Seventh Update on the Houston Area Problem Fuels


Taking a holistic view of the contamination and its effects, we are able to see 2 possibilities

Contamination from Tall oil

We obtained a Crude Tall Oil (CTO) sample from the market and analyzed it. We noted abietic acid and pimaric acid (the main culprit in providing the adhesive property) and about 4,400 ppm of alpha pinene. We have looked for common abnormalities in 6 different fuel samples bunkered in Houston area which caused machinery problems. In these 6 samples we were able to see High acidity (high TAN) and presence of alpha pinene. The tests to establish the presence of other acids is going on. Increasingly, the evidence is pointing towards the presence of tall oil in these samples.

Contamination from biodiesel waste

We often find biodiesel waste (off spec biodiesel) in bunker fuels. Tests of these bunkers indicate high FAME’s (Fatty Acid Methyl Esters) and sometimes other acids. We have noted high FAME’s and acids in the 6 problem samples referred to above.

The question arises if there are 2 streams of contaminants / adulterants in these fuels. The answer is no.

The reason is that Tall oil itself is used for manufacturing Biodiesel and off spec biodiesel from this process could contain all the substances listed above.

In fact, there is at least one plant in Houston which is producing biodiesel using Tall oil.

It is stated that there is a supply potential of 2.6 MMT for Crude Tall Oil (CTO) of which 1.75 MMT is currently being used, leaving the balance available for other purposes. Of this balance, 0.23 MMT of CTO is used for Biodiesel manufacture.

It can be seen from above that all the evidence is pointing to off‐spec biodiesel produced using tall oil and the waste from this process is likely to be the substance added to the bunker fuel as cutter stock.


This off spec material is of low viscosity. The measured viscosity of the CTO was 86 CST. It is available at a very low cost and therefore lends itself to use as a low‐cost cutter stock.


We still need to confirm that the bunker fuel samples contain other acids which are likely to cause the adhesion. Once these tests are completed, our investigation will be complete.

Thank you for your patience.

Best regards,

Dr. Vis

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