The King County Department of Transportation (DOT) last week announced that the county’s water taxis are switching from conventional fuel to environmentally friendly biodiesel fuel.

“Using homegrown biodiesel, our water taxis have some of the cleanest-burning engines around,” King County Executive Dow Constantine said in a news release. “The use of biodiesel on the newest member of our fleet, the Sally Fox, will reduce particulates in the air and prevent more than 140 metric tons of carbon dioxide emissions every year.”

The Sally Fox, joined on Friday by a new vessel named the Doc Maynard, operates on a locally-sourced biodiesel blend, but also has environmental features ranging from more efficient engines to LED lights and recycling stations.

County DOT officials said that when the county’s third vessel, The Spirit of Kingston, has its annual maintenance this fall, the fuel tanks will be cleaned, readying the vessel to burn biodiesel.

The move allows the water taxi fleet to join the Washington State Ferries in operating some of the cleanest vessels in the nation.