2016- Journal of the American Oil Chemists Society, on-line link to the Springer journal article entitled: "Bias and Imprecision in the Determination of Free Glycerin in Biodiesel: The Unexpected Role of Limitations in Solubility" - https://link.springer.com/article/10.1007/s11746-016-2930-6.

NEW! 2021- Journal of the American Oil Chemists Society, on-line link to the Springer journal article entitled: "Solubility Limitations of Residual Steryl Glycosides, Saturated Monoglycerides and Glycerol in Commerical Biodiesel Fuels as Determinants of Filter Blockages": https://link.springer.com/article/10.1002/AOCS.12547.

The standard specifications ASTM D 6751 and EN 14214 specify limits that B100 fuels must meet. Biodiesel is derived from a variety of vegetable oil or animal fats that impart different temperature dependent properties that affect the flow, particularly at lower temperatures. Meeting the limits for practical cold weather use of biodiesel depends on feedstock and fuel quality.

Does your fuel meet the cold soak specifications of ASTM D6751? The cold soak test attempts to capture debris responsible for fuel filter blockages. The filters capture debris that remains after processing that is either insoluble or poorly soluble substances that collect on the cold soak filter may collect on vehicle fuel filters.

Biodiesel derived from soy and canola (or rape) tends to have better cold weather performance than fuel derived from animal fats such as lard and tallow. Currently, in addition to cloud point data which is essential for defining cold temperature limits of the bulk fuel, a cold soak filtration test is used to assess the magnitude of additional precipitates. The cold soak test appears to pick up room temperature insoluble impurities, such as sterol glucosides. However, the cold soak filterability test can fail to detect some cold weather limiting entities such as saturated monoglycerides, which represent a portion of the residual monoglycerides remaining after processing. At any particular total monoglyceride level, the saturate levels in rape or soy feedstocks are normally lower than those found in animal fats or palm. So, other variables being equal, particularly monoglyceride levels, a reduced risk for formation of insoluble saturated monoglycerides at low temperatures is also likely in fuels made from rape or soy. Because of day to day variations in pretreatment of feedstock and fuel processes these risks, though mitigated, may not eliminate the risk altogether.

Since 2006 we have we have made several private and public presentations on this subject (See About Us). People at these meetings discovered that during that widely publicized Minnesota winter fiasco of 2006, another lesser discussed episode of fuel filter blockages happened on the East coast. We have presented definitive lab data describing the composition of field fuel filter deposits from field incidents and the blended fuels from which the deposits originated. We have isolated contaminants from blended commercial fuels that have accumulated on filters. We offer a comprehensive package of analyses to define these deposits and determine their origin.

If you have an incident you would like us to investigate, keep in mind that fuel filter blockages above the cloud point are caused by any of a number of different substances that might result in the buildup of debris and the occlusion or "plugging" of filter pores. One or several substances may act in concert to collect on a filter matrix. These substances may or may not come from the biodiesel.

Improperly processed biofuel can contribute to, or cause fuel filter blockages. The agents causing blockages can originate from: feedstocks; an incomplete transesterification process; oxidation; transport; storage; interaction with engine or fuel system components. Petroleum diesel or ULSD and additives are also possible causes of filter blockages, clogging or plugging.

Key to finding the main culprit is a full analysis of the filter plugging incident. We can put our experience to work for you finding the cause of fuel filter blockages.

Deposits that form on filter surfaces could be caused by a number of different substances that can compromise fuel quality including sterol glucosides. Where do these deposits originate? Sterol glucosides start as an acylated form in unprocessed or partially processed seed oil. The transesterification process, the primary reaction used to form the methyl esters of biodiesel, causes a transformation of the AG to the sterol glucoside. Sterol glucosides are only slightly soluble in B100, whereas any remaining AG is relatively soluble. When deposits of sterol glucoside form in the fuel they can be transported throughout the fuel distribution network. Other types of substances can contribute to the formation of cold soak filter deposits.

You need a top-notch lab to help figure it all out. We can provide comprehensive fuel filter analysis services to get to the root cause. Also, take a look at our value added biodiesel testing services.

How well does your sterol glucoside removal process perform ? We have completed numerous evaluations and can provide the testing needed to validate the process.

Subscribe to our routine quality testing services or filter analysis packages and your $$$ will contribute to our research efforts to improve the processing and quality of biodiesel !

During the cold winter of 2006 a spate of blocked fuel filters involving biodiesel blends with petrodiesel struck several locations in the U.S. causing delays and frustrations at best. The most publicized of these events happened in Minnesota shortly after the implementation of a B2 mandate. Subsequently, similar reports have surfaced from many places in the world, typically cold spots in winter and but also in places that have experienced sudden unusual drops in temperature. We have studied fuel filter blockage incidents extensively, researched their causes, and have developed special procedures for comprehensive evaluations. We can perform these evaluations for you. Contact us for additional information on how to proceed.

There are generally two types of cold weather problems that are seen in the field. The first has to do with unobstructed flow of the main constituents of the bulk fuel, and the second is associated with fuel impurities that might impede flow through a filter. The bulk cold weather properties are generally adequately defined by cloud point and pour point measurements, tools developed long ago for the transportation industry. The second type, that associated with impurities in the fuel, has only recently had some attention. The causal impurities begin to have a dominant effect at temperatures well above the cloud or pour point. See our note below that discusses the role of impurities. These types of cold weather problems persist despite efforts to improve the character of the fuel by: implementing new standards; blending the B100 with petrodiesel; introducing additives to impede agglomeration; and various process purification schemes.

We have completed numerous investigations of fuel quality and filter plugging episodes associated with fleets of vehicles where we diagnose the problem and then assist a client in the creation of a satisfactory strategy for a solution. To find out more, give us a call at 717 299 6860 or send an email to: biodiesel@supersleuthchemists.com.

If you have a concern about these cold weather problems or have experienced them, we are prepared to work with you to: a) find the cause of the filter blockages; b) to devise a strategy that will minimize the possibility of a future experience.