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Atmospheric Environment 84 (2014) 339e348

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Atmospheric Environment

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Emissions characterization from EURO 5 diesel/biodiesel passengercar operating under the new European driving cycle

M. Lopes a, L. Serrano b,c, I. Ribeiro a,*, P. Cascão d, N. Pires b, S. Rafael a, L. Tarelho a,A. Monteiro a, T. Nunes a, M. Evtyugina a, O.J. Nielsen e, M. Gameiro da Silva c, A.I. Miranda a,C. Borrego a

aCESAM & Department of Environment and Planning, University of Aveiro, 3810-193 Aveiro, Portugalb School of Technology and Management, Polytechnic Institute of Leiria, Morro do Lena, Alto do Vieiro, ap.4163, 2411-901 Leiria, PortugalcADAI, LAETA Department of Mechanical Engineering, University of Coimbra, Rua Pedro Hispano 12, ap.10131, 3030-289 Coimbra, Portugald Ecotech Pty Ltd, 1492 Ferntree Gully Road, Knoxfield, Victoria 3180, AustraliaeDepartment of Chemistry, University of Copenhagen, Universitetspaken 5, DK-2100 Copenhagen Ø, Denmark

h i g h l i g h t s

� A light EURO 5 diesel engine was tested using B0, B7 and B20, under the NEDC (New European Driving Cycle).� The exhaust emissions were measured and a VOC speciation was performed.� The most efficient fuel was B20 and the least combustion efficiency was found for B7.� The use of B7 may imply higher overall emissions than B0 and B20.

a r t i c l e i n f o

Article history:Received 23 July 2013Received in revised form18 November 2013Accepted 28 November 2013

Keywords:Biodiesel bendsEURO 5 passenger carNew European Driving CycleEmission measurements

* Corresponding author. Tel.: þ351 234 370 200; faE-mail address: ilavrador@ua.pt (I. Ribeiro).

1352-2310/$ e see front matter � 2013 Elsevier Ltd.http://dx.doi.org/10.1016/j.atmosenv.2013.11.071

a b s t r a c t

The increasing demand of petroleum based fuels and their use in internal combustion engines haveadverse effect on air quality and climate change. Production of biofuels promises substantial improve-ment in air quality through reducing emission from biofuel operated vehicles. In this study the influenceof the fuel mixture on EURO 5 vehicle exhaust emissions operating under the New European DrivingCycle (NEDC) and in hot operating conditions was analysed. Distinct diesel/biodiesel ratios (B0 (100%/0%),B7 (93%/7%) and B20 (80%/20%), volume basis) were considered. Experiments were conducted on achassis dynamometer examining several pollutants, namely: carbon dioxide (CO2), carbon monoxide(CO), nitrogen oxides (NO and NO2), particulate matter (PM10 and PM2.5) and total volatile organiccompounds (VOC). Moreover, a VOC speciation analysis by gas chromatography was performed toexplore the emission variations regarding a set of seventeen VOC.

The biodiesel fuel blends showed significant differences in combustion efficiency. An increasingamount of biodiesel in the fuel results in decreasing trends regarding NO, and particulate matteremissions. However, nitrogen dioxide and total VOC emissions increase with the biofuel content in thefuel. Moreover, the VOC speciation analysis suggests that the set of VOC present in exhausted gases isclearly fuel dependent.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

Global industrialization and growing motorization have led to asteep rise in the demand of petroleum-based fuels. Today, fossilfuels take up 80% of the primary energy consumed in the world, ofwhich 32% is consumed by the transport sector (IEA, 2011).

x: þ351 234 370 309.

All rights reserved.

Furthermore, fossil fuels provide a major contribution to green-house gas emissions (IPCC, 2007). Progressive depletion of con-ventional fossil fuels with increasing energy consumption andgreenhouse gas emissions, have led to a move towards alternativesbased on renewable, sustainable, efficient and cost-effective energysources with lesser emissions from the transport sector (2009/28/CE).

Vehicle emissions constitute one of the main sources of atmo-spheric pollution in modern cities (Monteiro et al., 2007; Ross et al.,2011). The increasing number of passenger cars, especially during

Table 1Technical specifications of the test vehicle.

Engine type Renault Mégane 1.5 dCi

Fuel injection system Direct injection, common-railCylinders/valves 4/8Displacement (cm3) 1461Maximum power (kW hP�1) 81/110Maximum torque (Nm) 240/1750 rpmWeight (kg) 1215Aerodynamic (S(M2)/Cd) 2.21/0.326Equipped with a DPF system Self-regeneratingEquipped with a EGR system e

M. Lopes et al. / Atmospheric Environment 84 (2014) 339e348340

the last decade, resulted in complex traffic problems with seriousconsequences on emissions and fuel consumption (ACEA, 2010).Diesel engines are the main power source in heavy-duty trucks andbuses and their share is rapidly growing in passenger cars as well.Almost half (48%) of new passenger cars in the European Union arebased on a diesel engine (ACEA, 2010). Through the last years,improving engines efficiency has been a concern in reducing thefuel consumption. An example of this improvement is shown by theevolution of emission standards for road transport in Europe(Vestreng et al., 2009) from 1992 (EURO 1) to the present. The NOx

emission standards for diesel passenger vehicles decreased 91%(from 0.90 to 0.08 g km�1). CO2 emissions decreased 13% from 2000to 2010 in the same type of vehicles (Fontaras et al., 2010). Besidesthe measures to improve the engine efficiency, recent diesel carsare equipped by default with diesel particulate filter systems,because this type of engine still has significant particulate emis-sions. According to (Bergmann et al., 2009; Tente et al., 2011), theuse of diesel particulate filter can reduce these emissions by morethan 90%. Moreover, these cars are equipped with an exhaust gasrecirculation system which is a well-established way of reducingNOx emissions, through adding exhaust gas to the airefuel mix. Theoxygen content of the mixture is reduced as well as the combustiontemperature, minimizing the production of NOx by 10e25% (Abd-Alla, 2002; Kaspar et al., 2003). More recently, modern technol-ogy heavy-duty passenger cars (Euro 6 compliant) are also fittedwith selective catalytic reduction systems to control NOx emissions.

