How to Recycle Used Cooking Oil into Biodiesel Fuel

How to Recycle Used Cooking Oil into Biodiesel Fuel

How to Recycle Used Cooking Oil into Biodiesel Fuel


Recycling used cooking oil into biodiesel fuel is a great way to reduce waste and make your own renewable fuel. Biodiesel is an alternative fuel made from vegetable oils, animal fats, or recycled restaurant greases. It can be used in any diesel engine without modifications. Converting used cooking oil into biodiesel is a relatively simple process that can be done at home with minimal equipment and effort. In this article, I’ll walk you through the entire process step-by-step.

Gathering Used Cooking Oil

The first step is collecting a sufficient amount of used cooking oil. Here are some tips:

  • Restaurants – Ask restaurants if they have any waste vegetable oil they are looking to get rid of. Most restaurants deep fry foods and have lots of used oil. Make sure the oil has not been mixed with animal fat.

  • Household oil – Save oil used for cooking at home. Strain out any food debris using a fine mesh strainer or cheesecloth.

  • Avoid – Oil that contains animal fats or has been mixed with gasoline or kerosene.

  • Quantity – For your first batch, start with 2-5 liters of used oil. You can scale up as you get comfortable with the process.

  • Storage – Keep the oil in a cool, dark place until you are ready to start the conversion process. Dark bottles work great for storage.

Making Biodiesel – Supplies Needed

Biodiesel production requires some basic equipment and chemicals. Here is what you’ll need:

  • Methanol – The main chemical used in the reaction process. You’ll need 500 ml methanol per 1 liter of cooking oil.

  • Lye – Also called sodium hydroxide (NaOH). Converts the oil to biodiesel. Use 3.5 grams NaOH per liter of oil.

  • Reactor vessel – A container to mix the oil, methanol, and lye in. A 5 liter plastic bucket with a lid works well.

  • Electric mixer – Needed to properly blend the oil and chemicals together. A handheld immersion blender is perfect.

  • Funnel & cheesecloth – For straining the finished biodiesel from the glycerin byproduct.

  • Glass jars or bottles – To store the finished biodiesel fuel in. Use 1 liter bottles with tight sealing lids.

Making Biodiesel – Step-by-Step Process

Here is the full step-by-step process for converting used cooking oil into usable biodiesel fuel:

Step 1 – Mix the Methanol and Lye

  • Measure out the correct amounts of methanol and lye as outlined above based on how much used oil you have.
  • Pour the methanol into the reactor vessel first.
  • Slowly add the lye to the methanol while stirring gently. Never add water or touch lye with bare hands!
  • Allow the lye/methanol mixture to cool down before proceeding.

Step 2 – Add Oil and Mix

  • Once cooled, slowly pour in the used cooking oil.
  • Use the immersion blender to thoroughly mix the oil and methanol/lye solution together for at least 5 minutes.
  • The mixture will become cloudy and yellowish as the chemical reaction takes place.

Step 3 – Let it React

  • Allow the oil/methanol/lye mixture to react for 24 hours.
  • Cover the bucket, but do not seal it completely. Gases need to escape.
  • The mixture will settle into two layers – biodiesel fuel on top and glycerin waste on the bottom.

Step 4 – Wash and Dry

  • After 24 hours, drain off the top biodiesel layer using a funnel and cheesecloth.
  • Put the biodiesel in a bottle and add warm water. Shake vigorously and let sit for 30 minutes.
  • Drain off the water using the funnel and repeat the washing process 2-3 more times until the water runs clear.
  • Do a final rinse with warm salt water to pull out any remaining impurities.
  • Allow the biodiesel to dry completely before use.

And that’s it – you now have usable biodiesel created from recycled cooking oil! Always take safety precautions when handling chemicals.

Using Homemade Biodiesel

Biodiesel can be used as a direct replacement for petroleum diesel in any conventional diesel engine. Here are some usage tips:

  • Start with a blend – Try a 20% biodiesel/80% conventional diesel blend in your engine first to check compatibility.

  • Cold weather – Biodiesel gels at higher temperatures than petrodiesel. Use higher ratios of conventional diesel in cold weather.

  • Storage – Store biodiesel in a cool, dark place in sealed containers. It will degrade faster than petrodiesel if left exposed.

  • Filters – Change fuel filters after first using biodiesel as it can dislodge debris in fuel lines and tanks initially.

  • Usage – Best used within 6 months for highest quality if storing homemade biodiesel.

So be sure to follow all safety precautions, and you can enjoy the satisfaction of using renewable biodiesel you made yourself from recycled materials!


Converting used cooking oil into biodiesel fuel provides an excellent way to reuse waste oils while creating your own renewable fuel. This saves money, reduces pollution, and helps power your vehicles with a cleaner burning diesel alternative. The full conversion process only requires some readily available materials and basic equipment to complete safely at home. Now that you know the essential steps involved, you can start recycling oil and making biodiesel fuel yourself! Just be sure to take all necessary safety precautions when handling chemicals like methanol and lye.