The best green truck option for the refuse segment at this stage is a dual-fuel truck that runs on liquefied natural gas (LNG) and diesel — enabling the truck to function solely on diesel fuel should its LNG tanks run dry for any reason. While there are significant extra costs to equip a fleet of refuse trucks to operate on LNG, there are several benefits including lower emissions and less noise, along with significantly lower fuel costs per gallon over time.
San Diego's refuse collection division began buying refuse trucks powered by LNG over a decade ago and reports spending $20,000 to $30,000 more per vehicle over a diesel-only model, says Chuck Woolever, deputy director for the city's refuse collection division. San Diego, however, received federal and state grants to cover the difference for the vehicles, as well as similar aid to build an LNG refueling station that cost the city over $500,000 to build.
“We took a hard look at our application needs. We had to make sure that whatever alternative fuel we chose would still accomplish the duty cycle required of our vehicles,” says Woolever. “We chose the dual-fuel LNG/diesel trucks that use diesel fuel to ‘pilot ignite’ the LNG. Even though these trucks run almost completely on LNG, the dual-fuel configuration gave us an option to operate completely on diesel if we ran out of LNG on the road.”
Each of San Diego's LNG trucks is equipped with 199 gal. of LNG fuel storage, as that roughly equals the range of its 60-gal. diesel-only trucks.
According to a study by New York City-based environmental consulting firm Inform Inc., the higher cost per LNG-powered refuse truck, which its research pegged at $210,000 to $225,000 vs. $170,000 for a diesel-only model, must be balanced by lower fuel costs and other green benefits. The company says LNG-powered refuse trucks emit 67 to 90% less particulate matter, 32 to 73% fewer oxides of nitrogen (NOx), and reduce non-methane hydrocarbon (NMHC) emissions anywhere from 69 to 83%. Noise reduction is another positive, Inform says. The group notes that LNG produces 50% fewer decibels behind a refuse truck, 90% fewer within the truck cab, and 98% fewer alongside the truck's exterior compared to a diesel-only powered vehicle.
Using LNG also allows for a faster refueling rate, as a truck can fill up on the liquefied form of natural gas in nine to ten minutes compared to the eight to nine hours needed for heavy trucks powered by compressed natural gas.
Perhaps the biggest payoff in the near future for refuse companies is the potential to capture the methane gas released as a byproduct of trash decomposition in landfills and convert it into LNG. “If we can manage to make consistent quality truck fuel from landfill gas, it's a huge opportunity for refuse fleets,” says David McKenna, product marketing manager for engines, transmissions and axles at Mack Trucks, which has participated in landfill-gas reclamation projects.
“Basically, your landfill becomes your own little Saudi Arabia. And when diesel fuel is costing between $4 and $5 a gallon, it suddenly becomes much more economic on a long-term basis to be able to make your own fuel. It's a win-win for everyone.”