Washing Tanks

Washing Tanks

Washing is a pivotal step in biodiesel production, ensuring the removal of contaminants, residues, and any by-products. Washing tanks play a central role in this phase. Let’s delve deeper into their functions, designs, and significance.


After the transesterification process, biodiesel might contain traces of methanol, catalysts, soap, and other contaminants. The primary function of washing tanks is to:

  • Remove Residual Catalysts: Sodium or potassium hydroxide used as catalysts need to be eliminated.
  • Eliminate Methanol Residue: Any remaining methanol from the transesterification process is washed out.
  • Purge Soaps: The reaction between catalysts and free fatty acids (FFA) can create soaps. These need to be removed to ensure fuel quality.

Types of Washing

There are mainly two types of washing methods in biodiesel production:

  • Water Washing: This is the traditional method where water is sprayed or mixed with biodiesel. The contaminants are water-soluble and hence settle at the bottom, allowing for separation. This method, while effective, can lead to water contamination and demands efficient drying methods afterward.
  • Dry Washing: Instead of water, dry washing uses solid resins or absorbent materials (like magnesol) to remove contaminants. As no water is introduced, the drying step is avoided, making the process faster and sometimes more efficient.

Design and Features

A typical washing tank is designed to cater to the specific washing method:

  • Inlet and Outlet Ports: For the introduction of biodiesel and discharge of washed biodiesel.
  • Spray Nozzles: Used in water washing to ensure even distribution of water.
  • Agitators: To ensure thorough mixing. Essential in both water and dry washing.
  • Settling Area: Allows contaminants or water to settle at the bottom.
  • Sampling Ports: To periodically check the quality and ascertain the removal of contaminants.
  • Drainage Ports: To drain out water or contaminants settled at the bottom.

Significance in Biodiesel Production

  • Fuel Quality: Washing ensures that biodiesel meets the desired quality standards, enhancing its performance and reducing engine complications.
  • Environmental Compliance: Clean biodiesel burns more efficiently, reducing emissions and environmental impact.
  • Economic Value: High-quality biodiesel can fetch better market prices and is more accepted by consumers.


Washing tanks are indispensable in the biodiesel production process, ensuring that the end product is of high quality and free from contaminants. Whether using water or dry washing, the objective remains the same: producing clean, efficient, and environmentally friendly biodiesel.