A Concern With Biodiesel

Fuel quality control veteran outlines issues related to transport of emerging fuels

It is said that a writer should get the point across within the first sentence or two, so I will: While the industry focus has been primarily on pipelines, anyone who purchases aviation fuel that is delivered by road transport tanker truck that is not ‘grade dedicated’ should read this article very carefully. A recent Joint Inspection Group (JIG) bulletin states, “Jet fuel has been transported in multi-product pipelines for decades. The practice represents an efficient, practical, and environmentally sound option for transporting large volumes of jet fuel over long distances. Quality assurance procedures for handling interfaces between products together with laboratory testing requirements are well established and quality incidents are rare. The introduction of biodiesel into many countries, either by government mandate or customer demand, is challenging this status quo.”

The main issue is that the bio component in biodiesel called FAME (Fatty Acid Methyl Ester) is a surface-active material. In theory, FAME can stick to pipe walls as the biodiesel passes; it then can be removed from the wall and into the fuel grade that follows in the pipeline (which can be jet fuel).

FAME is made from a variety of plant oils (rape, soy, palm, and coconut) and animal fat or tallow. FAME is added to diesel fuel to produce biodiesel and is typically blended in percent quantities at the refinery. Diesel fuel with 2 percent FAME is often called B2; with 5 percent, it is B5; and so on. FAME is added to diesel fuel to comply with renewable fuel mandates that are starting to be imposed across the country as a way to reduce greenhouse gas emissions. FAME is a “non–hydrocarbon” fuel component. The jet fuel specification states that only hydrocarbon components and approved additives are allowed.

FAA Issues a Bulletin
On May 1, 2009 FAA issued a Special Airworthiness Information Bulletin (SAIB: NE-09-25). The bulletin recommends that owners and operators of turbine-engine powered aircraft contact their fuel suppliers to verify they have implemented quality control and inspection procedures to ensure the fuel they deliver does not contain more than 5 ppm of FAME.

In part this FAA bulletin reads:

“The bio-component in biodiesel, FAME, is a surface-active material. This means that in theory, it can adhere to pipe and tank walls as the biodiesel passes through, and then release from the walls into the following product, which may be jet fuel. Also, small amounts of diesel containing FAME remaining within distribution manifolds, tanks, vehicles, and pipes can result in traces of FAME getting into jet fuel transported through the same components. At high enough concentrations, FAME can impact the thermal stability of the fuel that could lead to coke deposits in the fuel system. FAME contamination can also impact the freezing point of jet fuel resulting in gelling of the fuel. These conditions can result in engine operability problems, and possible engine flameout.” [Emphasis added.]

Acceptable level: 5 ppm
Pipeline common carriers are working closely with industry representatives in the United States and in Europe to develop procedures to prevent FAME contamination above the acceptable level of 5 parts per million (ppm). FAA’s SAIB states, “Jet fuel specifications are currently being updated to specify that levels of FAME in jet fuel below the detectable limit of 5 ppm are acceptable. Operation with jet fuel containing more than 5 ppm of FAME would not be in compliance with the aircraft and engine operating limitations, unless approved service information is issued with revised limitations to accommodate FAME levels greater than 5 ppm.”

In the U.K. and Europe, the co-transport of biodiesel and jet fuel in multi-product pipelines is common. So far in the U.S. this is not the case. While the risk of FAME contamination in multi-product pipelines in the U.S. may not be an issue today, government mandates and/or customer demand will likely cause biofuel volumes to grow, increasing the risk of FAME contamination.

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