Alternatively fueled or powered vehicles currently make up 43 percent of the city’s total fleet. The city has switched all diesel-powered vehicles to B20 biodiesel and is purchasing hybrid models as older, light-duty vehicles in the fleet are replaced. Credit: Denver Public Works.

Denver’s Green Fleet

The greening of Denver’s fleet began on Earth Day in 1993 when the city created the first Green Fleet program in the nation.

Enacted through an executive order by former mayor Wellington E. Webb, and later revised in 2000, the program calls for a reduction in carbon emissions and fuel expenditures by having the city adopt a number of environmentally-friendly strategies, including purchasing smaller
vehicles, encouraging the use of alternative modes of transportation, minimizing total vehicle miles, and investing in alternatively fueled vehicles.

Hybrid Technology

In 2001, the program reached a significant milestone when the city purchased 39 hybrid electric Toyota Prius sedans. These passenger cars quickly became favorites of city staff, and the purchase elevated awareness of the city’s commitment to hybrid technology as a viable solution to reduce air pollution and fuel costs. The fleet expanded steadily over the next several years and different makes and models were added, including three new Ford Escape SUVs in 2005. The city’s fleet now includes a total of 138 hybrid vehicles.

Hybrids have both an electric motor and a gasoline engine, which work differently depending on the type of vehicle. Both the Prius and Escape models use an electric motor at low speeds and then switch to a gasoline engine at higher speeds. The electric motor and the gas engine work in tandem when driving conditions demand more power, such as while climbing a hill, during hard acceleration, or when passing other vehicles. In normal city use, these cars average more than 40 miles per gallon.

Alternative Fuels Program

Denver was also an early adopter of alternative fuels. In 1990, Denver City Council approved an alternative fuels ordinance to promote cleaner air. The following year, the city ran one of the pioneering studies to test a fuel called Hythane™, a mixture of 15 percent hydrogen and 85 percent compressed natural gas.

The trial helped researchers gain a better understanding of the potential of hydrogen technology, and led to the city’s exploration and use of other alternative fuels such as CNG and propane. Hydrogen/natural gas blends are still being tested in demonstration projects by several organizations worldwide. They have been found to significantly reduce nitrogen oxides emissions, and are helping pave the way toward hydrogen-based transportation solutions of the future.

In 2004, the city launched a pilot program to test approximately 50,000 gallons of B20 biodiesel in 60 of the city’s standard diesel engine vehicles. Biodiesel is an alternative fuel made from natural renewable resources such as new and/or recycled vegetable oils and
animal fats. Biodiesel does not contain petroleum, but it can be blended with petroleum diesel to create a fuel mixture such as B20, which is a blend of 20 percent biodiesel and 80 percent regular petroleum diesel.

B20 biodiesel has been shown to substantially reduce emissions levels of carbon monoxide, particulate matter, and unburned hydrocarbons, which are a contributing factor to the formation of ozone and smog. Tests also show that biodiesel produces significantly lower emissions of sulfates (a major component of acid rain), as well as PAH (polycyclic aromatic hydrocarbons) and nitrated PAH compounds, which have been identified as potential cancer-causing compounds.

Biodiesel provides a cleaner-burning alternative fuel for school and transit buses, farm equipment, refuse haulers and other heavy-duty or fleet vehicles. Biodiesel is domestically produced; its use helps reduce the nation’s dependence on imported oil and can help boost the agricultural sector of the economy.

National Model

Denver’s Green Fleet policy has served as a model for several other cities, both nationally and internationally. The program has been adopted by the International Council of Local Environmental Initiatives (ICLEI) as part of its Cities for Climate Protection Campaign as an effective program to decrease vehicle emissions, and promoted by the American Council for an Energy Efficient Economy (ACEEE).

The city’s central fleet maintenance operations have also garnered national recognition. In 2005, Denver was awarded 8th place out of 93,000 fleets on Fleet Equipment Magazine’s list of the 100 Best Fleets in North America. In 2008 Denver received the recognition of 9th place for Green Fleets in North America, and in 2009 the City received 2nd place status of Green Fleets in North America.

Vehicle Tally

The City of Denver maintains a central fleet of 2,681 vehicles co-managed by the Public Works and Safety Departments, and a satellite fleet of 872 vehicles at Denver International Airport, for a total fleet of 3,533 vehicles. Every vehicle purchased by the City is either a hybrid or the most fuel efficient vehicle for the job. Here’s the breakdown to date of alternative fuels and technologies being used:

Hybrids: 138
Compressed Natural Gas (CNG): 136
Gasoline/CNG Dual Fuel: 103
B20 Biodiesel: 1,041
Propane: 29
Electric: 74

IN-DEPTH:

• View Denver’s Green Fleet executive orders.
• Learn more about ICLEI’s Green Fleets program.
• Locate a Colorado biodiesel retail site.
• Find other alternative fuel stations in Denver.
• Read more about alternative fuels and vehicles.