(Bio) Fuels Emissions

Jim Dunsheejdunshee uvm edu

Transportation Air Quality Lab

to

NR 285/TRC 295Guest Lecture30-OCT-2015

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Relevance of Vehicle Emissions: Health

Image Source: epa.gov

3Image Source: US Chamber of Commerce (2015)

Substantial emissions reductions in some regions….but pollution does not follow geopolitical boundaries

Relevance of Vehicle Emissions: Macroscale

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VT Air Quality

Image Source: alg.umbc.eduImage Source: www.anr.state.vt.us

5Image Source: Paul Boulter (2012)

Relevance of Vehicle Emissions: Microscale

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Regulation (EPA & States):• National Ambient Air Quality Standards• Clean Air Act: 6 Criteria Pollutants• Nonattainment affects transportation funding

• Emissions Standards• By vehicle class

• Fuel Standards

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Chassis Dynamometer Lab

Image Source: Britt Holmén

Drive CyclesSteady-State

Transient

8 Image Source: dieselnet.com

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Image Source: The New York Times (October 22, 2015)

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Damage?

Distribution of estimated actual excess VW light duty diesel vehicle NOx emissions summed over 2008 through 2015 (kg km−2). The median value of emissions is used for each year. Emission density peaks at 446 kg km−2. (Barret et al., 2015)

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Real-world Emissions Testing

Image Source: dieselnet.com

Transportation Air Quality Modeling

Vehicle EmissionsModel

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Effect of new transportation system?Effect of new engine technology?Effect of new fuel type?

Air PollutionDispersion Model

Health Effects Model

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Important Factors for Vehicle Emissions

• Vehicle type (light vs. heavy-duty, gasoline vs. diesel, new vs. old)• Vehicle activity (drive cycle)• Emissions control technology• Ambient conditions (temp, humidity)• Fuel type/properties

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How do fuel propertiesaffect vehicle emissions?

O2

N2

Emission Chemical FormulaSoot CCarbon Monoxide COCarbon Dioxide CO2

Hydrocarbons CxHy

Oxides of Nitrogen NOx

+ Many More!

Fuel Chemical FormulaMethane CH4

Propane C3H8

Gasoline C8H18 (octane)Diesel C16H34 (cetane)Methanol CH3OHEthanol C2H5OHBiodiesel C19H34O2 (methyl linoleate)

Stoichiometric(Complete) Combustion

IncompleteCombustion

Image Source: Wikipedia

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Diesel Properties

Image Source: criticalfueltech.com

Medium petroleum distillates: C8 – C21

Ultra-Low Sulfur Diesel (ULSD):Naturally occurring sulfur (a lubrication agent)reduced to 15ppm = less soot formation

~75% Alkanes ~25%

May result in toxicaromatic emissions

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Biodiesel Properties

Stability = Less Oxidation

Image Source: themunicipal.com

Image Source: evansworkout.com

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Fatty Acid Methyl Esters (FAMEs)

Potential to reduce PM through complete combustion and soot oxidation:• Oxygen content of molecule• Absence of sulfur• Advanced start of combustion/injection• Absence of aromatic compounds• Lower final boiling point (compared to petrodiesel)

(Lapuerta et al., 2007)

Image Source: biofuelsystems.com/biodiesel-chemistry

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Is there an optimal feedstock and blend?• Commonly used at B20 or less• (≤20% biodiesel by volume)

• Desirability of each blend may vary by:• Ambient conditions (cold temperature)• Engine operating conditions or control strategy• Emissions produced & emissions control technology

Image Source: Wikipedia

Key

19Image Source: pollution.ucr.edu/criteriapollutants.html

breckpollution.weebly.com/health-effects.html

EPA Criteria Air Pollutants

C

O

P

N

S

Pb

soot

NOx

HC

CO

Tailpipe Emissions

Gasoline Engines Diesel Engines

NOx

HC

CO

After Jeffrey B. Burl and Duane AbataMichigan Tech University

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Spark vs. Compression Ignition Engine Emissions

Image Source: dieselnet.com

Diesel produces substantiallymore PM than gasoline

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Engine CyclesGasoline - Otto Cycle• Spark Ignition (SI)• Homogeneous combustion• Burns “rich”

• Air-fuel ratio < stoichiometric

Diesel - Diesel Cycle• Compression Ignition (CI)• Heterogeneous combustion• Burns “lean”

• Air-fuel ratio > stoichiometric

Image Source: Reactive Flow Modeling Laboratory (rfml.kaust.edu.sa)

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Heterogeneous vs. Homogenous Combustion

