Learn to Make Your Own Biodiesel - Part 1

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Making Biodiesel - Heating the Vegetable Oil

vegetable oil heated to 100 degrees fahrenheit
photo © Adrian Gable

We brew our homemade biodiesel from waste vegetable oil in heavy-duty plastic 5-gallon buckets. We do this to keep batches small to allow for easy handling and transporting the finished product.

The first step is to heat the oil to approximately 100 degrees F. We accomplish this by putting the oil in a steel pot and warming it on a camp stove. That does allow us to do this in the basement, keeping all processes concentrated in one area. Be sure not to overheat the oil. If it gets too hot, it will cause secondary ingredients to adversely react.

In warmer weather, we skip the stove heating and set buckets of oil in the sun. In just a few hours, they're ready to process. While the oil is heating, we move on to the next steps.

For our normal batch, we use 15 liters of vegetable oil.

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Safe Handling & Dispensing of the Methanol

drum of M100 racing methanol
photo © Adrian Gable

Methanol is one of the three main ingredients used to make biodiesel. We like to buy our methanol in 54-gallon drums from a local race shop. It tends to be most economical that way. Make sure that the barrel pump used for transferring methanol is rated for alcohol. As you can see, they are usually made of a yellow nylon material. It's non-reactive and non-conductive.

For our normal batch, we use 2.6 liters of methanol.

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Safe Handling of the Lye

container of household lye
photo © Adrian Gable

Lye, also known as Sodium Hydroxide (NaOH), and caustic soda, is the third ingredient used to make biodiesel. Look for it at plumbing supply houses or from chemical suppliers on the internet.

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Measuring the Lye

Weighing lye on a balance for BD making
photo © Adrian Gable

The most expensive piece of equipment we use for making homemade biodiesel is a good quality balance. You can also use a high-quality electronic scale, but it's important that it is precise. Accurately measuring the appropriate amount of lye is critical to a successful biodiesel reaction. Having a measurement that is off as few as a couple of grams can make the difference between success and failure.

For our normal batch, we use 53 grams of lye.

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Mixing Sodium Methoxide

Mixing sodium methoxide from lye and methanol
photo © Adrian Gable

Sodium methoxide is the true ingredient that reacts with vegetable oil to make biodiesel (methyl esters). In this step, the methanol and lye that were measured and dispensed in the previous steps are brought together to make sodium methoxide.

Sodium methoxide is an extremely caustic base. The vapors that the mixing process emits, as well as the liquid itself, are extremely toxic. Be absolutely certain to wear heavy-duty synthetic rubber gloves, eye protection, and an approved respirator.

As you can see, the mixing tools are simple. We use a coffee can and a speed-bore bit with the tip ground off and chucked in a hand drill. There really is no need to spend a lot of money on equipment--much of it can be homemade. It takes approximately 5 minutes of spinning the blade in the liquid in the coffee can to dissolve the lye crystals.

Note: The liquid will get warm as the reaction occurs.

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Adding Heated Oil to the Bucket

biodiesel - adding oil to bucket
photo © Adrian Gable

After the oil is heated, pour it into the mixing bucket. The bucket must be completely dry and free of any residue. The residue of any substance left behind can upset the delicate reaction and ruin the batch of biodiesel.

We like to use recycled 5-gallon spackle buckets or restaurant supply buckets. If you're going to use a bucket made out of other materials, you'll need to test it first to make sure it can withstand the biodiesel reaction.

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Adding Sodium Methoxide to the Oil in the Mixing Bucket

Adding sodium methoxide to the oil in the biodiesel mixing bucket
photo © Adrian Gable

At this point, we generally like to add half of the sodium methoxide to the oil in the mixing bucket and then give the remaining sodium methoxide another one or two minutes of mixing. This extra mixing will fully dissolve any remaining lye crystals.

Note: Any undissolved lye crystals can upset the reaction. Add the last remaining bit to the oil in the mixing bucket. At this point, you'll begin to see a very small reaction as the sodium methoxide makes contact with the oil. It bubbles and swirls!

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Before We Start to Mix the Biodiesel

Before We Start to Mix the Biodiesel
photo © Adrian Gable

Finally, all of the sodium methoxide has been added to the oil and it is a rich chestnut color. (That's about to change.)

The beater that you see in this picture was salvaged from a discarded industrial mixer. Cost: our time to dig through a pile of scrap steel. You could just as easily buy an inexpensive drill operated paint mixer that would do the same thing.

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The First Minute of the Mixing Process

Agitation of veg oil and sodium methoxide
photo © Adrian Gable

We took this picture to show you what the first minute of the reaction looks like. As you can see, it's a muddy, cloudy-looking mixture. As the beater spins for the first minute or two, you may actually hear a load on the motor and it will slow a bit. What's happening is that the mixture is thickening slightly just before the main chemical reaction starts to take place, as the glycerin begins to separate out from the vegetable oil. At that point you may hear the motor pick up speed as the oil thins out and the separation continues.

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Continuing the Mixing Process

biodiesel mixing apparatus
photo © Adrian Gable

As you might guess from this picture, the entire mixing apparatus is homemade. Everything was made from materials that we had available in our shop, except for the drill. We splurged and spent $17 on a regular 110-volt hand drill at Harbor Freight (my real tools are too good to use for this process). The drill will get greasy and slopped up, so we caution you against using your good tools as well.

We keep a lid on top of the mixing bucket to help contain splashes. To feed the mixing shaft to the drill, we bored a 1-inch diameter hole and fed the bit through. In spite of how simple this apparatus looks, it works amazingly well. Set the speed of the drill somewhere around 1,000 RPMs and let it run for 30 minutes continuously. This ensures a complete and thorough reaction. You don't have to babysit this part of the process. We always set a kitchen timer and take care of other tasks while the mixer is running.

After the timer beeps, turn off the drill and remove the bucket from the mixer. Set the bucket aside, place a lid on it, and let it stand overnight. It will take at least 12 hours for the glycerin to settle out.

Proceed to Part 2 to See Us Finish the Process