Is Clean Diesel an Oxymoron?

H. Christopher Freyfrey@ncsu.edu

Department of Civil, Construction, and Environmental Engineering

North Carolina State UniversityRaleigh, NC 27695

NC BREATHE ConferenceApril 8, 2016Charlotte, NC

Topics• Diesel Engines• Emission Standards• Emissions and Air

Quality Trends• Technologies• Real-World Emissions

– On-Road – Non-Road

2

Diesel Engines

• Compression Ignited• High pressure ratio• Higher thermal efficiency than gasoline engines• Excess air• Relatively low emissions of products of incomplete

combustion:– Carbon monoxide– Hydrocarbons

• Relatively high engine-out emissions of nitrogen oxides (NOx):

– Nitric oxide (NO)– Nitrogen dioxide (NO2)

• Relatively high engine-out particulate matter (PM) emissions

Vehicles in the U.S.

• Highway (2013) Total: 255,876,822Light Duty: 236,010,230*Motorcycle 8,404,687Truck – single 8,126,007Truck – combo 2,471,349Bus 864,549

• Non-Road Freight Loco. 25,033Amtrak Loco. 418Construction (examples)

Excavators: 109,000Rubber tire loaders 133,000Backhoes 323,000

*3.1% of the light duty vehicle fleet is diesel

U.S. Heavy Duty Vehicle NOx and PM Emission Standards: 1998 - present

Emission Standards for Diesel Vehicles

• Light Duty: Same as for Gasoline Vehicles• Heavy Duty On-Road (typical approaches)

–Tier 1: Engine design–Tier 2: Exhaust Gas Recirculation (EGR)–Tier 3: EGR, Diesel Oxidation Catalyst (DOC)

+ Diesel Particulate Filter (DPF)–Tier 4: EGR + Selective Catalytic Reduction,

DOC + DPF• Diesel Non-Road

–Similar strategy, standards differ by engine size

Exhaust Gas Recirculation

Exhaust gas lowers the peak flame temperature, thereby reducing the rate of NOx production.

Truck Emission Controls Required Under “Tier 4” Standards: Diesel Particulate Filters

Diesel Particle Filter Regeneration

• Passive regeneration»Catalyze oxidation of carbon»Catalyze oxidation of NO to NO2, followed by

NO2 oxidation of carbon »Requires sufficiently high exhaust temperature

• Active regeneration–Heat the DPF with an external energy source

»Unburned fuel from engine»Fuel injected into exhaust gas»Electric heating

Heavy Duty Vehicle NOx Control

Fuel Quality Regulations

U.S. National Emission Inventory: Nitrogen Oxides

0

5,000

10,000

15,000

20,000

25,000

30,00020

0220

03

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

Annu

al T

ons

NO

x

Year

Highway VehiclesNon-Road VehiclesElectric UtilitiesIndustrial CombustionOther

U.S. National Emission Inventory: Primary PM2.5

0

500

1,000

1,500

2,000

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

Annu

al T

ons

PM2.

5

Year

Highway VehiclesNon-Road VehiclesElectric UtilitiesIndustrial CombustionOther

U.S. National Air Quality Trends: Nitrogen Dioxide

U.S. National Air Quality Trends: Ozone

U.S. National Air Quality Trends: PM2.5

Proposed Heavy Duty Vehicle Fuel Economy Standard

Technology Demonstration Programs:EPA “SmartWay” for Heavy Duty Trucks

Examples of Real-World Field Studies to Evaluate Diesel Emissions

• Reducing extended idling emissions• Evaluation of in-use effectiveness of emission

controls–Combination trucks–Vocational trucks (e.g., refuse trucks)–Nonroad construction equipment

• Biodiesel• Engine rebuild• Operator behavior

Long-Haul Sleeper Cab Trucks in the US• Approximately 680,000

long-haul sleeper cab trucks

• Rest stops required by Federal Hours of Service (HOS) regulations

• Base engine idling to provide “hotel” services

• Long-haul truck idle hours are estimated to range from 1,460 to 1,800 hours annually

Source: Volvo Trucks North America http://www.volvo.com/trucks/na/en-us

• Freight truck idling is estimated to consume 7% of freight truck fuel

Auxiliary Power Units

• Auxiliary power units (APUs) :

– Small diesel engine-generator

– Power for electrical air conditioning, heating, and auxiliary loads

Source: Mechron Power Systems http://www.ccslightning.com/

Study Methodology10 Fleet-A Trucks

With APU-A With APU-B

Data Acquisition System

10 Fleet-B Trucks

With APU-A With APU-B

Average In-service time: 11,300 hours (as of 2/29/07)

Average In-service time: 8,500 hours (as of 2/29/07)

Combined Multi-Monthly Route Map for 20 Field Trucks

0

50

100

150

200

250

300

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Truck Number

Annu

aliz

ed N

O E

mis

sion

(kg/

yr)

.

