See journal paper at http://dx.doi.org/10.1016/j.atmosenv.2014.04.036 According to a 2006 report, the waste collection industry in the U.S. operates over 136,000 refuse trucks, almost all diesels, that average 25,000 miles annually and with average fuel economy of less than 3 miles per gallon. There is an increasing adoption of Compressed Natural Gas (CNG) fuelled trucks in the waste collection industry due to the significantly lower cost of CNG per diesel gallon equivalent (dge). This presentation includes results of activity and fuel use from in-use real-world field measurements of eighteen diesel fuelled refuse trucks, with six each of side-load, front-load, and roll-off configurations and six CNG fuelled refuse trucks, with three each of side-load and front-load configurations. The study design included trucks from various manufacturers such as Mack, Autocar, and Freightliner and model years 2003 to 2012. Each truck was instrumented for one day of operation with a portable activity measurement system (PAMS) to log Engine Control Unit (ECU) data and Global Positioning System (GPS) receivers. Trucks were also instrumented with portable emissions measurement system (PEMS), however, emissions results are not included here. The total quality assured data covers over 2,000 miles and 190 hours of in-use real-world driving. During the measurement period the trucks picked about 7,500 cans with a total of over 500 tons of trash. Measured 1 Hz activity data includes, but is not limited to, vehicle speed, engine speed, intake manifold pressure, intake air temperature, engine load, and elevation (leading to road grade). Duty cycles and fuel use rates are quantified in terms of operating mode bins defined by the U.S. Environmental Protection Agency for the MOVES emission factor model. Overall results are included here; detailed results by truck configuration and fuel type will be covered in the presentation. On average, 50 percent of time was spent at idle, 5 percent braking or decelerating, 28 percent at low speed (up to 25 mph), 12 percent at moderate speed (25 to 50 mph), and 5 percent at high speed (50 mph or higher). Diesel trucks spend more time in high speed mode compared to CNG. Estimated cycle average diesel fuel economy ranges were 2.0 to 3.4 mpg, 2.3 to 3.2 mpg, 3.9 to 6.0 mpg, and for side-loaders, front-loaders, and roll-offs, respectively. In comparison, CNG fuel economy ranges were 1.2 to 1.7 mpdge and 2.0 to 2.5 mpdge for side-loaders and front-loaders, respectively.

1. 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
1
2

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. 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. 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. 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?

6. 6
Roll-off Refuse Truck Activity
1
2
4
3

7. 7
Front-loader Refuse Trucks Activity
1
2
4
3

8. 8
Side-loader Refuse Trucks Activity
1
2
4
3

9. 9
Measured Diesel Roll-off Trucks
RO-1RO-2RO-3RO-4RO-5RO-6Year200520062007200720122012MakeMackMackMackMackMackMackModelCV713CV713CV713CV713GU 713GU 713Year200520052006200620122012MakeMackMackMackMackMackMackModelAMI-370AMI-335AMI-335AMI-335MP7-405MMP7-405MDispl. (L)11.911.911.911.911.011.0Hp405365365365405405EGREGREGREGREGR,DPF, SCREGR, DPF, SCR362,037445,734320,805303,63581,58881,903DPF - Diesel Particulate Filter; EGR - Exhaust Gas Recirculation; SCR – Selective Catalytic ReductionTruckChassisEngineEmissions ControlsMileage

10. 10
Measured Diesel Front-loader Trucks
FL-1FL-2FL-3FL-4FL-5FL-6Year200420052008200820102010MakeMackMackAutocarMackAutocarAutocarModelMR6885MR6885WX64MRU 613XpeditorXpeditorYear200420042006200820072007MakeMackMackCumminsMackCumminsCumminsModelAI-350AI-350ISM-320VMP7 325MISL-365ISL-365Displ. (L)12.012.010.811.08.98.9Hp350350320325365365EGREGREGREGR, DPFEGR, DPFEGR, DPF284,003267,971184,934117,69150,03341,017DPF - Diesel Particulate Filter; EGR - Exhaust Gas RecirculationTruckChassisEngineEmissions ControlsMileage

11. 11
Measured Diesel Side-loader Trucks
SL-1SL-2SL-3SL-4SL-5SL-6Year200320032008200920102012MakeMackMackFreightlinerMackFreightlinerFreightlinerModelLE 613LE 613M2 106LEU 613M2M2Year200320032008200820102012MakeMackMackDetroit DieselMackCumminsCumminsModelAI-300AAI-300AMBE 900MP7-325MISC-300ISC-300Displ. (L)12.012.07.211.08.38.3Hp325325250325300300--EGR, DPFEGR, DPFEGR, DPFEGR, DPF, SCR236,913292,135108,81488,78175,48040,097DPF - Diesel Particulate Filter; EGR - Exhaust Gas Recirculation; SCR – Selective Catalytic ReductionTruckChassisEngineEmissions ControlsMileage

