With 6,000 compressed natural gas (CNG) trucks in its fleet, Waste Management has more of the heavy-duty alt fuel trucks than any other company in North America.
When possible, Waste Management fuels its CNG trucks with renewable natural gas, which is produced from biogas generated at landfills or anaerobic digesters. About one-third of its fleet uses biogas and 100 percent of its California fleet runs on renewable natural gas.
Waste Management, which has been using natural gas in its fleet since the early 1990s, took the time to answer questions regarding their experience with CNG technology.
HWT: Have CNG trucks required less maintenance than their diesel counterparts? If so, please describe.
WM: Yes, because of the cleaner gaseous fuel there is no need for complicated high pressure fuel injection and emission after treatment systems.
HWT: Has power (horsepower and torque) ever been a concern with CNG trucks?
WM: With any new technology there are compromises, we have mitigated most of those issues with transmission and gearing adjustments.
HWT: Did you lose some payload capacity in switching to CNG?
WM: Yes, but we are working with state governments on the federally passed natural gas weight exemption programs.
HWT: What kind of CNG engine, or engines, do you use?
WM: Cummins 9 and 12-liter engines.
HWT: How have the CNG tanks and lines held up? How often do you have to check them?
WM: They are very reliable and we have a robust inspection program to ensure their integrity.
HWT: Please describe any training that drivers undergo prior to getting behind the wheel of a CNG truck.
WM: In addition to our daily safety meetings, we have annual driver safety awareness training.
HWT: Gasoline and diesel are rated by their octane and cetane levels, respectively. Is there a particular brand and/or grade of CNG that you like to use?
WM: No, the closest thing to that type of measurement system is the Cummins gas quality calculator which we use as a minimum standard.
HWT: When refueling, do you prefer a slow-fill or fast-fill CNG pump?
WM: Unequivocally slow fill.
HWT: Any performance differences between CNG and RNG?
WM: None, both are tested.
HWT: Do you have to undergo additional inspections when using natural gas?
WM: We have a robust inspection and maintenance program for all types of fuel systems.