It's Not That Easy Greening Your Fleet

"The City of Austin is trying to make its fleet of more than 4,400 vehicles "carbon neutral" by 2020, a goal set in Mayor Will Wynn's Climate Protection Plan that requires a mix of more efficient and cleaner-burning fuels.

Carbon-neutral plans involve reducing carbon emissions through various steps and offsetting the remainder through other activities, such as planting trees, which absorb carbon in the air.

The city has spent more than $8 million since 2007 to convert and replace traditional vehicles and fuel stations and is about halfway through the process. The fleet now includes six garbage trucks that run on compressed natural gas, 248 vehicles that can use E85 - a blend of 15 percent gasoline and 85 percent ethanol - 271 propane-powered vehicles and 151 hybrids, mostly Toyota Priuses and Ford Escape sport-utility vehicles.

Austin isn't the only city rethinking the types of vehicles and fuels its fleet uses. Dozens of municipalities across the country, including Portland, Ore., and Dallas, have started building "green fleets."