Real-World Activity and Fuel Use

of Diesel and CNG Refuse Trucks

Gurdas Sandhu1

H. Christopher Frey1

Shannon Bartelt-Hunt2

Elizabeth Jones2

@ 2014 PEMS International Conference & Workshop » April 3-4 » Riverside, California

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2

2

Waste Collection in U.S.

~ 250 million tons of municipal solid waste generated each year

~ 140,000 refuse trucks for collection and transportation

Trucks average 25,000 miles per year

Typical fuel economy of 2 to 3 mpg of diesel

3

Motivation

Very few studies that report real-world diesel or natural gas refuse truck duty cycles and fuel use rates.

No study that compares real-world duty cycles and fuel use rates between refuse truck configurations.

4

Study Overview

“Include refuse truck configurations, model years & emissions control devices, and fuels typical to the U.S. waste collection industry.”

24 Trucks (18 diesel, 6 CNG)

Roll-off, Front-loader, and Side-loader configurations

Model Years: 2003 to 2012

Fuels: Ultra Low Sulfur Diesel (ULSD) and Compressed Natural Gas (CNG)

5

Research Questions

1. What are the real-world duty cycles of roll-off, front-loader, and side-loader refuse trucks?

2. What are the real-world fuel use rates of diesel roll-off, front-loader, and side-loader refuse trucks?

3. What are the real-world fuel use rates of CNG front-loader and side-loader refuse trucks?

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Roll-off Refuse Truck Activity

1 2

4 3

7

Front-loader Refuse Trucks Activity

1 2

4 3

8

Side-loader Refuse Trucks Activity

1 2

4 3

9

Measured Diesel Roll-off Trucks

RO-1 RO-2 RO-3 RO-4 RO-5 RO-6

Year 2005 2006 2007 2007 2012 2012

Make Mack Mack Mack Mack Mack Mack

Model CV713 CV713 CV713 CV713 GU 713 GU 713

Year 2005 2005 2006 2006 2012 2012

Make Mack Mack Mack Mack Mack Mack

Model AMI-370 AMI-335 AMI-335 AMI-335 MP7-405M MP7-405M

Displ. (L) 11.9 11.9 11.9 11.9 11.0 11.0

Hp 405 365 365 365 405 405

EGR EGR EGR EGR EGR,DPF, SCR EGR, DPF, SCR

362,037 445,734 320,805 303,635 81,588 81,903

DPF - Diesel Particulate Filter; EGR - Exhaust Gas Recirculation; SCR – Selective Catalytic Reduction

Truck

Chassis

Engine

Emissions Controls

Mileage

10

Measured Diesel Front-loader Trucks

FL-1 FL-2 FL-3 FL-4 FL-5 FL-6

Year 2004 2005 2008 2008 2010 2010

Make Mack Mack Autocar Mack Autocar Autocar

Model MR6885 MR6885 WX64 MRU 613 Xpeditor Xpeditor

Year 2004 2004 2006 2008 2007 2007

Make Mack Mack Cummins Mack Cummins Cummins

Model AI-350 AI-350 ISM-320V MP7 325M ISL-365 ISL-365

Displ. (L) 12.0 12.0 10.8 11.0 8.9 8.9

Hp 350 350 320 325 365 365

EGR EGR EGR EGR, DPF EGR, DPF EGR, DPF

284,003 267,971 184,934 117,691 50,033 41,017

DPF - Diesel Particulate Filter; EGR - Exhaust Gas Recirculation

Truck

Chassis

Engine

Emissions Controls

Mileage

11

Measured Diesel Side-loader Trucks

SL-1 SL-2 SL-3 SL-4 SL-5 SL-6

Year 2003 2003 2008 2009 2010 2012

Make Mack Mack Freightliner Mack Freightliner Freightliner

Model LE 613 LE 613 M2 106 LEU 613 M2 M2

Year 2003 2003 2008 2008 2010 2012

Make Mack Mack Detroit Diesel Mack Cummins Cummins

Model AI-300A AI-300A MBE 900 MP7-325M ISC-300 ISC-300

Displ. (L) 12.0 12.0 7.2 11.0 8.3 8.3

Hp 325 325 250 325 300 300

- - EGR, DPF EGR, DPF EGR, DPF EGR, DPF, SCR

236,913 292,135 108,814 88,781 75,480 40,097

DPF - Diesel Particulate Filter; EGR - Exhaust Gas Recirculation; SCR – Selective Catalytic Reduction

Truck

Chassis

Engine

Emissions Controls

Mileage

12

Measured CNG Trucks

FLC-1 FLC-2 FLC-3 SLC-1 SLC-2 SLC-3

Year

Make

Model

Year

Make

Model

Displ. (L)

Hp

27,670 35,551 30,534 23,197 25,177 25,317

EGR - Exhaust Gas Recirculation; TWC – Three Way Catalyst

320 320

EGR, TWC EGR, TWC

Truck Front-loader Side-loader

Cummins Cummins

ISLG-320 ISLG-320

8.9 8.9

Emissions Controls

Mileage

2013 2012

Mack Autocar

ACX64 MRU633

2012 2012

Chassis

Engine

13

CNG Fuel System

Full fuel tank: 3600 psi At engine inlet: 70-150 psi Inside engine: 40-70 psi

1 diesel gallon equivalent (DGE) of CNG costs ~ $1.80

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Instrumentation

PEMS: GlobalMRV Axion

ECU Readout

Exhaust Probes

GPS units: Garmin 76CSx

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Data Collected

Exhaust pollutants: Carbon Dioxide (CO2), Carbon Monoxide (CO), Hydrocarbons (HC), Nitric Oxide (NO), and Particulate Matter (PM).