On the other hand, over the last decade, the production andconsumption of biofuels increased rapidly worldwide (from 16billion litres in 2000 to more than 100 billion litres in 2011, ac-cording to the International Energy Agency web page e http://www.iea.org/topics/biofuels/) in an attempt to reduce greenhousegas emissions, to diversify transportation fuels, promote renewableenergy and create employment, especially in rural areas anddeveloping countries. Brazil is the most evident example. In theEuropean Union, the investment in the energy sector, namely onbiofuels, is one of the key strategies to meet the European com-mitments to the Kyoto Protocol and to develop a 2020 low carboneconomy.

Regarding biofuels, the European Union’s proposed scheme in-cludes sustainability criteria for biofuels and a goal of 10% ofrenewable energy in the transportation sector by 2020, asdescribed by the European Renewable Energy Directive (2009/28/EC). Portugal, as aMember State, intents not only tomeet this targetbut to consider a minimum of 10% of biofuels (biodiesel andbioethanol).

One of the most important differences between biodiesel andconventional diesel is the oxygen content. Biodiesel has 10e12%(mass basis) more oxygen than petroleum-based diesel whichmeans lower CO, particulate matter (PM) and non-methane volatileorganic compounds (NMVOC) emissions, but higher NOx emissionsand ozone-forming potential as well (Krahl et al., 2001; McCormicket al., 2006; Taylor, 2008; Demirbas, 2009; Gaffney and Marley,2009; Gupta and Demirbas, 2010; Serrano et al., 2011; Xue et al.,2011). Moreover, biodiesel has lower sulphur and aromatic con-tents than diesel and, unlike diesel, biodiesel is biodegradable andnontoxic (Gupta and Demirbas, 2010). In fact, emissions of gaseouspollutants are widely dependent on both fuel properties and ve-hicles technology (Gaffney and Marley, 2009). Several studies pointout that fuel blends, even with low content of biodiesel on diesel,can help to improve greenhouse gas and atmospheric pollutantemissions, and relieve the pressure on scarce resources withoutsignificantly limiting engine performance (McCormick et al., 2006;Serrano et al., 2011; Xue et al., 2011).

Lapuerta et al. (2008) reviewed the literature about biodieselemissions and concluded that: (1) NOx emission slightly increases

when using biodiesel fuels. The reason most frequently pointed outis that the fuel injection process is improved when using biodiesel;(2) PM emissions decrease considerably with biodiesel whencompared to diesel fuel, mainly caused by reduced soot formationand enhanced soot oxidation. The oxygen content and the absenceof aromatic content in biodiesel have been pointed out as the mainreasons; (3) Total hydrocarbons and CO emissions are usually foundto significantly decrease with biodiesel employment, due to a morecomplete combustion caused by the increased oxygen content inthe flame coming from the biodiesel molecules. However, biodieseleffects on CO, HC, and PM emissions vary significantly among ve-hicles, engine technology, and driving patterns (Karavalakis et al.,2009; Bakeas et al., 2011; Karavalakis et al., 2011; Randazzo andSodré, 2011).

Based on a set of diesel/biodiesel blends as fuel, some recentstudies (Karavalakis et al., 2009; Bakeas et al., 2011; Karavalakiset al., 2011; Randazzo and Sodré, 2011; Bermúdez et al., 2011;Kousoulidou et al., 2012) have been published contributing to theunderstanding of the engine behaviour in terms of emission andperformance profiles under specific driving cycles, such as the NewEuropean Driving Cycle (NEDC). However, these studies focused onthe EURO 3 and EURO 4 vehicle technology classes, thus referring toemission profiles of vehicles sold from 2000 to 2009.

Thework presented here evaluates the effects of diesel/biodieselblends on the fuel consumption and the gaseous emissions from anew diesel EURO 5 passenger vehicle, a Renault Megane 1.5 dCi(2011). The emissions were characterised considering CO2, CO, NO2,NO, VOC, PM10 and PM2.5. The studywasmade using the vehicle ina NEDC on a laboratory chassis dynamometer. Fuel blends con-taining 7%v/v (B7) and 20%v/v (B20) of soyabean/palm biodiesel(84%/16%), in volume basis, in petroleum-based diesel were testedand compared with a 100% diesel fuel (B0).

This experimental study contributes to a better characterizationof the emission factors of the vehicles using diesel/biodiesel blendsin order to understand the real impact of the use of this kind of fuel,as well as to improve the transport emission scenarios predicted forthe 2020 year (the target year of the Europe 20e20e20 strategy).

2. The test procedure

2.1. Test vehicle and fuels

The vehicle used in this experiment was a Renault Megane1.5 dCi (2011) equipped with a common-rail direct injection dieselengine and meeting EURO 5 emission standards. The technicalspecifications of the vehicle are listed in Table 1. This vehicle wasselected because it is the most sold vehicle in Portugal with 7324units sold between January and October 2011 (ACAP, 2011).

Modern diesel cars are equipped with diesel particulate filtersystems in order to fulfil the requirements of EURO 5 standard. Thisvehicle is also fitted with an exhaust gas recirculation system.

M. Lopes et al. / Atmospheric Environment 84 (2014) 339e348 341

The fuels used in this study were diesel (B0) and diesel/biodieselblends at proportions of 7%v/v and 20%v/v (B7 and B20); biodieselis produced from blend of soyabean (84%v/v) and palm (16%v/v).The fuel properties are presented in Table 2.

It is relevant to note the main differences when comparingbiodiesel with fossil diesel: biodiesel is more viscous, fuel diesel hasa higher heating value, biodiesel is denser and it has about 10e11%of oxygen content while petroleum-based diesel does not haveoxygen. These factors will influence the combustion process and,namely the fuel consumption and emission factors for somegaseous pollutants.

2.2. Driving cycles and measurement protocol

The experiments were carried out with the vehicle placed over achassis dynamometer (Fig. 1), according to the NEDC, simulatingthe typical usage of a car in Europe in order to quantify vehicleemissions under distinct driving conditions. The measurementprotocol was repeated four times per fuel, assuring the compara-bility of the emission measurements. Moreover, the exhaust gasesand the engine coolant temperatures were approximately 100 �Cand 80 �C, respectively, at the start of the test procedure, to guar-antee that each trial was performed at the same conditions. Thus,the concentration measurements were performed under hotconditions.

