Biodiesel Production: A Step-by-Step Guide

• Biodiesel production involves a step-by-step process with raw material preparation, alcohol-catalyst mixing, transesterification, separation, and purification.

Raw Material Preparation

• Vegetable oil or animal fat is required at 1000g (1 liter).
• Methanol (CH₃OH) needed at 200g (0.2 liters, 20% of oil weight).
• A catalyst such as NaOH or KOH is needed at 5g (0.5% of oil weight).
• High free fatty acid (FFA) content (>2%) in the oil requires pre-treatment with acid esterification.
• Acid esterification involves reacting the oil with methanol and sulfuric acid (H₂SO₄) at 60°C for 60 minutes.
• Oil should be heated to 110°C for 30 minutes to remove any water content which can cause saponification.

Alcohol-Catalyst Mixing

• Methanol is needed at 200g (0.2 liters).
• Sodium hydroxide (NaOH) or potassium hydroxide (KOH) is required at 5g.
• The catalyst is added to the methanol and stirred until fully dissolved creating an exothermic reaction releasing heat.
• A sealed, non-reactive container (e.g., glass or stainless steel) should be used to avoid methanol evaporation.
• Proper ventilation is required as methanol fumes are toxic.

Transesterification Reaction

• Pre-heated vegetable oil is required at 1000g (1 liter).
• Methanol-catalyst mixture is added from the previous step.
• Oil is heated to 50–60°C, below methanol’s boiling point of 68°C.
• The methanol-catalyst mixture is slowly added while stirring continuously.
• Continuous stirring is needed at 700–1200 rpm for 60–90 minutes for the reaction to take place.
• The reaction formula is: Triglyceride + Methanol → Methyl Esters (Biodiesel) + Glycerin
• An example of the reaction is: (C₅₄H₁₀₀O₆) + 3 CH₃OH → 3 C₁₉H₃₄O₂ (Biodiesel) + C₃H₈O₃ (Glycerin)

Separation of Reaction Products

• Settling tank or separator is required.
• A centrifuge is optional for faster separation.
• The reaction mixture should settle for 8–24 hours in a settling tank, which allows heavier suspended particles to settle to the bottom due to gravity.
• The mixture separates this way into two layers.
• The top layer is Biodiesel (Fatty Acid Methyl Esters - FAME).
• The bottom layer is Glycerin, a byproduct of the reaction.
• The glycerin needs to be carefully drained from the bottom.
• Centrifuging the mixture can speed up separation.

Purification (Washing & Drying)

• Warm water (35–40°C) is required to wash away any impurities.
• Acid (e.g., acetic acid, citric acid) is required for neutralization.
• A drying chamber or heater to remove any water.
• In the first wash, add an equal volume of warm water (1 liter per liter of biodiesel).
• Mix gently for 5–10 minutes, let settle for 30 minutes, and drain the water layer from the bottom.
• Second & third washes are required if the wash water is not clear.
• A few drops of acetic acid can neutralize the residual catalyst if required.
• The washed biodiesel should be heated to 100–120°C for 30 minutes to remove water.

Final Yield

• Biodiesel yield is ~90–95% of initial oil weight, which equates to ~900–950 ml biodiesel per 1 liter of oil.
• Glycerin yield is ~10–15%, which equates to ~100–150 ml per 1 liter of oil.