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Is ‘renewable diesel’ an alternative to fossil fuel?

As an ocean research scientist, Bruce Appelgate thought it best to start going green at home, on one of Scripps Institution of Oceanography’s research vessels. Appelgate, the San Diego institution’s associate director, decided to run the 125-foot Robert Gordon Sproul on 100 percent “renewable diesel” fuel from September 2014 to December 2015, a period when the Sproul undertook 39 research and educational missions, put in 89 operational days at sea and covered 14,400 miles.

The research vessel Robert Gordon Sproul used 52,500 gallons of renewable biofuel over one year and ran as well, if not better, than ever.

Though renewable diesel is made from non-food-grade vegetable oils and waste fat from foods, fish and slaughterhouses, it isn’t technically a biofuel because it is “hydrotreated” — cracked with hydrogen, which removes the oxygen in it — so its chemical makeup is nearly identical to that of petroleum-based marine diesel.

The beauty of renewable diesel is it can be burned “neat,” with no fossil fuel added, or in any mix with fossil fuel, and no engine alterations are necessary. “You put it in the tank, don’t do anything to the engine or fuel system, and it runs,” Appelgate says.

That might look good on paper, but how about in the real world? “The whole point of this was for someone to stick his neck out and give this an honest test.” Appelgate says there was very little risk in testing the fuel on the Sproul’s twin 675-hp 12V-149 Detroit diesels. “We took this on ourselves after looking at it very carefully,” he says.

Scripps isn’t the first big user to give renewable fuel a try. “The U.S. Navy has a pretty solid history in testing these kinds of fuels,” Appelgate says. “They have a strategic interest in this.” He says the Navy has run several “green fleet” exercises using a product similar to the one Scripps used, but in a 50-50 blend.

“They wanted to show they could use it,” he says. “There were no ill effects [on the ships’ engines].”

Last July, United Parcel Service contracted with Finnish refiner Neste Oil — the supplier of Sproul’s fuel — to buy 46 million gallons of renewable diesel over three years after testing it in its trucks. UPS wants it to replace 12 percent of the petroleum-based diesel it uses by 2017.

Also, FedEx has signed a seven-year contract with Red Rock Biofuels of Lakeview, Oregon, to supply 48 million gallons of a similar “synthetic renewable crude” made from combustible materials from the forest floor to mix 50-50 with jet fuel for its aircraft.

The Sproul burned 52,500 gallons of 100 percent renewable diesel during the test. Emissions of NOx — nitrogen oxides, which contribute to smog and acid rain — were about 13 percent lower than with petroleum-based marine fuel, especially at lower rpm levels, Appelgate says. Particle emissions, however, were 35 percent higher for the renewable diesel, especially when the engine was running at higher speeds, and black carbon or soot counts were slightly higher, as well.

Yet Appelgate thinks renewable diesel still is a winner. Its greatest benefit, if it is made mainly from processed vegetable waste, is that the plant material absorbs carbon dioxide from the air while it is growing, so even though it throws carbon dioxide back into the air when it burns as a fuel, it is in the end close to carbon neutral, he says.

“The important thing about this is it can be sustainably and renewably produced using vegetable material,” he says. It costs 10 percent more than petroleum diesel, but Appelgate says the price would fall if it were produced locally.

He says the Sproul ran as well if not slightly better on the green fuel than on petroleum diesel. He plans to continue using renewable diesel so long as he can offset the 10 percent cost differential by buying it in volume at a depot near San Francisco.

One of Scripps’ missions is to become more carbon neutral, but like many cost-conscious vessel operators, the institution can’t typically justify spending more for fuel than is absolutely necessary to those who award its research grants. “We’re bound to provide the best value for the money we receive,” he says.

In addition to the Sproul, Scripps operates the 273-foot Roger Revelle and 238-foot Sally Ride. The Sproul typically operates close to home, where it can easily refuel with renewable diesel. The other two research vessels work globally, sometimes staying abroad for seven years at a time, so they must operate on petroleum diesel. “Sourcing this [renewable] fuel in foreign ports is impossible,” Appelgate says.

San Diego is home to a “vibrant maritime community,” he says. “The Navy has a strong presence here. We’ve got a huge recreational boating community — sail and power — a big charter fishing fleet, harbor craft.” There are outlets for Neste-produced renewable energy (Propel Fuels) in California, but Appelgate says it’s still not widely enough available to be a reliable replacement for petroleum diesel. San Diego alone probably would need 1 million gallons a year just to serve commercial operators, he says.

Appelgate is advocating more production of renewable diesel from algae, which a small company in San Francisco is doing. “We could grow the algae in brackish water, even in the desert, if we wanted to,” he says. Locally grown algae would be a reliable feedstock for the fuel and wouldn’t be taking food off people’s tables.

John McKnight, the National Marine Manufacturers Association’s fuel guru, says the NMMA worked with the Department of Energy, the American Boat & Yacht Council and OEM engineers for five years to test and validate biobutanol — a renewable fuel made from biomass — to replace ethanol in gasoline blends for marine engines. Unlike ethanol, it wouldn’t cause engine damage in a 15 percent blend with gasoline. But he says biobutanol is not widely available because it costs more than ethanol.

NMMA hasn’t yet investigated renewable diesel, McKnight says, but marine engine manufacturers have tested and validated the use of diesel blends containing 5 to 20 percent biodiesel — fuel made from vegetable oils, animal fats or recycled restaurant grease.

McKnight says the NMMA began its inquiries into biobutanol at a time when gasoline prices were topping $4 a gallon and oil supplies in the Middle East were in jeopardy. “We were in a different world then, importing most of our oil,” he says.

With shale oil discoveries in Wyoming, Colorado, North Dakota and Texas, the United States has become an oil exporter, and oil prices have fallen by almost half. The financial incentive for using renewable fuels isn’t as great now, but Appelgate says the environmental incentive remains strong to reduce the production of greenhouse gases and slow global warming. He is seeing a few Californians using the locally available renewable diesel in their diesel-powered cars and boats. “It’s catching on, but we’re not there yet,” he says. “We’ve shown that it works.”

This article originally appeared in the September 2016 issue.