12. 12
Measured CNG Trucks
FLC-1FLC-2FLC-3SLC-1SLC-2SLC-3YearMakeModelYearMakeModelDispl. (L) Hp27,67035,55130,53423,19725,17725,317EGR - Exhaust Gas Recirculation; TWC – Three Way Catalyst320320EGR, TWCEGR, TWCTruckFront-loaderSide-loader Cummins Cummins ISLG-320 ISLG-320 8.98.9Emissions ControlsMileage20132012 Mack Autocar ACX64 MRU633 20122012ChassisEngine

13. 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

14. 14
Instrumentation
PEMS: GlobalMRV Axion
ECU Readout
Exhaust Probes
GPS units: Garmin 76CSx

15. 15
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)

16. 16
Time Alignment Example: CO2 vs. Fuel Use

17. 17
Correlation Coeff Example: CO2 vs. Fuel Use

18. 18
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
23() 100tttttttscalerAvBvCvmvagSTPf  

19. 19
MOVES Operating Mode Definition
06121824303601111213141516212223242527282930333537383940 Scaled Tractive Power, skW MOVES Operating Mode1 mph ≤ Speed < 25 mph25 mph ≤ Speed < 50 mph50 mph ≤ Speed IdlingDeceleratingCoasting, STP < 0Coasting, STP < 0 ....

20. 20
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

21. 21
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

22. 22
Route of Roll-off 3
170 miles 7 cans 52 tons

23. 23
Route of Front-loader 2
157 miles
110 cans
28.3 tons

24. 24
Route of Side-loader 4
88 miles
1100 cans
18.3 tons

25. 25
Speed Trace for One Trip of Roll-off 3
U = Urban (arterial) driving, no trash collection; H = Highway driving; L = Landfill; TC = Trash Collection
020406080010002000300040005000 Speed (mph) Time (seconds) UHUTCHUUL1 can

26. 26
Speed Trace for One Trip of Front-loader 2
U = Urban (arterial) driving, no trash collection; H = Highway driving; L = Landfill; TC = Trash Collection
020406080020004000600080001000012000 Speed (mph) Time (seconds) UHUTCHUUL25 cans

27. 27
Speed Trace for One Trip of Side-loader 4
U = Urban (arterial) driving, no trash collection; H = Highway driving; L = Landfill; TC = Trash Collection
0204060800400080001200016000 Speed (mph) Time (seconds) UHUTCUL450 cans

28. 28
Comparison of Duty Cycles: Diesel vs CNG
02040608001111213141516212223242527282930333537383940 % Time Spent in OpMode MOVES Operating ModeNCSU Diesel Front-L RTNCSU CNG Front-L RTNCSU Diesel Side-L RTNCSU CNG Side-L RT1 mph ≤ Speed < 25 mph25 mph ≤ Speed < 50 mph50 mph ≤ Speed IdlingDecelerating Within a speed range, higher modes represent greater engine power demand

29. 29
Comparison of Duty Cycles: NCSU vs Literature
02040608001111213141516212223242527282930333537383940 % Time Spent in OpMode MOVES Operating ModeNCSU Roll-off RTNCSU Front-loader RTNCSU Side-loader RTCentral Business DistrictNew York Garbage Truck1 mph ≤ Speed < 25 mph25 mph ≤ Speed < 50 mph50 mph ≤ Speed IdlingDecelerating Within a speed range, higher modes represent greater engine power demand

30. 30
Example: Modal Fuel Use Rates for RO-3
051015202501111213141516212223242527282930333537383940 Fuel Use (g/s) MOVES Operating Mode1 mph ≤ Speed < 25 mph25 mph ≤ Speed < 50 mph50 mph ≤ Speed IdlingDecelerating Within a speed range, higher modes represent greater engine power demand

31. 31
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
Truck
Fuel
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
Truck
Fuel
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
Truck
Fuel
Side-loader
Average: 2.9
Max/Min: 2.1

32. 32
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
Truck
Fuel
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
Truck
Fuel
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
Truck
Fuel
Side-loader
Max/Min: 2.0

33. 33
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
Truck
Fuel
g/s mi/DGE
SLC-1 2.6 1.1
SLC-2 3.7 2.0
SLC-3 2.4 1.5
Truck
Fuel
Diesel Avg: 2.6 Diesel Avg: 2.9
CNG fuel use rates are based on preliminary data analysis

34. 34
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
Fuel
Truck
g/s mi/DGE
SLC-1 2.8 1.6
SLC-2 3.3 1.4
SLC-3 2.6 1.8
Fuel
Truck
CNG fuel use rates are based on preliminary data analysis

35. 35
Exploratory Analysis: Diesel Fuel Use, SL-1

36. 36
Exploratory Analysis: Diesel NOx Rates, SL-1

37. 37
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.

38. 38
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.

39. 39
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.

40. 40
Gurdas S. Sandhu
gssandhu@ncsu.edu
Questions Invited

41. 41
ADDITIONAL MATERIAL

42. 42
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.