When biodiesel is poorly made—often referred to as “bad biodiesel”—one of the biggest red flags is a high concentration of glycerine (or glycerin/glycerol). Here’s why that matters:
What Glycerine Is in Biodiesel
• Glycerine is a byproduct of the transesterification process used to make biodiesel from fats or oils.
• Ideally, it should be separated and removed during production.
• If not properly removed, it remains in the fuel as free glycerine or bound glycerides (mono-, di-, or triglycerides).
Why High Glycerine Is a Problem
• Engine Damage: Excess glycerine can clog fuel injectors, form deposits on pistons and valves, and lead to poor combustion.
• Cold Weather Issues: Glycerine solidifies at relatively high temperatures, which can cause fuel gelling and blockages in cold climates.
• Storage Instability: Glycerine can separate out over time, reducing shelf life and causing sediment in tanks.
• Fails Standards: High glycerine levels mean the fuel doesn’t meet ASTM D6751 or EN 14214 standards, making it unsuitable for commercial use.
How It’s Measured
• Standards like ASTM D6584 and EN 14105 use gas chromatography to measure both free and total glycerine in biodiesel.
• Acceptable limits are very low—typically <0.02% for free glycerine and <0.24% for total glycerine in B100 biodiesel.
Can It Be Fixed?
• Yes, but it requires reprocessing or purification, such as:
• Washing the biodiesel to remove impurities
• Vacuum distillation
• Membrane filtration or electrodialysis for crude glycerine recovery
Contact www.dieselcraft.com for a fuel purifier and centrifuge to fix the problem.

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