The Heart of Biodiesel Production

Transesterification is the key chemical process used to produce biodiesel from organic oils and fats. It involves the conversion of triglycerides (found in oils and fats) into esters, typically methyl esters, which form biodiesel. Let’s delve into this pivotal process in detail:

Basics of Transesterification

In simple terms, transesterification is the reaction between a triglyceride (oil/fat) and an alcohol (usually methanol) to produce biodiesel (methyl ester) and glycerol.

Chemical Reaction

Triglyceride + 3 Methanol → 3 Methyl Ester (Biodiesel) + Glycerol

Note: This reaction is usually facilitated by a catalyst, commonly sodium hydroxide (NaOH) or potassium hydroxide (KOH).

Steps in Transesterification

1. Mixing of Reactants

The oil/fat is mixed with an alcohol, typically methanol. This mixture is often heated to ensure complete mixing and to maintain the reaction temperature.

2. Catalyst Introduction

A catalyst (alkaline or acidic) is introduced to speed up the reaction. The choice of catalyst depends on the feedstock’s acidity. Sodium or potassium hydroxide is used for low acidity oils, while acidic catalysts are used for oils with higher acidity.

3. Reaction Phase

The mixture is kept at a specified temperature (usually around 60°C or 140°F) for a certain duration, allowing the transesterification to take place.

4. Settling or Separation

After the reaction, the mixture is allowed to settle. Due to differences in density, biodiesel rises to the top, and glycerol settles at the bottom. They can then be separated.

Equipment Used in Transesterification:

  • Reactors: Vessels where the actual chemical reaction takes place.
  • Agitators or Mixers: Ensure thorough mixing of the reactants.
  • Heat Exchangers: Maintain or adjust the temperature during the reaction.
  • Settling Tanks or Centrifuges: Used to separate biodiesel from glycerol.

Considerations for Efficient Transesterification

  • Molar Ratio: The ratio of alcohol to oil/fat is crucial. Typically, a molar ratio of 6:1 (methanol to oil) is employed to ensure complete conversion.
  • Purity of Reactants: The presence of water or impurities can hamper the reaction and result in soap formation.
  • Catalyst Amount: Proper measurement of the catalyst is essential for reaction efficiency and cost-effectiveness.
  • Reaction Time & Temperature: These parameters should be optimized for the specific feedstock and equipment used.


Transesterification is the central process in biodiesel production, transforming organic oils into renewable fuel. Ensuring precise conditions and purity of reactants will yield high-quality biodiesel suitable for engines.