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June 2006

Pull out your lab goggles, we’re making biodiesel

There is a growing segment of Americans who are becoming increasingly frustrated with rising fuel prices. As a result, many are turning to alternative sources of fuel. One of the most popular is biodiesel. The number of people who home-brew their own fuel is rising, and recipes for biodiesel may be found on any number of websites. So grab your lab goggles and chemistry kits, we’re going to show you how to make biodiesel for fun and profit.

Actually, there is very little chemistry in the process of making biodiesel. However, before we begin, you will need to gather several things. The main and most important ingredient is waste vegetable oil (WVO). This may be obtained from many restaurants in your area. Call them and ask for their old oil. Most will be happy to let you pick it up from them for free.

The next ingredient in the mixture is methanol (CH3OH). It is important that it be 99% pure. Methanol can be found at chemical supply stores, or at the local racetrack. Methanol is toxic, and may cause blindness or even death, so use caution when you handle it. It is absorbed through the skin, so wear protective gloves and eyewear whenever you are handling it. Also be careful to avoid breathing in fumes if you work in an enclosed area.

The final ingredient for the mixture itself is sodium hydroxide (NaOH, also known as caustic soda or lye). This must be kept as dry as possible in an airtight container. All instruments used to measure and stir lye should also be kept as dry as possible

You will need a very accurate scale to measure the amount of lye to add to within a hundredth of a gram. This is also a dangerous chemical that you need to be cautious handling. Wear gloves and eye protection to reduce the chance of accidents.

You cannot just throw all of the above ingredients together and run a truck on the result. There is another step in the process called titration that needs to be performed on the WVO to determine the quantity of lye you’ll need to add.

Titration is the most crucial step, and it should be taken slowly and all measurements should be as accurate as possible. For this you will need 99% pure isopropyl alcohol, distilled water, phenolphthalein solution (not more than a year old, and kept away from strong sunlight). Phenol or phenol red from pool supply stores may not be the same substance. Be sure to get your phenolphthalein from a reputable chemical store.

The final step is called washing, and for this you will need water and vinegar.

For the entire process, you will need several largish containers (size depends on how large a batch you plan on making) to hold and mix ingredients in, and they will get messy. Containers used for biodiesel should never be used for any other purpose afterwards.

Step 1- Filtering
You will need to filter the WVO to remove any food particles in it. If it is too thick, you may have to heat it up to run it through a filter. 95°F (35°C) should work. Once it is warm, pour the WVO through a funnel lined with a double layer of cheese cloth.

Step 2- Removing water
WVO will sometimes contain water content. This is undesirable since any water left in the oil will form soap when reacted with lye. Heat the WVO to about 212°F (100°C). Allow the water to boil off, but be careful that steam pockets do not splash hot oil out of the heating vessel. When the boiling slows, raise the temperature to 265°F (130°C) for 10 minutes. Then remove the heat and allow the WVO to cool.

Step 3- Titration
Make a solution of one gram of lye to one liter of distilled water. Make sure the lye is completely dissolved. In a separate small container, mix 10 milliliters of isopropyl alcohol with 1 milliliter of your WVO.

Add two drops of phenolphthalein to the alcohol/oil mix. Using a graduated eye dropper, or some other instrument marked in tenths of milliliters, vigorously stir in several tenths of a milliliter of your lye/water solution to your oil/alcohol mix at a time. Keep careful track of how many milliliters of solution you have to add until the mixture turns pink for 10 seconds.

Step 4- The Calculation
Take the number of milliliters you added in the titration step and multiply by the number of liters of WVO you will be processing. Also, for each liter of WVO, you will need to add an additional 3.5 grams of lye. So for example, if you used 2.4 milliliters in titration and you have 150 liters of WVO, then 2.4 x 150 = 360 grams plus 3.5 x 150 = 525 grams. So 360 + 525 = 885 total grams of lye to be added.

Step 5- Preparing the Sodium Methoxide
The amount of methanol you’ll need is about 20% of the volume of WVO you are processing. So for our example of 150 liters of WVO, you would need 20% of 150 liters, or 30 liters of methanol.

Mix the methanol with the amount of lye that you calculated in a glass, enamel, or stainless steel container. Tin, aluminum or zinc containers will all react with the lye, producing undesirable results. The methanol will react with the lye to form sodium methoxide.

Sodium methoxide is a dangerous chemical. If it gets on your skin, it will burn you without you feeling it, so if it gets on you, use large amounts of water to flush the skin immediately. Try to have a hose running wherever you are working with this and other dangerous chemicals. Always follow standard safety procedure by wearing goggles, gloves and apron while handling the chemicals.

Step 6- Heating and Mixing
Pre-heat the WVO to 120-130?°F (48-54°C). A paint stirrer on an electric drill will serve as a mixer. Add the sodium methoxide to the WVO while stirring. You should stir the mixture for about an hour. If this is too long to hold a drill, you may want to assemble a rig to hold it in place over your mixing vat/bucket. Adjust the speed of the drill so that there is no splashing. You want a vortex to just appear on the surface.

Step 7- Separation
Allow the newly mixed solution to settle for a minimum of eight hours. The biodiesel will float on top while a denser product called glycerine will have congealed on the bottom. Suspended in the biodiesel will also be soapy residues. Neither the gylcerine nor the soap is wanted in the finished product, so washing is required.

Step 8- Washing
Siphon the biodiesel out of the container into one without the glycerine mess at the bottom. The glycerine has many uses, and you may find people locally that would like to take it from you. Look for a local materials exchange program. Otherwise it may be composted after letting it vent for three weeks to allow methanol to evaporate off.

Now that the glycerine has been removed, you will need to get the soapy residues out of the biodiesel. It is a good idea to add a little vinegar to the solution to remove any left over lye and bring the pH level closer to seven (neutral).

Next you’ll need to get a container to use for the washing. Try to find a container that is translucent. Then you’ll need to install two valves, one as near to the bottom as possible, and one that is just high enough to sit above the level of the water you will be using to wash your biodiesel.

Fill the container with water to a little below your upper valve. Then put your biodiesel in the rest of the container. Gently stir the water and oil together. Be careful to not agitate the soaps with hard stirring. After a thorough mixing, allow the solution to sit for 12-24 hours. The denser soapy water will settle to the bottom allowing you to decant off the cleaned biodiesel through your upper valve. Once the fuel has been decanted out, you can drain and dispose of the water.

Repeat this process two or three times to clean as much soap as possible from the fuel. For these additional cleanings, it is not necessary to add vinegar.

Step 9- Drying
After a third washing, you will want to remove any leftover water in the biodiesel. Slowly reheat the oil, and the water and impurities will sink to the bottom. The finished biodiesel should have a pH of seven as confirmed by litmus paper or a digital pH tester.

Congratulations! You’re on your way to fuel self-sufficiency.

Bear in mind that this is a rough guide to the fine art of biodiesel creation. Additional research is strongly encouraged on the subject if you truly wish to run machinery on the results.

An online resource for aspiring biodiesel home-brewers can be visited at

Please remember to be safe when experimenting and follow all recommended safety tips. American Recycler intends this to be informative, not a set of comprehensive instructions, and as such, will not accept liability for any damages to persons or machinery resulting from information contained in this article.

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