STORY Commercial Marine

HVO makes the difference

Posted on July 27, 2023 by Jonathan Rowland

Since 1 January 2023, it has been mandatory for commercial harbor craft operating in Californian waters to run on HVO instead of fossil diesel. The Golden Gate Ferrys in San Francico have been pioneering the use of HVO, also known as renewable diesel, since May 2019. A field report.
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Operated by the Golden Gate Bridge, Highway & Transportation District, the Golden Gate Ferry began service in 1970 between San Francisco and Sausalito to the north. Today, the district operates six routes around the San Francisco Bay area. All of its vessels are equipped with mtu engines.

Since switching to HVO, the operator has enjoyed cleaner-running engines: a fact that was apparent almost immediately to those onboard. “The most obvious visible impact was the lack of black smoke coming from the engines when the vessel was coming up to speed or ramping up under load,” said Michael Hoffman, Deputy General Manager at Golden Gate Bridge, Highway & Transportation District.

That’s because HVO – which stands for hydrotreated vegetable oil – has significantly lower particulate matter (PM) emissions than fossil diesels. This reduction in PM is a key aim of the regulations that now mandate the use of HVO in California, where is it known as R99. Introduced by the California Air Resources Board (CARB), the new rules aim to reduce the health risks associated with airborne pollutants and ensure that commercial harbor craft do not create excess visible emissions.  

“Besides the significantly lower CO2 emissions, lowering PM emitted into our air is one of the key benefits of using R99,” continued Hoffman. “In San Francisco, these emissions have a particular impact on at-risk and disadvantaged communities. By switching to R99, we are therefore able to improve our environmental stewardship and contribute to meeting health goals in these areas.”  

Since 2019, the Californian ferry operator Golden Gate Ferry has been operating its six ferries with the sustainable fuel HVO.

No impact on performance

HVO is a drop-in replacement for fossil diesels, providing similar performance without any adaptation needed to the engines or on-shore infrastructure. The 20 mtu Series 4000 engines operated by the Golden Gate Bridge, Highway & Transportation District on its six ferries have now run for more than 120,000   hours without issues.  

“We haven’t seen any difference in operating performance or maintenance requirements since switching from ultra-low sulfur diesel to R99 in our engines."

Michael Hoffman, Deputy General Manager at Golden Gate Bridge, Highway & Transportation District

That’s not to say there wasn’t some initial concern about the switch, as Hoffman explained:  
“When we first began using R99, we entered into a dialogue with Rolls-Royce’ Power Systems business unit. They initially did not accept the R99 on their approved fuels list. But they were interested in working with us to find out how R99 interacted with their engines, particularly the fuel system: low-pressure and high-pressure fuel pumps, fuel injectors, and fuel filter seals. As a result of these discussions, Rolls-Royce agreed to work with us, removing the identified fuel system components from a few of our vessels that had accumulated more than 3,000 hours on R99. These components were returned to the factory for further evaluation, as part of Rolls Royce Power Systems standard fuel release process. It was a very positive process for both companies.”  

What is renewable diesel?  

HVO is produced from waste vegetable and animal fats and used vegetable oils. These base materials are converted into hydrocarbons that can be used as a substitute for fossil fuels, such as diesel, via a catalytic reaction with hydrogen. The resulting fuel not only significantly lowers PM emissions by up to 80%; it reduces emissions of other harmful pollutants, including nitrogen oxides (NOX) by up to 8%.  

The use of HVO also reduces carbon emissions. Because the production, transportation, and combustion of renewable diesel only emits about as much carbon dioxide (CO2) as is absorbed by the biomass base materials during growth, the use of renewable diesel results in a significant reduction in carbon footprint. CO2 emissions can be reduced by up to 90% compared to traditional fossil diesels. Renewable diesel thus has significant implications for the decarbonization of hard-to-abate sectors, such as the marine industry.  

A final – but important – benefit to note is that the production of renewable diesel doesn’t compete with food production, because it relies only on waste and residual biomass as base materials.  

Benefits of HVO

  • HVO is already available to buy.  
  • As HVO is a drop-in fuel, no adjustments are necessary for most diesel engines that are approved for HVO use. It is advisable however, to check elastomer seals regularly in the first four weeks following a switchover to HVO.  
  • The storage stability of pure HVO is substantially higher than that of pure Fatty Acid Methyl Ester (FAME) biodiesel, or HVO / FAME mixtures, and even fossil diesel fuel B7. That makes HVO particularly attractive to operators of standby power systems.
  • Our tests have confirmed that there are usually no differences in the released mtu common rail engines in terms of their maximum power, load acceptance and fuel consumption - regardless of whether they are fuelled with HVO or diesel.
  • Depending on the fuel manufacturing process, CO2 emissions fall by up to 90%. Particulate emissions fall by over 40%. Nitrogen oxide emissions are up to 8% lower.  

See the difference

Gold Gate Ferry may have blazed a trail but, thanks to the new CARB regulations, California is now a hub for HVO. Other Rolls-Royce Power Systems customers in the region have also made the switch, including the Catalina Express, Catalina Flyer and the San Francisco Bay Area Water Emergency Transportation Authority (WETA). Seattle-based Foss Maritime is also now using renewable diesel in its vessels operating in California.

It is all part of a move in the marine industry to reduce emissions. Many of these efforts can go unnoticed, however, as they lack a visual element. “It’s hard for the general public to see the difference between a Tier 3 and Tier 4 engine,” concluded Hoffman. “But when we have boats emitting black smoke one day and not the next, that’s an excellent result. And that’s what we got when we switched to R99. We could clearly visualize the impact this cleaner fuel was having on the environment and air quality.”  

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