Base Engine Scenario Actual Scenario

NOx Emissions During Stops

Fleet A

Fleet B

Avoided NO emissions:For Fleet A: (Average: 48%; Range: 16-77%)For Fleet B: (Average: 12%; Range: 0.5-45%) Through 2/29/2008

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InstrumentationTest Truck

Exhaust Sampling Probes

PEMS

PEMS Connections

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Measured Trucks

a 2010 model year Truck 0121 is Mack. All other trucks are International.b DOC = Diesel Oxidation Catalyst; DPF = Diesel Particulate Filter;

EGR = Exhaust Gas Recirculation; SCR = Selective Catalytic Reduction

Trucka YearOdom. (miles)

ChassisModel

EngineDisp.(L)

EngineModel

HP Emissions Controlb

5715 1999 303,744 2574 6X4 10.8 ISM-370 370 -

6415 2005 235,202 9400I 6X4 15.0 ISX-500 500 EGR

6667 2007 61,008 9200I 15.0 ISX-500 500 EGR, DOC, DPF

0009 2009 72,831 9200I 15.0 ISX-500 500 EGR, DOC, DPF

0121 2010 29,229 CHU613 12.8MP8-445C

445 EGR, DOC, DPF, SCR

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Routes forDelivery of Highway Maintenance Supplies

N. WILKESBORO

CASTLE HAYNE

CLINTON

4

BURGAW

RALEIGH

1GREENSBORO HERTFORD

MANNS HARBOR3

SELMA

WILSON

5

#

WINSTON-SALEM

Route ID Number

NORTH CAROLINA

1,2

28

0

20

40

60

80

100

120

5715 6415 6667 0009 0121

NO

x(g

/gal

)

Truck Number

HighwayArterial

Comparison of Trucks: Fuel-Based NO Emission Rates

1999 2005 2007 2009 2010

Fuel-Based Emission Rates Similar Between “Bounding” Cycles

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0

0.1

0.2

0.3

0.4

0.5

0.6

5715 6415 6667 0009 0121

PM "

Opa

city

" (g

/gal

)

Truck Number

HighwayArterial

Comparison of Technologies: PM

PM is estimated using laser light scattering. These results are not intended as accurate emission rates, but rather to indicate relative differences.

1999 2005 2007 2009 2010

Types of Measured Refuse Trucks

Front-Loader: Diesel (6) Roll-Off: Diesel (6)

Side-Loader: Diesel (6)Side-Loader: CNG (3)

Front-Loader: CNG (3)

Instrumentation

Portable Emissions Meas. Sys. (PEMS)

Engine Control Unit (ECU) Readout

Exhaust Probes

GPS units

Route of Roll-off 3

170 miles7 cans

52 tons

Selective Catalytic Reduction Effectiveness

• The two Roll-Off Trucks with SCR had cycle average NO emission rates 87 percent lower than that of the four Roll-Off Trucks without SCR.

• The one Side-Loader Truck with SCR had cycle average NO emission rate 93 percent lower than the five trucks without SCR.

Diesel Particle Filter Effectiveness

• Of the diesel trucks, 3 front-loaders, 2 roll-offs, and 4 side-loaders had DPF

• Front-loaders: 98% average PM reduction• Roll-offs: 96% average PM reduction• Side-loaders:

– Overall: 88% average PM reduction– One 2008 DPF had just been serviced and apparently

was not working well: 64% PM reduction– Another 2008 DPF averaged 88% PM reduction– The 2010 and 2012 DPFs averaged 99% PM reduction

Field Data Collection for Dump Trucks

Study Design for Dump Truck Field Measurements

Single – Tier 1

Single – Tier 2

Tandem – Tier 1

Tandem – Tier 2

Vehicle Type Number Tested

4

4

2

2

All vehicles are part of NCDOT Division 5

Dump Truck Study Region:Wake County, North Carolina

Field Measurement of 8 Cement Mixers: B20 vs. Petroleum Diesel

• Four cement mixers measured in Atlanta, GA• Four measured in Vancouver, British

Columbia, Canada

Example: Installation of the PEMS on Construction Vehicles

• Study Location : Division 4 (Nash County) and Division 5 (Wake County)• Data Collection Scheduling

– 15 Tests with Petroleum Diesel and 15 Tests with B20 Biodiesel– Based on Regular NCDOT Duty Schedule

