U-Idaho Biodiesel Education U-Idaho College of Agricultural and Life Sciences Image Map
Jun 042012

By Joe Thompson, Biodiesel Lab Manager (Posted on June 04, 2012)

A commenter on a previous blog post (Engines and Vehicles Testing – see below) asked us about our work on biodiesel use in ferries.

In 2008 the Puget Sound Clean Air Agency was awarded a Department of Energy grant to study the problem of sludge formation found in the fuel systems of Washington State Ferries (WSF) vessels using biodiesel. The project team assembled to solve this problem was: Washington State University, The University of Idaho, The Glosten Associates, and Imperium Renewables. Other contributors include: GenX Energy, the Renewable Energy Group, and Seattle based fuel blender and suppliers Sound Refining and Rainier Petroleum. The team formulated a research plan and executed the study and demonstration project over a two-year period (2008-2009).

Issaquah ferry

Issaquah ferry in operation

The results of this project showed that biodiesel can successfully be used in ferries with the application of a biocide to kill bacteria that tend to grow in biodiesel used in marine environments.

Washington State Ferries’ Current Biodiesel Use

Currently, the Washington State Ferry system burns a B5 biodiesel blend in 17 of their vessels. Five additional vessels will begin to use a B5 blend in late September of this year. Paul Brodeur, Director of Vessel Maintenance, Preservation, and Engineering, hopes that WSF use of biodiesel serves to show other fleets that “it’s not an insurmountable task. This is doable if you take the right steps.”

Within the next four months, the Washington State Ferries system will begin to implement a mandate that 51% of their biodiesel must come from in-state sources. Currently, they use biodiesel made from canola, camelina, and waste vegetable oil sourced in Washington state, and soy biodiesel from the Midwest.

Brodeur hopes to use higher blends of biodiesel in the future if funding from the state legislature becomes available.

Why Use Biodiesel in Ferries?

The Washington State Ferries consume about 18 million gallons of diesel fuel per year. Diesel particulate emissions are a significant health risk in the Puget Sound region. According to the Environmental Protection Agency, using a B20 blend instead of straight petro-diesel would reduce diesel particulate emissions by 10% and carbon monoxide by 11% (p. 3, Washington State Ferry Biodiesel Research and Demonstration Project Full Report). According to Brodeur, the energy security benefits of biodiesel are also important to the Washington State Ferry system.

Purpose of the Study

The Washington State Ferry Biodiesel Research and Demonstration Project aimed to clarify how biodiesel blends should be tested and handled for successful use in ferries. During a pilot test conducted by the Washington State Ferries system in 2004, B20 was found to form sludge that clogged the ferries’ fuel purifiers and fuel filters. The cause of this sludge formation was unclear. The 2008 project aimed to test the fuel and evaluate the fuel handling in order to determine the causes, and to propose solutions, to this problem.

Vessels Used in Project

Biodiesel blends were tested in:

  • M/V Tillikum, a 310-foot ferry with two Electro Motive Diesel engines, which can carry 1200 passengers and 87 autos. This vessel was tested with canola biodiesel processed via distillation to ensure a low content of minor compounds that could lead to precipitates.
  • M/V Klahowya, a 310-foot ferry with two Electro Motive Diesel engines, which can carry 800 passengers and 87 autos. This vessel was tested with soy biodiesel.
  • M/V Issaquah, a 329-foot ferry with two General Electric diesel engines, which can carry 1200 passengers and 124 autos. This vessel was tested with high cloud point biodiesel.

In all the above vessels, fuel is stored in large integral hull tanks. From here, the fuel is pumped through a centrifuge to remove water and particulates, and then into day tanks. Before entering the engine from the day tanks, the fuel is filtered to remove particulates.

Why did the sludge form?

During the 2004 trial, the sludge was variously described as a “milky white gelatinous substance,” “butterscotch mousse,” and “black grainy material with a grease-like texture.”

A literature review revealed that the sludge could be caused by oxidation, water in the biodiesel (which can lead to bacterial growth), gelling of the biodiesel due to low temperatures, sterol glucosides or other precipitates that can form under low temperatures, and/or impurities due to incomplete fuel tank cleaning.

At the University of Idaho Biodiesel Lab, we attempted to form sludge by duplicating conditions that might be found in a ferry fuel system. For example, we added varying amounts of water, iron oxide, salt, soap, and dye to batches of biodiesel. These mixtures were then tested at varying temperatures. However, we were not able to produce sludge similar to that found on the ferries in 2004.

Therefore, since we didn’t know the exact cause of the sludge formation, during the 2008 trial, the main goal was to try to prevent the sludge from forming, and to figure out how to deal with the sludge effectively if it did form again.

Preventing Sludge Formation

The researchers’ recommendations at the start of the tests were:

  • The entire fuel system must be thoroughly cleaned before adding biodiesel blends.
  • Biodiesel used in the 2008 test must pass the Cold Soak Filtration Test to make sure the biodiesel will not form precipitates at low temperatures.
  • In each vehicle, the testing should start with B5. Increasing percentages of biodiesel should be tested at intervals of four weeks.
  • B20 must be treated with a biocide to prevent microbial growth, and the fuel must be tested for microbes during fueling.

The Issaquah ran without problems on B5 and B10. Filters became clogged with B20, but the problem was solved with the addition of a biocide to the fuel. The Tillikum experienced sludge buildup with B5, and the problem was solved with the application of the biocide. Because of these experiences, biocide was added to the fuel from the start with the Klahowya.

Ferry sludgeThe photo at left shows sludge under a microscope. Active bacteria are the blue rods and dots.


The researchers concluded:

  • Microbial growth turned out to be the major cause of sludge formation.
  • Type of feedstock had no effect on fuel quality or sludge formation.
  • The percentage of biodiesel (B5 to B20) had no effect on vessel operations or maintenance.
  • Fuel tanks and lines should be thoroughly cleaned before using biodiesel blends.
  • Adding a biocide to the biodiesel blend prevented the sludge formation.
For More Information

For the complete report on the Washington State Ferries Biodiesel Research and Demonstration Project, visit this link: http://www.wsdot.wa.gov/Ferries/Environment/biodiesel.htm

For information about other marine vessels using biodiesel, visit this link to an article from June 2011 in Biodiesel Magazine: http://www.biodieselmagazine.com/articles/7858/biodiesel-sets-sail

 June 4, 2012  Add comments
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