The NEDC, described in detail by the Directive 70/220/EEC andfurther amendments, is constituted by two different cycles (Fig. 2):the first one is known as Urban Driving Cycle (UDC), and the secondone is defined as Extra-Urban Driving Cycle (EUDC). In the UDC thevehicle is driven through 1013m at an average speed of 18.7 km h�1

during 195 s. This routine is repeated four times in a sequence,totalizing 4052 m in 780 s. The urban driving conditions are char-acterized by low speed, low engine load, and low exhaust gastemperature. By contrast, the EUDC, in the second part of the NEDC,accounts for extra-urban and high speed driving modes up to amaximum speed of 120 km h�1. The vehicle has an average speed of62.6 km h�1 and it takes 400 s to move through 6955 m. The entireNEDC covers a distance of 11,007m in a time period of 1180 s and atan average speed of 33.6 km h�1. Before the experiment the vehiclewas conditioned at an ambient temperature between 20 and 30 �Cfor at least 12 h. The NEDC’s speed profile is shown in Fig. 2.

The NEDC was repeated four times for each fuel blend and eachfirst replica was not considered in data analysis in order to mini-mize the impacts of the fuel change on the engine performance.

2.3. Exhaust flue gas sampling and analysis

Typically the sampling and analysis of regulated pollutantemissions from motor vehicles are performed in accordance to theEuropean regulation (Directive 70/220/EEC and further amend-ments), following the constant volume sampling technique. This

Table 2Fuel properties.

Parameter/unit B0 B7 B20 Test method

Density at 15 �C (kg m�3) 837.0 840.1 846.0 EN ISO 3675Viscosity at 40 �C (mm2 s�1) 2.430 2.845 2.980 EN ISO 3104Flash point (�C) >55 74.5 76.5 EN ISO 2719Water content (mg kg�1) <50 105 171 EN ISO 12937Calculated cetane index 51.8 51.9 52.1 EN ISO 4264FAME content [% (v/v)] <0.1 6.9 20.0 EN 14078Heating value (MJ kg�1) 45.598 45.146 44.418 ASTM D-240DistillationRecovered at 250 �C [% (v/v)] 36 34 27 EN ISO 3405Recovered at 350 �C [% (v/v)] 93 93 93 EN ISO 340595% recovered (�C) 361.6 359.5 357.1 EN ISO 3405

technique maintains a constant total flow rate of vehicle exhaustplus dilution air. With a constant volume sampling system, asexhaust flow increases, such as during heavy acceleration, thedilution air is automatically decreased and the sampling source isrepresentative of exhaust variations.

The constant volume sampling method has been used to sup-port vehicle emissions testing for over 25 years and the ‘bag’measurement of emissions is the key method that is used for leg-islative purposes (Randazzo and Sodré, 2011). Bag measurementsprovide a single figure for CO, CO2 and NOx emissions species forthe complete drive cycle, but have their own limitations, providingno information on the emission profile throughout the test. Thus, adifferent sampling methodology based on continuous on-lineexhaust gas composition measurements was adopted in the workpresented here; this methodology provides a time profile for O2,CO, CO2, NOx and VOC along the experimental test of the vehicle.

For sampling the exhaust gas an experimental apparatus, wherethe vehicle tail pipe is connected to a larger duct simulating a fluegas stack chimney, was implemented (Fig. 1). The sampling probesand particulate matter filters were introduced in the vertical duct ina sampling hole. The location of the sampling section is in accor-dance with the Portuguese Standard 2167:2007. The entire systemwas heated above 100 �C to prevent water vapour and organicscondensation, under the typical existing concentrations in exhaustgases, thus avoiding any interference with the measurements.Moreover, a heated filter was installed in the sampling probe toremove particulate compounds, protecting the flame ionizationdetector that measures VOC.

The set of measured parameters and the respective equipmentused in this experimental work is compiled in Table 3.

The monitoring of O2, CO, CO2, NO2, NO and total VOC concen-trations was carried out on-line and continuously (registeringperiod: a second forO2, CO, CO2,NO2,NOandaminute for totalVOC).The gas samplewas extractedand conducted to an infrared sensor tomeasure CO2 concentration and to electrochemical cells through aheated line, for the remaining gaseous compounds. Regarding PMmeasurement, a parallel sampler extracted the exhaust gas andforces it to pass through an impactor, which separates particles ac-cording to their diameter. The particles have been divided into threefractions, corresponding to diameters above 10 mm (1st filter), be-tween 2.5 mmand 10 mm(2nd filter) and less than 2.5 mm(3rdfilter).The impactor which contained quartz filters was kept at the tem-perature of the system (above 100 �C) to avoid condensation in thesampler pipe. The mass collected in the various filters was deter-mined gravimetrically, after a drying process. After gravimetricdetermination, filter punches were analysed by a thermo-opticaltransmission system in order to quantify the carbonaceous contentinto organic carbon and elemental carbon. Details of the analyticaltechnique are provided in (Alves et al., 2011). Finally, samples ofexhausted gas were collected using Tedlar bags in order to performVOC speciation analysis by gas chromatography according to themethodology described by Evtyugina et al. (2013).

3. Methodology

The principle of mass conservation was applied to perform twofundamental steps: (1) calculation of the mass and volumetric flowrate; and (2) calculation of the emission factors. The calculationswere based on the assumption of complete oxidation of thechemical elements that compose the fuel and that the combustionair was dry, namely, the mass ratio of humidity in air combustion(WVA) was inexistent. Furthermore, as the gaseous productsresulting from combustion include a diversified set of substances,only their major components (CO2, H2O, O2 and N2) were consid-ered for effects of global mass balance. In fact pollutants such as HC,

Fig. 1. Scheme of the experimental infrastructure.

Fig. 2. Speed profile of the New European Driving Cycle (NEDC).

Table 3Equipment used in experimental work.