Engine Data: Vehicle Speed (kph), Engine Speed (rpm), Intake Air Temperature (oC), Intake Manifold Pressure (kPa), Fuel Use Rate (L/hr), Engine Load (%), Torque (%), and Exhaust Temperature (oC).

Location Data: Latitude, Longitude, Elevation (m)

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Time Alignment Example: CO2 vs. Fuel Use

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Correlation Coeff Example: CO2 vs. Fuel Use

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MOVES Scaled Tractive Power

STPt = scaled tractive power at time t, skW A = rolling resistance coefficient [kW-s/m] {1.41705} B = rotational resistance coefficient [kW-s2/m2] {0} C = aerodynamic drag coefficient [kW-s3/m3] {0.003572} at = vehicle acceleration at time t [m/s2] g = acceleration due to gravity [9.81 m/s2] m = vehicle mass [metric ton] {20.6845} rt = road grade at time t [%] vt = vehicle speed at time t [m/s] fscale = scaling factor, 17.1 unitless

2 3 ( )100

tt t t t t

t

scale

rAv Bv Cv mv a g

STPf

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MOVES Operating Mode Definition

0

6

12

18

24

30

36

0 1 11 12 13 14 15 16 21 22 23 24 25 27 28 29 30 33 35 37 38 39 40

Scal

ed

Tra

ctiv

e P

ow

er,

skW

MOVES Operating Mode

1 mph ≤ Speed < 25 mph 25 mph ≤ Speed < 50 mph 50 mph ≤ Speed

Idlin

g

Dec

eler

atin

g

Co

asti

ng,

STP

< 0

Co

asti

ng,

STP

< 0

....

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Activity Overview for Diesel Trucks

Roll-off Front

loader Side

loader Total

1Hz QA Data (hours) 50 48 46 144

Miles Driven 870 780 555 2,205

Fuel Used (gal) 199 285 210 694

Trash Cans Picked 39 660 4,200 4,900

Trash Collected (tons) 165 150 50 365

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Activity Overview for CNG Trucks

Front loader

Side loader

Total

1Hz QA Data (hours) 30 20 50

Miles Driven 324 169 493

Fuel Used (DGE) 145 116 261

Trash Cans Picked 416 2110 2526

Trash Collected (tons) 105 28 133

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Route of Roll-off 3

170 miles 7 cans

52 tons

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Route of Front-loader 2

157 miles 110 cans 28.3 tons

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Route of Side-loader 4

88 miles 1100 cans 18.3 tons

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Speed Trace for One Trip of Roll-off 3

U = Urban (arterial) driving, no trash collection; H = Highway driving; L = Landfill; TC = Trash Collection

0

20

40

60

80

0 1000 2000 3000 4000 5000

Sp

eed

(m

ph

)

Time (seconds)

U H U TC H UU L

1 can

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Speed Trace for One Trip of Front-loader 2

U = Urban (arterial) driving, no trash collection; H = Highway driving; L = Landfill; TC = Trash Collection

0

20

40

60

80

0 2000 4000 6000 8000 10000 12000

Sp

eed

(m

ph

)

Time (seconds)

U H U TC H UU L

25 cans

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Speed Trace for One Trip of Side-loader 4

U = Urban (arterial) driving, no trash collection; H = Highway driving; L = Landfill; TC = Trash Collection

0

20

40

60

80

0 4000 8000 12000 16000

Sp

eed

(m

ph

)

Time (seconds)

U H U TC U L

450 cans

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Comparison of Duty Cycles: Diesel vs CNG

0

20

40

60

80

0 1 11 12 13 14 15 16 21 22 23 24 25 27 28 29 30 33 35 37 38 39 40

% T

ime

Sp

en

t in

Op

Mo

de

MOVES Operating Mode

NCSU Diesel Front-L RT

NCSU CNG Front-L RT

NCSU Diesel Side-L RT

NCSU CNG Side-L RT

1 mph ≤ Speed < 25 mph 25 mph ≤ Speed < 50 mph 50 mph ≤ Speed

Idlin

gD

ecel

erat

ing

Within a speed range, higher modes represent greater engine power demand

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Comparison of Duty Cycles: NCSU vs Literature

0

20

40

60

80

0 1 11 12 13 14 15 16 21 22 23 24 25 27 28 29 30 33 35 37 38 39 40

% T

ime

Sp

en

t in

Op

Mo

de

MOVES Operating Mode

NCSU Roll-off RT

NCSU Front-loader RT

NCSU Side-loader RT

Central Business District

New York Garbage Truck

1 mph ≤ Speed < 25 mph 25 mph ≤ Speed < 50 mph 50 mph ≤ Speed

Idlin

gD

ecel

erat

ing

Within a speed range, higher modes represent greater engine power demand

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Example: Modal Fuel Use Rates for RO-3

