WALNUT CREEK -- Walnut Creek has converted its diesel-powered vehicles to renewable diesel, a fuel even cleaner than traditional biodiesel, and says it is the first city in the nation to do so.

The switch to renewable diesel -- produced by a different chemical process than used to make regular biodiesel fuel -- will reduce the city's diesel emissions by more than 60 percent, lower its petroleum fuel needs by more than 20,000 gallons, and aid the city's campaign to cut greenhouse gas emissions, Fleet Supervisor Joe Jorgensen said in a news release.

Walnut Creek has 60 diesel powered vehicles and other equipment, such as street sweepers, dump trucks, tractors and mowers. All will take advantage of the new fuel.

Like traditional biodiesel, renewable diesel is produced from biological sources such as fats, oils and greases.

However, the renewable diesel production process makes it directly usable in any diesel engine without modification. Due to engine warranty limitations, traditional biodiesel must be blended with petroleum diesel.

Renewable diesel is more expensive to produce, said city spokeswoman Gayle Vassar, but federal and state credits make its consumer price the same or less than petroleum diesel.

Chemically, renewable diesel is indistinguishable from petroleum diesel, according to Pat O'Keefe, CEO of NEXGEN Fuel, which is producing the new fuel. O'Keefe is also vice president of Martinez-based Golden Gate Petroleum.

Walnut Creek's Climate Action Plan adopted in 2012 has a goal of reducing its greenhouse gas emissions to 15 percent below 2005 levels by the year 2020.

The city's top three sources of emissions in 2012 were transportation, residential, and commercial energy.