Equipment Parameters Detection limit Response time (s) Resolution Accuracy Test method

Andersen control unit Dry gas meter e e 0.0001 <� 2% m.v. e

Hot Box Support and heating the filtersampling

e e e e ISO 23210:2009

Impactor and quartz filters PM10 and PM2.5 e e e e ISO 23210:2009Cold box Bubblers cooling in an ice bath e e e e EN 14790:2005Thermocouple Exhaust gas temperature e e 1 <�3 e

TESTO 350 XL (gas analyser) O2 0.1% <20 0.01% <0.2% m.v. EN 15259:2007CO 1 ppm <40 1 ppm <5% m.v.CO2 0.02% <10 0.01% <1.5% m.v.NO 1.8 ppm <30 1 ppm <10% m.v.NO2 0.5 ppm <40 0.1 ppm <2% m.v.

Bernath Atomic Model 3006Analyser (flame ionization detector)

VOC 0.4 ppm 3 0.2 ppm <5% Span EN 15259:2007EPA 25A

Balance Mettler (mod. AG285) Mass e e 0.1 mg �0.017 mg e

Balance Sartorius (PT 1200) Mass e e 0.1 g �0.058 gGas chromatograph VOC 0.4 ng e <� 7% m.v. e

Thermo-optical transmission system Elemental carbon/organic carbon 0.6 ppma 1 �2 g/filterb e

m.v. e measured value.a NDIR CO2 analyzer.b Accuracy based on TC variability on blank quartz filter.

M. Lopes et al. / Atmospheric Environment 84 (2014) 339e348342

Table 5Fuel consumption, mass air flow, and exhaust gas flow rates in mass and volumebasis, by fuel and for each driving cycle.

Fueltype

Drivingcycles

Fuel consumption(l$100 km�1)

Mass airflow(kg h�1)

Exhaust massflow (kg h�1)

Exhaustvolumetricflow(Nm3 h�1)

Range Average

B0 UDC 6.32e6.47 6.33 30.96 31.65 24.61EUDC 5.56e5.64 5.59 65.55 93.23 72.48NEDC 5.84e5.94 5.86 48.26 52.52 40.83

B7 UDC 6.35e6.48 6.44 32.22 32.35 25.14EUDC 5.56e5.67 5.61 64.78 94.36 73.34NEDC 5.89e5.97 5.92 48.50 53.37 41.48

B20 UDC 6.27e6.37 6.31 30.78 31.65 24.60EUDC 5.53e5.50 5.53 65.28 92.71 72.05NEDC 5.79e5.84 5.82 48.03 52.35 40.69

M. Lopes et al. / Atmospheric Environment 84 (2014) 339e348 343

H2, CO, NO, NO2, SO2, HCl, HF, and some organic micropollutants(polycyclic aromatic hydrocarbons, dioxins, furans, among others)have small effect on the total of exhaust emissions (Heywood,1988). The two steps are described in detail below.

3.1. Determination of mass and volumetric exhaust flow

Combustion flow was calculated by applying the principle ofmass conservation, through the analysis of the chemical reactionstranslating the combustion processes of diesel (Equation (1)) andbiodiesel (Equation (2)) fuels. The elemental composition of thefuels used in the experiments (%, m m�1), on dry basis, wasdetermined based on the analysis of the stoichiometry. The dataobtained are presented in Table 4.

C12H26 þ 18:5 O2 þ 18:5� 3:76 N2/12 CO2 þ 13 H2O

þ 69:56 N2 (1)

C19H34O2 þ 26:5 O2 þ 26:5� 3:76 N2/19 CO2 þ 17 H2O

þ 99:64 N2 (2)

Since the combustion process and its products are directlydependent of the existing air, it becomes indispensable to deter-mine the current oxygen requirements, dependent of the stoichio-metric requirement of oxygen that enables the complete oxidationof fuel. Thus, since the oxygen content of the combustion gases foreach fuel type was measured, values of excess of air were arbitrateduntil the value of the current oxygen requirements is obtained(about 70%). Having compiled the information described, the massflow of each combustion product (ṁgas i), expressed in ggas i h�1, wasobtained by applying Equation (3).

_mgas i ¼ ni �Mi � GF (3)

In Equation (3), ni is the elemental mass balance, in mol ofelement i by kg of dry fuel; Mi is the molar mass of product i, ing mol�1; and GF is the fuel consumption, in g h�1. The results foreach type of fuel examined are presented in Table 5. It should benoticed that the consumptions presented correspond to the meanvalue of the tests performed for each fuel, with the distinctionbetween the respective driving cycles, whereby the flows obtainedare presented as mean flows. By this way, the error associated withthe experimental work was reduced. With the same purpose, thefirst test of each fuel type was excluded, to eliminate errors asso-ciated to the adjustment of the engine to the fuel.

Once the mass flow of combustion products is obtained, thedetermination of the volumetric flow rate was based on the esti-mation of the densities of each product (ri, in kgm�3) and assumingideal conditions. The volumetric flow rates of exhaust (Gexh), inNm3 h�1, are presented in Table 5.

3.2. Determination of the emission factors

The emission factors (EF) were calculated taking into accountthe volumetric flow rate for each fuel type analysed and each

Table 4Stoichiometric elemental composition (% m m�1) of fuel, on dry basis.

Element Elemental composition (%)

Diesel Biodiesel

Carbon 5.314 5.799Oxygen 21.848 22.381Hydrogen 0.959 0.865Nitrogen 71.879 70.956P

100 100

driving cycle (UDC and EUDC), the velocity (v) and the pollutantconcentration emitted (C0i), on a dry basis (as expressed by Equa-tion (4)). Emission factors were then obtained for each pollutant,for each driving cycle and for each fuel type examined, expressed ing km�1.

EF ¼�Gexh � C0i � 10�3

�.v (4)

In order to establish comparison between the different fuelsanalysed, mass concentrations were corrected for standard condi-tions. This condition of specific reference includes the temperature(T0), the absolute pressure (P0), and a value to molar fraction ofoxygen (y00), which depends on the applications (Portuguese DecreeNo. 178/2003). Since the Portuguese Decree No. 677/2009, of June23, establishes the emission limit values applicable to combustionplants, especially on internal combustion engines, to an oxygencontent of 15%, this was the value used in the correction of oxygen.The acronyms T, P and y0 correspond, respectively, to the values oftemperature, pressure and molar fraction of oxygen measuredduring the tests. In these circumstances the concentration instandard conditions, C0i, expressed in mg Nm�3, was estimatedthrough Equation (5).

