Process        Inputs & Outputs

The Process

1. Purification—Any non-pure feedstock must be filtered to remove any remaining elements, such as food, dirt, or other organic materials. Water is also removed by heating the oil, above 120°C, or by using a drying agent, such as magnesium sulfate, to crystallize the water, which can be removed by re-filtering.
2. Titration—This step is done to neutralize (lower) the free fatty acids in the feedstock to move the pH between 8 and 9. This is achieved by adding catalyst on a sample level then mixing to the entire feedstock batch.
3. Catalyst Mixing—This step involves dissolving the catalyst into the alcohol.
4. Transesterification—This step mixes the feedstock with the catalyst mix in a heated environment (above the boiling point of alcohol, >50°C). The alcohol and triglyceride oils react in a way that rearranges molecules, resulting in methyl esters and glycerin.
5. Separation—In this step, the mixture settles to allow the crude biodiesel to be separated from the glycerin. This can be achieved by draining the heavier glycerin from the bottom of the tank or separating through a centrifuge.
6. Refining—This step washes the unreacted alcohol, catalyst and glycerin from the biodiesel. Traditionally this was achieved through water washing, which was done by spraying water over the crude biodiesel and letting the water settle in large settling tanks. Over time, the water would pull the impurities to the bottom of the pool leaving cleaned biodiesel on top. This process has numerous problems, including leaving too much water in the biodiesel, being too time consuming and adding to the cost of production by using a significant amount of water. Most companies now have developed some form of dry wash process, which can be done immediately, by introducing materials such as magnesium silicate powder, ion exchange resins, sulfuric acid and other powders into the mixture.
7. Distillation—The final step takes the biodiesel through distillation columns, which remove all final impurities, water and methanol, to produce ASTM 6571 quality B100. The recovered methanol can be reused in later production process runs.





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