Calcium and Magnesium may form abrasive solids or be present as soluble metallic soaps. If present as solids, excessive injector, fuel pump, piston, and ring wear may result. Soluble metallic soaps may contribute to filter plugging and engine deposits. High levels of these elements may accumulate in exhaust particulate removal devices and may increase back pressure that may require shorter maintenance intervals. Calcium and Magnesium analysis is performed in accordance with EN 14538.
ASTM D6751 Requirement: a maximum of 5ppm (wt/wt) combined calcium and magnesium content.
As a fuel oxidizes, it may form organic acids and polymers that may cause fuel system deposits, fuel filter clogging, and fuel system malfunctions. Once auto-oxidation of the fuel begins, there is no way to reverse the effects. Although continued acid formation cannot be stopped, the process may be slowed by the addition of anti-oxidants. Oxidation Stability is performed in accordance with EN 15751.
ASTM D6751 Requirement: a minimum oxidative stability of 3 hours.
The content of water in petroleum products plays an important role in predicting quality and performance of the product. If moisture is present, premature corrosion and wear, diminished lubrication, filter plugging, decreased effectiveness of additives, and bacterial growth may ensue. Dissolved (entrained) water, not detectable by the human eye, is measured by ASTM D6304, Coulometric Karl Fischer Determination. This test method is applicable to moisture concentrations as low as 10mg/kg.
ASTM D6751 Requirement: None. However, many distributors require 500ppm or less.
The Cold Soak Filtration Test (CSFT) is intended to assess the presence of impurities that may precipitate from fuel above the cloud point and cause filter plugging. The test is designed to accelerate precipitate formation. Short filtration times indicate the absence of substances that are likely to cause filter pugging at temperatures above the cloud point. Generally, B100 with low CSFT results and blends made from the B100 will perform well down to the cloud point. CSFT is performed in accordance with ASTM D7501.
ASTM D6751 Requirement: a maximum filtration time of 360 seconds. There is a maximum filtration time of 200 seconds to qualify as a Grade No. 1B biodiesel (a maximum Monoglyceride content of 0.40% mass as well as passing results for the remaining ASTM D6751 analyses is required for a No. 1B designation).
Sulfur content impacts engine wear, creates deposits, and may affect emissions control system performance. The effects vary with operating conditions. The Environmental Protection Agency (EPA) has imposed limits on sulfur emissions for environmental reasons and ultra-low sulfur fuels are preferred. B100 contains low quantities of sulfur. Sulfur is analyzed in accordance with ASTM D5453. Gorge Analytical, LLC is EPA-approved for the analysis of low-sulfur and ultra-low sulfur diesel. Visit our Quality Assurance page for more information.
ASTM D6751 Requirement: a maximum sulfur content of 15ppm for Grade S15 and 500ppm for Grade S500.
Visual Inspection is a standardized test that supports the requirement that fuel is clear and bright and free of visible particulate matter. Biodiesel fuels with these physical qualities will increase the confidence of distributors and end-users.
ASTM D6751 Requirement: Visually free of water, sediment, and suspended solids.
Water and Sediment is determined in accordance with ASTM D2709. The method requires the use of a centrifuge to separate free water and sediment from the fuel. Free water may be detected visually as a “hazy” appearance if gross contamination is present. Gross water contamination can lead to storage tank corrosion and provides an environment conducive to microbial growth. Water and sediment contamination may also be responsible for filter plugging and poor aerosol nebulization in fuel oil systems. Gross water contamination is more frequently observed during fuel storage rather than fuel production.
ASTM D6751 Requirement: a maximum for water and sediment of 0.050% by volume.
A fuel property that is particularly important for the low temperature operability of biodiesel fuel is the cloud point, defined as the temperature at which crystals are observed to precipitate from the fuel. Therefore, it is an index of the lowest temperature of the fuel’s usability for certain applications. Operating at temperatures below the cloud point of a biodiesel fuel can result in fuel filter clogging due to the wax crystals. Cloud point determination is also useful information for blending purposes. Cloud point analysis is performed in accordance with ASTM D2500.
ASTM D6751 Requirement: None. Report Only.
The Total Acid Number (TAN) is a sum parameter for all acidic components to indicate the level of free fatty acids (FFA) and process acids present in biodiesel as well as organic acids that may be created over time as the fuel ages and oxidizes. TAN analysis is performed in accordance with ASTM D664 which requires potentiometric determination of the titration endpoint. High acid numbers have been linked to fueling system deposits and corrosion.
ASTM D6751 Requirement: a maximum total acid number of 0.50 mg KOH/g.
Flash Point is defined as the lowest temperature at which vapors of a material will ignite upon application of an ignition source. The test is conducted under specific test conditions in accordance with ASTM D93. Determination of the flash point is important for the safe handling, storage, and transportation of liquid fuels. Although biodiesel is generally non-hazardous, inadequate methanol recovery during the biodiesel production process will result in a low flash point.
ASTM D6751 Requirement: minimum 93°C. If the flash point is less than 130°C (but greater than 93°C), then methanol recovery must be demonstrated by headspace gas chromatography in accordance with EN 14110.