C0i ¼ Cmi �h�

0:21� y00�.

ð0:21� y0Þi��T=T0

���P0=P

�

(5)

4. Characterization of the test conditions

Table 5 shows the fuel consumption and the mass air flowmeasured as indicators of the engine’s behaviour during the trialscarried out, as well as the volumetric andmass flow rates of exhaustgases determined according to the methodology described in Sec-tion 3.

The fuel consumption and mass air flow are similar among thedifferent used fuel blends; therefore there was no noticeable effectof the use of biodiesel in the diesel engine operation.

Regarding the vehicle speed profile, all trials followed the ve-locity profile that characterizes the NEDC cycle, presenting aPearson’s correlation coefficient of 0.998. This value reveals astrong association between the standard and the experimentalprofiles, which allows the validation of the tests performed.

On the other hand, analysis of the oxygen content shows theconsistency of results, all tests varied in the range of 5.28 and16.71% of O2. Table 6 shows the minimum, maximum and alsomean ambient temperature on the laboratory during the experi-ments. Maintaining the temperature of the laboratory at the same

Table 6Ambient temperature of the experiments, for each fuel blend used.

Fuel Ambient temperature (�C)

Mean Minimum Maximum

B0 31.1 30.7 31.4B7 30.4 30.0 30.7B20 33.8 33.4 34.3

M. Lopes et al. / Atmospheric Environment 84 (2014) 339e348344

level during the experimental period is important to preventpossible effects on combustion/engine behaviour and emissionfactors as well. The maximum variation was 4.03 �C.

5. Results and discussion

The measurement of concentration allows the understanding ofthe complete profile for O2, CO, CO2 and NOx. However, theequipments used have a time response (Table 3) which must betaken into account during the data post-processing. In spite of theequipments were capable to make the measurement cycle showingobvious variations of the various pollutants as a function of thespeed in perfectly conditions, they took a little bit to take the first

Fig. 3. B20 profiles of speed and exhausts gases temperature (a)

value when tests began. To address the time response problem,both speed and concentration curveswere crossed in order to rejectthe first seconds of the concentration data series to coincide withthe both curves.

Since the concentration profiles from the tests were quiteconsistent, Fig. 3 only represents the observed concentration pro-files and the vehicle speed regarding the B20.

The O2 and CO2 contents vary oppositely throughout the test(Fig. 3b). Moreover the observed CO concentrations are low, belowthe detection limit of the equipment (Table 3), which means thatthe combustion process is close to complete. NOx (Fig. 3c) con-centrations were low during the UDC (1st part of the NEDC),increasing with both speed and exhaust gas temperature in theEUDC (2nd part of the NEDC), credited to the fact that NOx is pro-duced especially at high temperatures (Lupiáñez et al., 2013; Shaoet al., 2013). The concentration levels increase is especiallyobserved during the speeding up periods and declines in cruisespeed periods.

5.1. CO2

One of the main motivations for the use of biodiesel in thetransportation sector is the reduction of CO2 emissions. Despite

and measured concentrations of O2 and CO2 (b) and NOx (c).

M. Lopes et al. / Atmospheric Environment 84 (2014) 339e348 345

some authors (e.g. Xue et al., 2011) reporting a reduction of CO2emission when biodiesel is added to petroleum-based diesel, thecurrent experimental results show that CO2 emissions can slightlyincrease with the use of biodiesel blends (Fig. 4). The same resultswere obtained by Bakeas et al. (2011), Karavalakis et al. (2011), andFontaras et al. (2010).

Comparing the emission factors estimated for all tested fuelblends, B7 is the fuel with higher CO2 emissions and higher fuelconsumption (Table 5). On the other hand, B20 presents the lowerfuel consumption, but the emission factors under the NEDC(115.36 g km�1) are between pure diesel (113.71 g km�1) and B7blend (117.48 g km�1). These two factors could probably mean thatthe B20 blend leads to a more efficient and complete combustionthan B0 and B7.

5.2. CO

As indicated in Table 3, the detection limit of the equipmentused (TESTO 350 XL) is 1 ppm and the accuracy error of the analyseris 5% of the value measured. The high values measured werefounded for B7, nevertheless the CO concentrations in the exhaustgas were within or below the detection level of the monitoringequipment used. Taking this into account, it was not possible toconclude about CO emission behaviour using B0, B7 and B20.

5.3. NOx

Various nitrogen-based components are formed during thecombustion process on a diesel engine, in particular NO and NO2.The formation of NOx depends mainly on the oxygen available, thelocal combustion temperatures and the load conditions (Sun et al.,2010). The nitrogen oxides emission factors obtained by fuel typeand driving cycle are presented in Fig. 5.

Looking at the complete driving cycle, the NOx emissions arebelow the EURO 5 limit value for all blends (0.18 g km�1, ECRegulation 715/2007). Typically, the NOx produced by a combustionreaction on a diesel engine is about 98% NO (Sun et al., 2010).However, the experimental results point out a distribution of about50% of NO and 50% of NO2, which means that the combustionprocesses occurred in the presence of excessive O2, allowing theoxidation of NO to NO2 from the motor to the tail pipe.

B20 was the fuel with lower NOx emission factors (0.15 g$km�1

over NEDC) with a reduction of 10.8% and 11.4%, when compared toB0 and B7, respectively. Furthermore, the trend of NO emissions for

Fig. 4. CO2 emission factors by fuel type and driving cycle.

each fuel is similar to NOx. This can be explained by the reducedneed of air and fuel (see Table 5) of B20, since NO is mainly formedduring the combustion process, in other words, B20 promotes amore efficient combustion (as already mentioned in Section 5.1).

