, the following general conclusions can bedrawn.
As compared to reference fuels with no ethanol,operating on E10 blends generally result in:
�
statistically significant decreases in CO emissions(�16%),
ARTICLE IN PRESSL.A. Graham et al. / Atmospheric Environment 42 (2008) 4498–4516 4515
�
statistically significant increases in NMHC (9%),NMOG (14%), acetaldehyde (108%), 1,3-buta-diene (16%), and benzene (15%) emissions, and � no statistically significant change in NOX, for-
maldehyde, CO2, CH4, or N2O emissions.
The increase in benzene emissions may seemcurious as one may expect a dilution effect pro-portional to the ethanol content. This may resultfrom differences in benzene and/or total aromaticcontent of the reference and E10 fuels as not allfuels were splash blends of ethanol with thereference fuel.
As compared to reference fuels with no ethanol,operating on E85 generally results in:
�
statistically significant decreases in NOX (�45%),NMHC (�48%), 1,3-butadiene (�77%), andbenzene (�76%) emissions, � statistically significant increases in formaldehyde
(73%) and acetaldehyde (2540%) emissions, and
� no statistically significant change in CO, CO2, or
NMOG emissions.
While each of the individual studies generallyfollowed the trends suggested by the analysis of theaggregated datasets, some differences in conclusionswere found. This finding reinforces the importanceof having a large enough vehicle fleet to minimizeinfluences of a single vehicle on the conclusionsdrawn and to increase the ability to detect smallerchanges.
Acknowledgements
The authors would like to acknowledge the vehicletesting and chemistry laboratory staff of EnvironmentCanada’s Emissions Research and Measurement Divi-sion for their efforts in conducting the emissions testingand analyses reported in this paper. Funding for thelow blend ethanol study was provided by NaturalResources Canada’s Program for Energy Researchand Development and Environment Canada. Vehiclesfor this study were provided by Transport Canada’sAdvanced Technology Vehicle program (Nissan Sentraand Mitsubishi Dion) and by Natural ResourcesCanada (FFV Caravan).
Funding for the E85 study was provided byNatural Resources Canada and the federal fleetmanagers’ Federal Vehicles Initiative (FVI). Vehi-cles for this study were provided by the federal fleet
managers of Natural Resources Canada and theRoyal Canadian Mounted Police.
The authors would also like to thank Dr. ThomasDurbin for providing the individual test results forthe CRC E-67 study.
Appendix A. Supplementary materials
Supplementary data associated with this articlecan be found in the online version at doi:10.1016/j.atmosenv.2008.01.061.
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