The Triton

Engine Room

Biodiesel and petrodiesel may be in your yacht’s future


“I have never had a large yacht request biodiesel,” Larry Lawrence said. “Most yachts would not want to use straight biodiesel due to microbe and water issues.”

Lawrence should know. He is the marine services director at Port Consolidated in Ft. Lauderdale, a supplier of high quality motor fuels in Florida.

With all the buzz about green superyachts over the past few years, it is surprising that large yachts in South Florida are not using biodiesel, a renewable energy resource made right here in the U.S. of A. Perhaps myths and anecdotes about biodiesel are cluttering the conversation and its acceptance.

Simply stated, biodiesel is a renewable alternative to petroleum-based diesel fuel. It can be made from any plant oil, animal oil, or even used cooking oil. In the United States about 90 percent of biodiesel is made from soybean oil with beans grown expressly for that purpose.

Biodiesel is not refined like petroleum diesel. Instead, it is produced by a chemical process called transesterification. This process combines the fatty acids in soybean oil with alcohol to produce methyl esters, the chemical name for biodiesel.

This straight biodiesel is subject to standards that determine its fuel grade in much the same way that diesel cracked from petroleum is graded. The American Society for Testing and Materials (ASTM) uses the D975 standard to determine whether a batch of diesel oil can be used as engine fuel or relegated to heating oil. The ASTM D6751 is the primary standard for biodiesel. In order to be considered a reliable engine fuel, biodiesel must pass the battery of tests outlined in D6751.

Straight biodiesel (also known as “neat”, just like a pour of straight bourbon) is 100 percent biodiesel. Neat biodiesel or B100 is seldom used as fuel since few engine manufacturers will warrant their engine components if run on B100.

However, biodiesel blended with petrodiesel is used successfully to operate marine engines. The percentage of biodiesel to petrodiesel in the blend is represented by the number in the notation, e.g., B20 is a blend of 20 percent biodiesel and 80 percent petrodiesel by volume.

Cummins, which manufactures marine engines up to about 700 hp, approves the use of B20 biodiesel on many of its high horsepower products that are fitted with common rail fuel injection systems. For larger engines with the horsepower needed for superyachts, manufacturers such as MTU allow their engines to be run on a maximum of B07 (7 percent biodiesel). MTU’s intention is to have its newer engine designs run on B100.

Caterpillar engines, on the other hand, can now operate with B20 on its complete line of marine engines. In Europe, MAN common rail engines are certified to run on B05. However, in the United States MAN will not approve the use of biodiesel blends on its common rail engines. Stateside, its engineers will only allow the use of these blends in older, non-common rail engines. The reason? MAN believes the quality of biodiesel manufactured in Europe is more consistent than in the U.S., but they do believe that will change.

Biodiesel blends, which are approved for use in marine engines, have at least one advantage over petrodiesel. Biodiesel has a higher lubricity, which results in less wear to parts such as fuel injectors. Traditional diesel fuel uses sulfur for lubrication, and much of that component has been removed from the refined fuel to reduce emissions and the resulting air pollution.

There are two disadvantages of blended biodiesel. The first is that it degrades three times faster than petroleum-based diesel, so proper fuel handling and storage techniques must be adhered to.

The other drawback is that biodiesel acts as a solvent and will dissolve or loosen many of the gum and tar deposits in the fuel system, which will cause the fuel filters to clog up. It is recommended when converting from petrodiesel to a biodiesel blend that fuel filters be changed more frequently until all the petrodiesel deposits are cleaned out.

Whether using a biodiesel blend or petrodiesel, a fuel preventive maintenance program is a must. Use of the proper fuel additives, regularly scheduled fuel polishing, and tank cleaning will assure that either type fuel is clear, bright and within specifications.

But using a biodiesel blend will make a statement about your yacht’s commitment to the marine environment. It can be the first step in becoming a “green” yacht, which will help assure the seas we cruise will be enjoyed for many generations to come.

Capt. Jeff Werner has been in yachting for more than 20 years on private and charter yachts, both sail and power. He is an instructor for RYA, MCA, USCG and US Sailing courses and owns Diesel Doctor ( Comments on this column are welcome at

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