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Emissions of Toxic Pollutants from Compressed Natural Gas and Ultra-low

Sulfur Diesel - Fueled Transit Buses

Norman Y. Kado , Robert A. Okamoto , Paul A. Kuzmicky, Reiko Kobayashi , Alberto Ayala , Michael E. Gebel, Paul L. Rieger , Christine Maddox , and Leo Zafonte

Overall Objective

Investigate the regulated and toxic pollutant emissions from heavy-duty vehicles with and without control technologies.

Project Aims

• Investigate toxic emissions for CNG and ULSD-fueled heavy duty diesel vehicles

• Investigate the effect of after-treatment control technologies on emissions

• Investigate the effect of test cycles on emission rates

• Investigate ultrafine PM emissions

Project Notes

• Study is a “snap-shot” of the fleet and not a fleet average

Research Team

• ARB – Research Div, Stationary Source Div., Mobile Source Control Div., Monitoring Laboratory Div. & CAVTC.

• Dept. Environmental Toxicology, UC Davis; Dept. Environmental Engineering, UC Davis.

Contributing:

• South Coast AQMD, UCLA

Experimental Design

Gaseous PM - Toxics VP - Toxics

Chemical

Emissions

Bioassay BioassayChemicalChemical

Vehicle Configurations

CNG w/ OC

CNG no OC

Diesel w/ DPF

Diesel w/ OC

Phase 1b(2002)

Phase 1a(2001)

Configuration

CNG00 CNG01

Vehicles and After-Treatments

CNGOC (1b)Cummins-Westport C-Gas Plus

2001CNG 01

CNGNone (1a & 1b)OC (1b)

DDC-S50G2000CNG 00

ULSDDOC (1a)OC-DPF (1a)

DDC-S501998Diesel

FuelAfter-Treatment(Study)

Engine Make

Model YrVehicle

Catalyzed Diesel Paticulate Filter (DPF) for DDC 50 Diesel (Johnson-Matthey, Inc)

Oxidative Catalyst for CNG DDC S50G Engine

Fuels

• Ultra-Low Sulfur Diesel (ULSD)

• < 15 ppm sulfur

• Compressed Natural Gas (CNG)

• Methane (mole %): > 88%

Measurements Phases 1a & 1b

• Regulated pollutants (TPM, THC/NMHC, NOx, NO2, CO, CO2)

• On-site, VOC-GC analyses c matching off-site analyses

• Elemental/Organic Carbon

• Elements

• PM size-segregated mass (1a only), PM number & size

Toxic Pollutant Measurements

• Polycyclic Aromatic Hydrocarbons (PAHs)

• Carbonyls, BTEX, 1,3 Butadiene

• Bioassay - mutagenicity

Sampling

Ce ntra l Busine ss District (CBD) Cycle

0

5

10

15

20

25

1 30 59 88 117 146 175 204 233 262 291 320 349 378 407 436 465 494 523 552

Tim e (s e conds )

Spee

d (m

ph)

Central Business District Cycle

PM Emissions

0

10

20

30

40

50

D ie s e l (O C ) D ie s e l (D P F ) C N G .0 0 C N G .0 0 (O C ) C N G .0 1 (O C )

Ve hicle Configuration

Em

issi

on

s (m

g/m

ile)

119+/- 7

PM Emissions – CBD

NOx Emissions – CBDN Ox Emissions

0

10

20

30

40

Dies e l (OC ) Dies e l (DP F ) C NG .0 0 C NG .0 0 (OC ) C NG .0 1 (OC )

Ve hicle Configuration

Em

issi

on

s (g

/mile

) Total NOx NO2

CO Emissions - CBD

CO Emissions

0

4

8

12

Diesel (OC) Diesel (DPF) CNG.0 0 CNG.0 0 (OC) CNG.0 1(OC)

Vehicle Configuration

Emis

sion

s (m

g/m

ile)

TARGET PAHS

Particle Assciated PAHsBenzo[ghi]peryleneDibenz[ah]anthraceneIndeno[1,2,3-cd]pryenePeryleneBenzo[a]pyreneBenzo[e]pyreneBenzo[k]fluorantheneBenzo[b]fluorantheneChryseneBenz[a]Anthracene

Semi-Volatile PAHsPyreneFluorantheneMethyl PhenanthreneAnthracenePhenanthreneFluorene

Volatile PAHsDimethyl naphthaleneAcenaphtheneAcenaphthyleneDimethyl naphthaleneBiphenyl1-methyl naphthalene2-methyl naphthaleneNaphthalene

FILTER

��

��

��

��

��

��

��

PUF

XAD

Expected PAH phase distribution in ambient and exhaust samples

Polycyclic Aromatic Hydrocarbons


PM-PAHs - CBD

0

3

6

9

12

Diesel

(OC)

Diesel

(DPF)

CNG.00a

CNG.00b

CNG.00 (O

C)CNG.01

(OC)


Emis

sion

s (u

g/m

i) 45


SV-PAHs - CBD

0

50

100

150

200

Diesel

(OC)

Diesel

(DPF)

CNG.00a

CNG.00b

CNG.00 (O

C)CNG.01

(OC)


Emis

sion

s (u

g/m

i) 265


V-PAHs - CBD

0

50

100

150

200

Diesel

(OC)

Diesel

(DPF)

