The City of San Francisco will phase out the use of petroleum diesel in its municipal fleet and replace it with renewable diesel by the end of this year, Mayor Ed Lee announced at a conference in Vatican City on climate change.

“By changing our fleet’s fuel from petroleum to renewable diesel, we’re taking action that is good for the global climate, and at the same time promotes environmental justice in our community by leading to cleaner, healthier air for some of our most vulnerable neighborhoods,” said Mayor Lee.

San Francisco's switch to renewable diesel is expected to slash greenhouse gas emissions from diesel vehicles by more than 60 percent, according to a release from the mayor's office. Using renewable diesel is also designed to reduce the emissions of soot and other air quality pollutants that harm the health of local residents, and which disproportionately hurt San Francisco’s low-income communities because so much of the heavy-duty vehicle traffic occurs in and near those communities, the release added.

“The [San Francisco Fire Department] piloted the use of renewable diesel fuel for our fleet over a period of six months last year,” said Fire Chief Joanne Hayes-White. “Our fleet ran cleaner and more efficiently, and we are completely supportive of the Mayor’s call to switch to renewable diesel to improve the environment and create a healthier future for our residents.”

San Francisco began using cleaner forms of diesel fuel a half-dozen years ago by transitioning from petroleum diesel to a blend of biodiesel, according to the release. Currently, most of the municipal fleet uses B-20, which is 20 percent biodiesel and 80 percent petroleum diesel.

Although renewable diesel is currently more expensive to produce, it qualifies for credits under federal and state programs, allowing renewable diesel to be available at or below the price of conventional petroleum diesel.

As with biodiesel, renewable diesel is produced from numerous bio-feedstock sources, including fats, oils, and greases. However, renewable diesel is produced through a hydrogenation process, while biodiesel uses an esterification process.

The full lifecycle emissions of carbon from renewable diesel produced from sustainable sources are more than 60 percent lower than either petroleum or B-20 biodiesel, according to the California Air Resources Board. Chemically, renewable diesel is indistinguishable from petroleum diesel, and testing has shown it to have engine performance that matches or outperforms both petroleum diesel and biodiesel.