0

5

10

15

20

25

0 1 11 12 13 14 15 16 21 22 23 24 25 27 28 29 30 33 35 37 38 39 40

Fue

l Use

(g

/s)

MOVES Operating Mode

1 mph ≤ Speed < 25 mph 25 mph ≤ Speed < 50 mph 50 mph ≤ Speed

Idlin

g

Dec

eler

atin

g

Within a speed range, higher modes represent greater engine power demand

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Diesel Fuel Use Rates for Observed Cycles

g/s mi/gal

RO-1 3.0 4.5

RO-2 2.6 4.0

RO-3 3.6 4.0

RO-4 3.1 3.9

RO-5 2.4 6.0

RO-6 2.5 4.9

TruckFuel

Roll-off

Average: 4.6 Max/Min: 1.5

g/s mi/gal

FL-1 5.1 3.2

FL-2 3.8 2.6

FL-3 4.9 2.1

FL-4 3.5 2.4

FL-5 4.5 2.6

FL-6 3.8 2.3

TruckFuel

Front-loader

Average: 2.6 Max/Min: 1.5

g/s mi/gal

SL-1 3.8 2.8

SL-2 3.9 2.1

SL-3 2.5 3.3

SL-4 4.0 2.0

SL-5 2.1 3.1

SL-6 2.0 4.2

TruckFuel

Side-loader

Average: 2.9 Max/Min: 2.1

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Diesel Fuel Use Rates for Average Cycle

g/s mi/gal

FL-1 4.3 2.5

FL-2 4.1 2.6

FL-3 4.5 2.4

FL-4 4.0 2.8

FL-5 4.4 2.5

FL-6 4.3 2.5

TruckFuel

Front-loader

Max/Min: 1.2

g/s mi/gal

RO-1 2.9 4.4

RO-2 3.1 4.2

RO-3 3.3 3.9

RO-4 3.0 4.4

RO-5 2.4 5.5

RO-6 2.6 4.9

TruckFuel

Roll-off

Max/Min: 1.4

g/s mi/gal

SL-1 3.5 2.3

SL-2 4.2 2.0

SL-3 2.3 3.6

SL-4 3.7 2.2

SL-5 2.6 3.2

SL-6 2.0 4.0

TruckFuel

Side-loader

Max/Min: 2.0

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CNG Fuel Use Rates for Observed Cycles

Front-loader

Average: 2.3 Max/Min: 1.2

Side-loader

Average: 1.5 Max/Min: 1.8

g/s mi/DGE

FLC-1 3.4 2.3

FLC-2 3.7 2.6

FLC-3 3.5 2.1

TruckFuel

g/s mi/DGE

SLC-1 2.6 1.1

SLC-2 3.7 2.0

SLC-3 2.4 1.5

TruckFuel

Diesel Avg: 2.6 Diesel Avg: 2.9

CNG fuel use rates are based on preliminary data analysis

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CNG Fuel Use Rates for Average Cycle

Front-loader

Max/Min: 1.0

Side-loader

Max/Min: 1.3

g/s mi/DGE

FLC-1 3.5 2.3

FLC-2 3.5 2.3

FLC-3 3.5 2.3

FuelTruck

g/s mi/DGE

SLC-1 2.8 1.6

SLC-2 3.3 1.4

SLC-3 2.6 1.8

FuelTruck

CNG fuel use rates are based on preliminary data analysis

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Exploratory Analysis: Diesel Fuel Use, SL-1

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Exploratory Analysis: Diesel NOx Rates, SL-1

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Conclusions for Duty Cycles

Refuse truck duty cycles vary with configuration and are different from cycles used in previous studies.

EPA’s MOVES model should include at least one refuse truck duty cycle.

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Conclusions for Fuel Use Rates

A higher value for fuel economy must be considered for roll-off configurations.

On average, compared to diesel, CNG trucks have lower fuel economy.

Overall fuel economy is not adversely affected by emissions controls; the adverse effect (if any) of only the emissions control device is offset by other efficiency measures.

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Acknowledgements

This work is sponsored by the Environmental Research and Education Foundation (EREF).

Waste Industries (WI) provided refuse trucks for measurement at their Garner and Durham facilities in North Carolina, with extensive support from management staff, technical staff, and drivers.

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Gurdas S. Sandhu

gssandhu@ncsu.edu

Questions Invited

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ADDITIONAL MATERIAL

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MOVES STP References

Development of Emission Rates for Heavy-Duty Vehicles in the Motor Vehicle Emissions Simulator MOVES2010. US EPA; 420-B-12-049; August 2012.

Development of Emission Rates for Light-Duty Vehicles in the Motor Vehicle Emissions Simulator (MOVES2010). US EPA; 420-R-11-011; August 2011.

MOVES2010 Highway Vehicle: Population and Activity Data. US EPA; 420-R-10-026; November 2010.