The exhaust gas temperatures of B20 and B0 are similar(109.1 �C and 109.0 �C for B0 and B20, respectively) and higher thanB7 (100.4 �C), which could explain the lower NO2 emissions asso-ciated to B7 over UDC and NEDC, due to NO2 being mainly formedby the Zeldovich mechanism.

Besides the results not displaying a clear trend between emis-sions and biodiesel blend, they point out a decreasing trend of NOx

emissions, mainly due to the increase of combustion efficiency withhigher mixture rates of biodiesel. The increase of combustion effi-ciency is probably due to the increase of the blend’s viscosity(biodiesel is more viscous than diesele see Table 2), which can playan important role in improving the lubrication of the injectionmetallic components of the engine.

5.4. Particulate matter

According to most studies performed regarding the impact ofbiodiesel on particulate matter emissions (e.g. Xue et al., 2011;Bakeas et al., 2011), the use of a biodiesel blend causes a reduc-tion in PM. However, these studies refer to vehicles with previoustechnology than the vehicle tested (EURO 5). As described inSection 2.1, the EURO 5 vehicles are equipped with diesel partic-ulate filter a system, which means that PM emissions can bereduced in 90% (Bergmann et al., 2009; Tente et al., 2011). Takingthis into consideration, the same filters were used in the fourreplicas of each fuel blend in an attempt to sample as much par-ticulate matter mass as possible. After, the filters were weighed inlaboratory, but the mass of the accumulated particulate matter inthe filters was below the detection limit and no conclusion couldbe taken concerning the PM emissions with the use of thedifferent biodiesel blends. Diesel particulate filter are not onlyeffective in removing larger particulate matter such as PM10, butalso effective in removing smaller particulate matter because allsize fractions were removed by this filters. This finding confirmsthat diesel particulate filter installed in modern diesel light vehi-cles are in fact highly efficient and emissions cannot be quantifiedby gravimetric methods. Thus, this methodology is inappropriateto quantify PM emissions in vehicles equipped with diesel par-ticulate filters.

Despite the low content of particles found in the filters, it waspossible to quantify the levels of total particulate carbon (Fig. 6)using a thermo-optical transmission system, including its specia-tion in organic carbon (OC) and elemental carbon (EC) for fineparticulate fractions (PM < 2.5).

The main carbonaceous content was concentrated in the finefraction of all experiments, and is dominated by organic com-pounds, The OC/EC ratio ranged between 3 and 6 in the fine frac-tion. A decrease in EF for total carbon is observed with an increaseof biofuel in the blend mixture. The emission factor of total par-ticulate carbon could be used like a lower limit of PM emissionfactor for these experiments.

5.5. VOC

As described in Section 2.3, two different kinds of measure-ments of VOC concentrations took place during the experiments:(1) through the flame ionization detector total VOC concentrationswere measured per minute; and (2) a sample of exhausted gaseswas collected into a bag during the third UDC and EUDC of eachNEDC in order to perform a VOC speciation analysis by gas

Fig. 5. NO, NO2 and NOx (NO þ NO2) emission factors by fuel type and driving cycle, and the emission limit value indicated by the EC Regulation 715/2007.

M. Lopes et al. / Atmospheric Environment 84 (2014) 339e348346

chromatography. Fig. 7a represents the total VOC emissions fromthe three fuels used.

Compared with pure diesel, the B7 fuel displays higher values oftotal VOC emissions (Fig. 7a), especially over the UDC, while the B20fuel presents similar values to B0. However, the comparing be-tween B7 and B20 fuels indicates that total VOC emissions decreasewith higher biodiesel rates. Lower emissions may result fromhigher cetane number and oxygen content for B20 fuels. Fuels withhigh cetane number can reduce ignition delay and help promotemore complete combustion, which could lead to reduction in hy-drocarbon emissions. In addition, higher oxygen content in B20 fuelhelps to combust completely and reduces emissions (Peng et al.,2008, 2012; Rounce et al., 2012).

Gas chromatography results (Fig. 7b) show that the set of VOCspecies and their concentrations change according to the fuel blendused. Sixteen different VOC species were found in B7 and B20,

Fig. 6. Coarse and fine fraction (EC and OC) of total carbon (TC) emission factor inPM10, for B0, B7 and B20, considering all the NEDC.

instead of the twelve presented on exhaust gases from experimentswith pure diesel. The set of dominant VOC (species with concen-tration above 50 ng m�3) regarding pure diesel is characterized bythe presence of benzene (25.9%), toluene (21.1%) and octane (18.1%).On the other hand the set of dominant VOC for B7 includes nonane(16.0%), benzene (13.7%), butanal (11.1%), m,p-xylene (10.6%) and 2-ethoxyethanol (8.9%). The highest total VOC emission factorobserved for B7 fuel may be associated with nonane and some ofthe oxygenated compounds that exhibited higher concentrationsthan the registered for the other two fuels. Even we cannot give afull explanation for the behaviour of total VOC emission factors forB7 fuel for UDC it seems that the answer could be related to thecompounds referred to above. Finally, for B20 the main VOC arebutanal (18.3%) and m,p-xylene (14.1%). The obtained results pointout that the concentration of the three main VOC species in exhaustgases from B0 (benzene, toluene and octane) decrease between 60and 80% if a B20 blend is used.

It is also interesting to verify that some VOC species may appearin exhaust gases if a biodiesel blend is used as fuel instead of purediesel (2-propanol, 1-butanol, 2-ethoxyethanol, a-pinene).

In accordance to Peng et al. (2012) the dominant VOC of purediesel engine exhausts have the highest chronic hazard quotientsand hazard indices than VOC from B20. Thus, the use of pure dieselis more injurious for human health than biodiesel blends, in termsof VOC emissions.

6. Conclusions

The influence of diesel/biodiesel blends on the fuel consumptionand the exhaust gas emissions patterns of a EURO 5 passengervehicle (technology from 2009 to 2014) was assessed. Experimentswere performed using a Renault Megane 1.5 dCi (2011), operatedover the New European Driving Cycle (NEDC) on a laboratorychassis dynamometer. Fuel blends containing 7% (B7) and 20%(B20) of biodiesel (84% soyabean/16% palm) in petroleum-baseddiesel were tested and compared with a 100% diesel fuel (B0).