Image Source: https://youtu.be/_gqO3ncLfRg

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Cycle EfficienciesDiesel engines generally more efficient than gasoline due to: • Higher Compression Ratio (compressed air in cylinder)

• Higher Temperature Combustion (high pressure)

Image Source:Lyes KADEM [Thermodynamics II] 2007Concordia University

Fuel Properties and CombustionGasoline• Mixture of alkanes• C4-C12 (light distillates)

• Combustion rating indexed by octane

Diesel• Mixture of alkanes• C8-C21(medium distillates)

• Combustion rating indexed by cetane

Energy density:~32-34.8MJ/L

Energy density:~40.3MJ/L

Sources: 1998 W. G. Nichols - Chilton's Easy Car Care (www.procarcare.com); Alternative Fuels Data Center (www.afdc.energy.gov) 25

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Diesel PM/NOx TradeoffDiffusion Flame Combustion

Oxidation• Decreases soot (PM)• Increases NOx

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Diesel Tech. Effect on Diesel Market

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Diesel less popular in US than Europe

Subsidized fuel prices make less efficient, cheaper gasoline vehicles more appealing

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Diesel Exhaust & Health

“Diesel fumes cause lung cancer, the World Health Organization (WHO) declared Tuesday, and experts said

they were more carcinogenic than secondhand cigarette smoke”.- The New York Times, June 2012

“The health effects of [particulate matter] are

well documented. There is no evidence of a safe level of exposure or a threshold below which no adverse health effects occur”.- WHO, 2013

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Emissions Benefits of Biodiesel

• Renewable “drop in” fuel

(U.S. EPA 2002a) Data for heavy-duty engines and vehicles

B100Energy Density:~10-20% lowerthan diesel Fuel Econ & Power ~10% lower

Emissions Factors = Amount of Pollutant/Activitye.g., grams/mile

Image Source: duqlawblogs.org

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Variation in Evidence for PM

(Giakoumis et al., 2012)

Increases Decreases Both*

1 4 5

* Reported results vary by biodiesel feedstock and drive cycle, including both increases and decreases

Light-duty diesel studies:

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Biodiesel PM Health Effects• Soybean B20 exhaust PM caused 20-30% more

inflammation in mice cells compared to B00. (Fukagawa et al., 2013)

• Soybean B50 and B100 biodiesel PM promoted more cardiovascular alterations and pulmonary and systemic inflammation in mice compared to B00. (Brito et al., 2010)

• Cytotoxic effects of biodiesel from rapeseed methyl ester (RME) emissions were greater than those of diesel fuel. (Bunger et al., 2000)

Biodiesel PM: Ultrafine Particles

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BiodieselDiesel

Image Source: Tyler Feralio

Diesel PM Composition

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airalliancehouston.org

PAHs: Polycyclic aromatic hydrocarbons

astrochem.org

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Particulate Matter (PM)“A complex mixture of extremely small

particles and liquid droplets” (US EPA)

PM10 PM2.5

Image Source: ciese.org

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PM & Health: Smaller is Worse

• Class 1 Carcinogen• No evidence of safe exposure level(WHO, 2013)

Image Source: alencorp.com

Major Sources: Vehicles

µg/m³

37Image Source: epi.yale.edu

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Diesel Particulate Matter (DPM)

Product of unburned hydrocarbonsSolid, elemental carbon cores (i.e., soot)

Gas-phase hydrocarbons (organic carbon) nucleate to form particles….

… or adsorb to sootSEM image of DPM (Boehmann et al., 1999)

Image Source: Twigg & Phillips, 2009

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Particle Size & Lung Deposition

After D. Kittelson 1998

The human lungs cannot easily reject ultrafine particles!

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PM MeasurementGravimetric Method

Operational Definition:“mass collected on a filter” under specified conditions(Swanson et al., 2012)

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TAQ Lab Study• Ultra Low Sulfur Diesel (ULSD)• Two Biodiesel Feedstocks• From waste vegetable oil (WVO) & soy oil (SOY)

• BXX% Blends: B0, B10, B20, B50, B100

0% 100%

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Results: PM

N = 3 tests per blendError bars = ±1StDev

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Fuel Consumption

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Fuel Injection (According to ECM)

Fuel Injection Clip

Fuel Injection by Temperature

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Bannister et al. (2010)

Biodiesel = less energy/powerLower exhaust gas temps?

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Low exhaust temps during beginning of NEDC test cycle

Temperature Effects on Emissions

Still a NOx/PM trade-off

Bielaczyc et al. (2009)

Q&A