Steamship Authority To Pilot Use Of Renewable Diesel Fuel This Summer

The Steamship Authority will test the use of a renewable diesel fuel on its largest vessel this summer, and the ferry operator stated it is expected to reduce its greenhouse gas emissions by at least half during operations.

The fuel, known as R99, is chemically the same as the ultra-low-sulfur marine diesel currently used by the Authority, but it is made of recently living biomass. It can be used interchangeably with traditional diesel fuel without the need for engine modifications, and it can be mixed with traditional diesel fuel without incident.

According to a “wheel-to-wheel” analysis of the fuel, which includes feedstock production and transportation, fuel production and distribution, and the use of the finished fuel emissions, R99 produces a minimum of 50 percent reduction in lifecycle greenhouse gas emissions and as much as 78 percent, depending on feedstock inputs.

While the fuel is newly available on the East Coast, it has long been in use on the West Coast to great success. General Manager Robert B. Davis stated that if the pilot program proves successful, the Authority will examine making the switch to R99 in all 10 of its ferries.

“We have heard excellent reports from other ferry operators about the use of R99 in their fleets, and we’re excited to be at the forefront of testing its use in New England,” Davis said. “This reduction in greenhouse gas emissions will be significant to our operations and our port communities.”

“This has the potential to be a real game-changer for us,” Chief Operating Officer Mark H. Amundsen said, noting that the manufacturers of all engines used in the Authority’s fleet have endorsed the use of R99.

At the May 15, 2025, joint meeting of the Steamship Authority Board and Port Council, the members unanimously authorized a $62,400 expenditure to cover the upcharge from ultra low-sulfur diesel fuel, for which the Authority currently pays approximately $2.40 per gallon, to R99, which was quoted at $2.99 per gallon, including delivery charges.

The trial will run from June 1 to September 1, 2025, aboard the M/V Island Home, which serves the Authority’s Woods Hole-Martha’s Vineyard route. Approximately 104,000 gallons of fuel are expected to be used during the test.

The Authority’s fuel supplier, Diesel Direct, will provide the fuel in a dedicated tanker to prevent the comingling of fuel supply.