The City of Scottsdale, Ariz., has more than tripled its use of compressed natural gas (CNG) and increased its use of E-85 by almost seven fold over the past two fiscal years.

These increases were achieved through customer awareness efforts, increased availability of alternative fuels, and vehicle replacements with alternative fuels when possible, said Mel Galbraith, PCFM, fleet director with the city.

Between fiscal-years 2012 and 2014, the city's CNG use has increased from 18,000 to 93,000 diesel gallon equivalents and its E-85 use has increased from less than 4,000 gallons to 27,600 gallons, he said.

The city began its CNG investment in 1995 with bi-fuel pick-up trucks. With its move to alt-fuels, the fleet focused on heavy trucks for CNG conversion because there was a potential return on investment on them.

In 2012, the fleet began with a pilot of four CNG solid waste vehicles. When complaints came back from drivers saying the trucks had no acceleration, which is important for the residential side loaders, fleet staff worked with the manufacturer to make modifications.

"They did some fine-turning on the engine, the computer system, and they also changed the final drive ratio to give them a quicker launch," Galbraith said. Drivers have been happy with the modified trucks.

"They get the routes done on time, and [the trucks] are considerably quieter," Galbraith said. "The fuel is quite a bit cheaper." How much cheaper? The city pays $1.49 per diesel gallon equivalent for CNG, which includes fueling station maintenance and amortization costs, while diesel costs $3.38 per gallon.

With these fuel prices, a return on investment for the $40,000 higher up-front cost of a CNG residential side loader doesn't take very long. Fleet staff say that with these trucks, the city gets ROI in 3.2 years. For the other refuse vehicles, staff expects payback would be even quicker.

In addition to CNG, the fleet has expanded its E-85 use. With 177 flex-fuel vehicles, and with E-85 selling at about 30 cents less than gasoline, fleet staff is hoping more drivers fuel with E-85. Fueling with the biofuel is on a voluntary basis. However, a second E-85 dispenser installed just last month, chosen based on flex-fuel vehicle fuel pumping patterns, as well as periodic reports to user department heads encouraging the fuel use, has already increased E-85 use.

The city currently has 10 CNG solid waste trucks and 40 that run on diesel. With 13 CNG trucks currently on order replacing diesel trucks, the percentage of CNG trucks in solid waste will jump to 46% by the end of the fiscal year, further increasing alternative-fuel use in the city fleet.

By Thi Dao