Fig. 7. Total VOC emission factor (a), and concentration of some species of VOC, for B0, B7 and B20 (b).

M. Lopes et al. / Atmospheric Environment 84 (2014) 339e348 347

Despite the reduction of CO2 emissions as one main reason forthe use of biodiesel in road-transportation, the results of thisexperimental work show that CO2 emissions may slightly increasewith biodiesel blends. Compared to the pure diesel fuel, CO2emissions from the biodiesel blend revealed a slight increase, withB7 fuel presenting the higher emissions. The tests performed withB20 revealed a decrease in fuel consumption and a more efficientcombustion process. Nevertheless, CO2 emissions were higher thanthe emissions of the B0 tests.

The analysis of NOx within the set of fuels tested allows theconfirmation that B20 was the better blend in terms of emissionsand also combustion efficiency. The opposite was found with B7. Inthe combustion chamber, the NO emissions decrease in the pres-ence of B20, when compared to B0. On the other hand, after thecombustion, NO2 emissions increase with B20 and decrease withB7. This occurred mainly because B20 allows higher combustiontemperature (due to a better efficiency) than B7 and B0.

The obtained PM emission results were inconclusive concerningthe influence of biodiesel on PM emissions, since themass collectedin the filters (by gravimetric method) was below the detectionlimit.

The experiments performed show that total VOC emissions mayincrease with biodiesel blend ratios. However the set of VOC

species present on exhausted gases is highly dependent on the fuelblend used.

One of the central results of this experiment is that the use of B7may imply higher emissions than B0 and B20. In fact, B7 had a non-expectable behaviour regarding all the parameters that were takeninto account. Moreover, for all the studied pollutants and for all thereplicas executed, larger error bar for B7 were obtained. Probably,the variation on the temperature of exhausted gases founded to B7(100 �C by average) in relation to B0 and B20 (109 �C by average)may indicates that the combustion temperature was lower for B7than for other blends and then justify the odd behaviour of B7.Moreover, the higher fuel consumption and the mass air flow aswell as high CO2 and VOC emissions and lower NOx emissions for B7point out to the same direction, lower combustion temperature forthis blend. In sum, the analysis of the process, regarding B7, sug-gests that lower combustion temperature that may occur probablydestabilized the combustion and catalyst processes and thusincreasing the fuel consumption and CO2, CO, NOx and VOCemissions.

This experimental study contributes to a better characterizationof the emission factors of the vehicles using diesel/biodiesel blendsand to a better understanding of the impact of the use of this kind offuel on engine performance and pollutant emissions.

M. Lopes et al. / Atmospheric Environment 84 (2014) 339e348348

Acknowledgements

The authors acknowledge the financial support of project BIO-GAIR (PTDC/AAC-AMB/103866/2008; FCOMP-01-0124-FEDER-008587), supported in the scope of the Competitiveness FactorsThematic Operational Programme (COMPETE) of the CommunitySupport Framework III and by the European Community FundFEDER. An acknowledgement to the Portuguese ‘Ministério daCiência, da Tecnologia e do Ensino Superior’ for the Ph.D grant ofIsabel Ribeiro (SFRH/BD/60370/2009) and the post-doc grant ofAlexandra Monteiro (SFRH/BPD/63796/2009). The authors are alsograteful to PRIO Energy for providing the biodiesel for this study.Ole John Nielsen thanks the VillumKann Rasmussen Foundation forfinancial support.

References

Abd-Alla, G.H., 2002. Using exhaust gas recirculation in internal combustion en-gines: a review. Energy Convers. Manag. 43, 1027e1042.

ACAP e Associação Automóvel de Portugal (Portugal Automobile Association), 2011.Estatísticas Do Sector Automóvel 2010. Available at: http://www.iea.org (lastaccessed 02.07.12.).

ACEA e European Automobile Manufacturers Association, 2010. Diesel MarketHighly Developed in Europe. Available online at: http://www.acea.be (lastaccessed 16.06.12.).

Alves, C., Vicente, A., Nunes, T., Gonçalves, C., Fernandes, A.P., Mirante, F., Tarelho, L.,Sánchez de la Campa, A.M., Querol, X., Caseiro, A., Monteiro, C., Evtyugina, M.,Pio, C., 2011. Summer 2009 wildfires in Portugal: emission of trace gases andaerosol composition. Atmos. Environ. 45, 641e649.

Bakeas, E., Karavalakis, G., Stournas, S., 2011. Biodiesel emissions profile in moderndiesel vehicles. Part 1: effect of biodiesel origin on the criteria emissions. Sci.Total Environ. 409, 1670e1676.

Bergmann, M., Kirchner, U., Vogt, R., Benter, T., 2009. On-road and laboratoryinvestigation of low-level PM emissions of a modern diesel particulate filterequipped diesel passenger car. Atmos. Environ. 43, 1908e1916.

Bermúdez, V., Lujan, J.M., Pla, B., Linares, W.G., 2011. Comparative study of regulatedand unregulated gaseous emissions during NEDC in a light-duty diesel enginefuelled with Fischer Tropsch and biodiesel fuels. Biomass Bioenergy 35, 789e798.

Decree No. 178/2003. Decreto-lei n� 178/2003, Ministério das Cidades, Ordena-mento do Território e Ambiente, 5 de Agosto de 2013 (Ministries of cities,Planning and Environment, 5th August 2003).

Demirbas, A., 2009. Biofuels e Securing the Planet’s Future Energy Needs. Springer,Heidelberg, Germany, p. 335. ISBN 978-84882-010-4.

Evtyugina, M., Calvo, A., Nunes, T., Alves, C., Fernandes, P., Tarelho, L., Vicente, A.,Pio, C., 2013. VOC emissions of smouldering combustion from Mediterraneanwildfires in central Portugal. Atmos. Environ. 64, 339e348.

Fontaras, G., Kousoulidou, M., Karavalakis, G., Tzamkiozis, T., Pistikopoulos, P.,Ntziachristos, L., Bakeas, E., Stournas, S., Samaras, Z., 2010. Effects of low con-centration biodiesel blend application on modern passenger cars. Part 1:feedstock impact on regulated pollutants, fuel consumption and particleemissions. Environ. Pollut. 158, 1451e1460.