CNG.00a

CNG.00b

CNG.00 (O

C)CNG.01

(OC)


Emis

sion

s (u

g/m

i)

405 196

Mutagenic Potency

Specific Activity (Potency) - CBD

0

10

20

30

Diesel

(OC)

Diesel

(DPF)

CNG.00a

CNG.00b

CNG.00 (O

C)CNG.01

(OC)


Spec

ific

Mut

agen

iAct

ivity

(R

ev/u

g)

Mutagen Emissions - CBD

Mutagen Emissions

0

2

4

6

8

Diesel

(OC)

Diesel

(DPF)

CNG.00a

CNG.00b

CNG.00 (O

C)CNG.01

(OC)


Emis

sion

s (r

ev/m

i x 1

0 5) PM

SV

HYDROCARBON ANALYSIS

• Tedlar Bag Sampling

• Onsite GC to limit hold time

• SOP # MLD 102/103GC/FID Analysis w/cryo-trappingSpeciation of C2-C12+

• Report:Benzene, Toluene, EthylBenzene, Xylenes (BTEX)and

1,3 Butadiene

• GC/MS Confirmation of BTEX

10 20 30 40 50 60 70

Minute s

-1

0

5

10

15

20

25

30

mVolts

Propane/Propene< 5% of NMHC

Mid Range Chromatogram (T03013; 04/20/01)Diesel fueled bus no trap, CBD cycle

C2 Hydrocarbons< 15% of NMHC

n-Alkanes (C9+)

Toluene

Benzene

5 10 15 20 25 30 35 40

Minute s

0.0

0.5

1.0

1.5

2.0

Volts

Propane/Propene~ 20% of NMHC

Mid Range Chromatogram (T03130; 06/07/01) CNG fueled bus, CBD cycle

C2 Hydrocarbons~ 70% of NMHC

Isopentanen-Butane

TolueneBenzene

25.00 25.25 25.50 25.75 26.00 26.25

Minute s

-2

0

10

20

30

40

50

mVolts

Partial Light End Chromatogram - (04/20/01)CNG fueled bus; CBD cycle

Isopentane

Pentane

1,3 Butadiene

Total BTEX and Benzene Emission (CBD Cycle)(Error bars represent 1 std dev of replicate measurements)

(Tunnel blank value = average of mass emissions/miles per cycle)

0

2

4

6

Tunnel Blank Diesel (OC) Diesel (DPF) CNG.00 CNG.00 (OC) CNG.01 (OC)

Em

iss

ion

Ra

te (

mg

/

Total BTEX

Benzene

1,3 Butadiene Average Emission (CBD Cycle)(Error bars represent 1 std dev of replicate measurements)


0

1

2

3

4

5


Em

issi

on R

ate

(mg/

mi 1,3 Butadiene

1,3 Butadiene was not detected for any vehicle

configuration ortunnel blank except

CNG.00 Without OxiCat

Carbonyl Analysis

• Heated line Sampling

• DNPH Coated Silica Cartridges

• SOP # MLD 104Extraction with AcetonitrileHPLC analysis w/ UV Detection13 Target Compounds

Average Carbonyl Emissions (CBD Driving Cycle)(Error bars for carbonyl sum derived from 1 std dev of replicate runs)


0

200

400

600

800

1000

1200


Em

iss

ion

(m

g/m

Hexanal

m-Tolualdehyde

Valeraldehyde

Crotonaldehdye

Benzaldehyde

Methacrolein

Methyl Ethyl Ketone

Butanal

Propanal

Acetone

Acrolein

Acetaldehyde

Formaldehyde

Both OxiCat and DPF usage show large

reduction in formaldehyde

Summary• DPF reduces PM,, CO, HC, NMHC, EC, OC,

elements• DPF also reduces carbonyls, VOCs, PM-bound

and semivolatile PAHs, and PM-bound andsemivolatile mutagen emissions

• CNG catalyst reduces PM, OC, CO, HC, NMHC, CH4

• CNG catalyst also reduces carbonyls, VOCs, semivolatile PAHs, and PM-bound and semivolatile mutagen emissions

Summary

• NOX from CNG engines approximately 50% lower than NOX from diesel engine

• DPF-equipped bus has NOX emissions that contain 50% NO2

• Although not shown, test cycle differences are seen

• After-treatment durability and deterioration and vehicle maintenance were not evaluated

Acknowledgements

We wish to thank Mindy Salazar, Julia Sandoval, T.S. Yeung, Shiou-mei Huang, Richard Ling, Lyman Dinkins, Norma Castillo, Jack Horrocks, Keshav Sahay, George Gatt, John Karim, Jim Shears, Namita Verma, Wayne McMahon, Mark Fuentes, Bart Croes, Hector Maldonado, Richard Bode, Richard Corey, Linda Smith from the ARB.

Acknowledgements

We also are grateful to: Keith Stiglitz, Fred Gonzalez, and Harvey Porter of CAVTC; Geraldine Navarro, Kelsie Takasaki, Bernice Cheng, Mary Manaloto from UC Davis; Brit Holmen, UConn; Steve Barbosa of the SCAQMD. We also thank: LACMTA, So. Cal Gas Co., BP/ARCO, Detroit Diesel, San Bernardino Rapid Transit. We thank the Air Resources Board and SCAQMD for their support.

Date post:	11-Jun-2018
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