Overview of Study Design for Field Measurement

Vehicle TypeNumber of Vehicles Tested

Tier 0 Tier 1 Tier 2 Tier 3

Backhoes 1 2 2

Front-End Loaders 3 1

Motor Graders 2 2 1 1

Biodiesel vs. Diesel: Results from Real-World Tests of 35 Vehicles

a NO emissions were corrected based on ambient temperature and humidity

Type Vehicle NO a Opacity HC CO

Onroad

Dump Truck (12) -10 -10 -21 -11

Cement Mixer (8) -0.25 -20 -27 -27

Average -5.1 -15 -24 -19

Nonroad

Backhoe (5) -4.1 -17 -27 -17

Front-End Loader (4) -1.0 -19 -35 -42

Motor Grader (6) -0.16 -18 -17 -17

Average -1.8 -18 -26 -25

Overall (35) -3.5 -16 -25 -22

Emissions Reductions for Higher Tier vs. Lower Tier

Vehicle Engine Tiers NO(as NO2)a

Opacity-based PM HC CO

BackhoeTier 1 vs Tier 0 -7.0 0 -36 -49

Tier 2 vs Tier 0 -8.0 -48 -46 -86

Tier 2 vs Tier 1 -1.0 -48 -15 -72Front-End

Loader Tier 2 vs Tier 1 -23 -15 -57 -23

Motor Grader

Tier 1 vs Tier 0 -18 -15 -3.8 -51

Tier 2 vs Tier 0 -25 -37 -33 -60

Tier 3 vs Tier 0 -49 -42 -63 -74

Tier 2 vs Tier 1 -8.9 -26 -30 -18

Tier 3 vs Tier 1 -39 -31 -61 -47

Tier 3 vs Tier 2 -33 -6.8 -48 -35

a NO emissions were corrected based on the ambient temperature and humidityb This results are based on the average of two fuels

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B20 and B35 - Rubber Tire Loaders

1. Scoop Material

4. Load Truck

2. Carry Material

3. Lift Bucket

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NOx Emission Rate (g/gal)

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PM Emission Rate (g/gal)

Effect of Engine Rebuild

Before Rebuild – Spring 2008

Engine Rebuild

During Rebuild – Summer 2009

Engine Rebuild

After Rebuild – Fall 2009

Railyard and Dynamometer Test Results: Prime Mover Engine NO Emission Rate

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Biodiesel: Measured Locomotives

Three locomotives, each with an EMD12-710 Prime Mover Engine: 2-stroke, 12-cylinder, 140 L, 3000 hp

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AMTRAK Piedmont Route

Distance: 173 milesTravel time (RGH CLT): 3 hr, 15 minSpeed: 79 mph (max), 55 mph (avg)

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Portable Emissions Measurement System

Axion system by Clean Air Technologies

International, Inc.

• Non-dispersive infrared (NDIR) for CO2, CO, HC

• Electrochemical sensor for NO, O2

• Light scattering particulate matter measurement

53

Bottom Line Comparison of Soy-Based Biodiesel Blends with ULSD

Fuel NOx HC CO PM

B10 vs. ULSD + 10(0.44)

- 35(0.03)

- 6(0.77)

- 4(0.77)

B20 vs. ULSD + 6(0.60)

- 53(<0.01)

- 38(0.02)

- 23(0.09)

B40 vs. ULSD + 21(0.15)

- 39(0.04)

- 27(0.04)

- 17(0.10)

Difference in Cycle Average Emission Rates for Soy-Based Biodiesel Blends Versus Ultra Low Sulfur Diesel (ULSD) Based on Average Over-the-Rail Results for Three In-Use Locomotives

Values in parentheses are p-values of pairwise t-tests

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Operator and Locomotive NOx EmissionsTrip Total NOx Emissions for Six Engineers on the Piedmont Route Using Locomotive NC 1893 Emission Rates

Avg. NOx Emiss. (kg)Lowest to Highest

1 Engineer D (25.8)2 Engineer F (27.3)3 Engineer C (27.6)4 Engineer B (30.3)T5 Engineer A (31.7)T5 Engineer E (31.7)

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Operator and Locomotive PM EmissionsTrip Total PM Emissions for Six Engineers on the Piedmont Route Using Locomotive NC 1893 Emission Rates

Avg. PM Emiss. (kg)Lowest to Highest

1 Engineer C (1.12)2 Engineer D (1.15)3 Engineer F (1.24)4 Engineer E (1.38)5 Engineer B (1.40)6 Engineer A (1.42)

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Summary

• Real-world emissions from in-use diesels are decreasing in the U.S.

• Biodiesel can help reduce emissions from older vehicles• Advanced emission controls appear to be working and are

effective• Results may be sensitive to duty cycle and operator

behavior• Some design issues to be worked out• Fleet turnover will lead to lower in-use emissions• Long-term durability of controls needs to be monitored

Transportation, Energy, Emissions