Gaffney, J.S., Marley, N.A., 2009. The impacts of combustion emissions on air qualityand climate e from coal to biofuels and beyond. Atmos. Environ. 43, 23e36.

Gupta, R.B., Demirbas, A., 2010. Gasoline, Diesel and Etanol Bioduels from Grassesand Plants. Cambridge University Press, New York, USA, ISBN 978-0-521-76399-8, 230 pp.

Heywood, J.B., 1988. Internal Combustion Engine Fundamentals. McGraw-Hill, NewYork, USA, 930 pp.

IEA e International Energy Agency, 2011. Key World Energy STATISTICS. Availableat: http://www.iea.org (last accessed 16.06.12.).

IPCC e Intergovernmental Panel on Climate Change, 2007. Climate change 2007 e

the physical science basis. In: Contribution of Working Group I to the FourthAssessment Report of the Intergovernmental Panel on Climate Change. Cam-bridge University Press, Cambridge, United Kingdom and New York, NY, USA,p. 996.

Karavalakis, G., Stournas, S., Bakeas, E., 2009. Effects of diesel/biodiesel blends onregulated and unregulated pollutants from a passenger vehicle operated overthe European and the Athens driving cycles. Atmos. Environ. 43, 1745e1752.

Karavalakis, G., Bakeas, E., Fontaras, G., Stournas, S., 2011. Effect of biodiesel originon regulated and particle-bound PAH (polycyclic aromatic hydrocarbon)emissions from a Euro 4 passenger car. Energy 36, 5328e5337.

Kaspar, J., Fornasiero, P., Hickey, N., 2003. Automotive catalytic converters: currentstatus and some perspectives. Catalysis-Today 77 (4), 419e449.

Kousoulidou, M., Ntziachristos, L., Fontaras, G., Martini, G., Dilara, P., Samaras, Z.,2012. Impact of biodiesel application at various blending ratios on passengercars of different fueling technologies. Fuel 98, 88e94.

Krahl, J., Baum, K., Hackbarth, U., Jeberien, H.E., Munack, A., Schutt, C., Schröder, O.,Walter, N., Bünger, J., Müller, M.M., Weigel, A., 2001. Gaseous compounds, ozoneprecursors, particle number and particle size distributions, and mutagenic ef-fects due to biodiesel. Trans. Am. Soc. Automot. Eng. 44, 179e191.

Lapuerta, M., Armas, O., Rodríguez-Fernández, J., 2008. Effect of biodiesel fuels ondiesel engine emissions. Progr. Energy Combust. Sci. 34, 198e223.

Lupiáñez, C., Guedea, I., Bolea, I., Díez, L.I., Romeo, L.M., 2013. Experimental study ofSO2 and NOx emissions in fluidized bed oxy-fuel combustion. Fuel Process.Technol. 106, 587e594.

McCormick, R.L., Williams, A., Ireland, J., Brimhall, M., Hayes, R.R., 2006. Effects ofBiodiesel Blends on Vehicle Emissions. Milestone Report, NRLE/MP, 4055e540.

Monteiro, A., Miranda, A.I., Borrego, C., Vautard, R., 2007. Air quality assessment forPortugal. Sci. Total Environ. 373, 22e31.

Peng, C.Y., Yang, H.H., Lan, C.H., Chien, S.M., 2008. Effects of the biodiesel blend fuelon aldehyde emissions from diesel engine exhaust. Atmos. Environ. 42 (5), 15e906.

Peng, C.Y., Yang, H.H., Lan, C.H., Yang, C.Y., 2012. Effects of biodiesel blend fuel onvolatile organic compound (VOC) emissions from diesel engine exhaust.Biomass Bioenergy 36, 106e196.

Randazzo, M., Sodré, J., 2011. Exhaust emissions from a diesel powered vehiclefuelled by soybean biodiesel blends (B3eB20) with ethanol as an additive(B20E2eB20E5). Fuel 90, 103e198.

Ross, Z., Kheirbek, I., Clougherty, J.E., Ito, K., Matte, T., Markowitz, S., Eisl, H., 2011.Noise, air pollutants and traffic: continuous measurement and correlation at ahigh-traffic location in New York City. Environ. Res. 111, 1054e1063.

Rounce, P., Tsolakis, A., York, A.P.E., 2012. Speciation of particulate matter and hy-drocarbon emissions from biodiesel combustion and its reduction by aftertreatment. Fuel 96, 90e99.

Serrano, L., Carreira, V., Câmara, R., Gameiro da Silva, M., 2011. On-road performancecomparison between two cars consuming petrodiesel and biodiesel. In: 4thInternational Congress on Energy and Environment Engineering and Manage-ment, Mérida e Spain, p. 6.

Shao, L.M., Fan, S.S., Zhang, H., Yao, Q.S., He, P.J., 2013. SO2 and NOx emissions fromsludge combustion in a CO2/O2 atmosphere. Fuel 109, 178e183.

Sun, J., Caton, J.A., Jacobs, T.J., 2010. Oxides of nitrogen emissions from biodiesel-fuelled diesel engines. Progress Energy Combust. Sci. 36, 677e695.

Taylor, G., 2008. Biofuels and the biorefinery concept. Energy Policy 36 (12), 4406e4409.

Tente, H., Gomes, P., Ferreira, F., Amorim, J.H., Cascão, P., Miranda, A.I., Nogueira, L.,Sousa, S., 2011. Evaluating the efficiency of diesel particulate filters in high-dutyvehicles: field operational testing in Portugal. Atmos. Environ. 45, 2623e2629.

Vestreng, V., Ntziachristos, L., Semb, A., Reis, S., Isaksen, I.S.A., Tarrasón, L., 2009.Evolution of NOx emissions in Europe with focus on road transport controlmeasures. Atmos. Chem. Phys. 9, 1503e1520.

Xue, J., Grift, T.E., Hansena, A.C., 2011. Effect of biodiesel on engine performancesand emissions. Renew. Sustain. Energy Rev. 15, 1098e1116.