How to make biodiesel

A few facts on biodiesel

Biodiesel is biodegradable and non-toxic. 100% biodiesel is as biodegradable as sugar and less toxic than table salt. It biodegrades up-to four times faster than petroleum diesel fuel with up-to 98% biodegradation in three weeks. However, contrary to a popular misconception, it stores indefinitely in completely full, cool, dark containers. Compared to crappy fossil fuel diesel, biodiesel has the following emissions characteristics:

100% reduction of net carbon dioxide
100% reduction of sulphur dioxide
40-60% reduction of soot emissions
10-50% reduction of carbon monoxide
a reduction of all polycyclic aromatic hydrocarbons (PAHs) and specifically the reduction of the following carcinogenic PAHs:
phenanthren by 97%
benxofloroanthen by 56%
benz-a-pyrene by 71%
aldehydes and aromatic compounds by 13%
5-10% reduction of nitrous oxide depending on age and tuning of vehicle.

For every one ton of fossil fuel burnt, 3 tons of CO2 is released into the atmosphere, biodiesel only releases the CO2 that it has taken in while the plants it is made from were growing, therefore there is no negative impact on the carbon cycle.

How to build a single tank biodiesel processor

Firstly though, we have to say that our biodiesel expert is not longer involved in SchNEWS so we are not able to offer any advice or further information on the subject further than what's here. There are websites listed at the bottom of the page which contain loads more info. Please don't email us asking questions about biodiesel as we won't be able to help.

Equipment required

45 gallon drum.
1/2 or 3/4 Hp electric motor.
Two pulleys which produce 250 rpm and a max of 750 rpm at mixer blade.
A belt for the above.
12 inch rolled steel rod.
Two steel shelf brackets (for the blade).
1 1/2 inch (38mm) brass ball valve.
A hinge and a spring to act as a belt tensioned.
2000-watt electric water heater element.
A water heater thermostat.
1 1/2 diameter piece of steel pipe * 3-5 inches long with male threads on one end.
Assorted tat: angle iron, wood, screws etc.


Cut a large opening (about half the top) in the top of the steel drum.
Drill 11/2-inch hole in the bottom of the drum.
Weld the 1 1/2-diameter pipe in the hole at the bottom of the drum.
Attach the 1 1/2-inch brass ball valve to the pipe. This is the drain valve.
Drill a hole in the side of the drum at the bottom, same size as the heater element.
Fit the heater element making sure it is not touching the side of the drum.
Wire up the heater element.

Chemical mixer

Attach one pulley to the rolled steel rod.
Attach the other pulley to the spindle of the electric motor.
Weld the propeller to the other end of the rolled steel rod (shelf brackets).
Attach the rod, pulley and propeller assembly to one side of the hinge.
Weld a piece of angle iron across the top of the drum.
Weld the unattached side of the hinge to the angle iron so the propeller and rod assembly sits in the middle of the drum. The hinge should swing the propeller and rod back and forth.
Mount the electric motor on the side of the drum.
Fit the belt to the pulleys and tighten by wedging a block of wood into the hinge.
You also need to fashion a simple wooden measuring stick with 10 litre increments.

Other bits and bobs

A hydrometer is a good piece of kit to have to measure the specific gravity of the biodiesel. The specific gravity of biodiesel should be between 0.860 and 0.900, usually 0.880. The specific gravity of vegetable oil is 0.920 therefore the specific gravity of biodiesel should be lower than the vegetable oil used to make the biodiesel.

How to make biodiesel
Every time you make a new batch of biodiesel using old vegetable oil you have to find out the amount of reactants required to get the correct reaction, this process is know as titration. In addition to the above equipment you will also need the following equipment:

Petri dish

20 ml beaker

1500 ml beaker

500 ml beaker

Isopropyl alcohol

A graduated eye dropper

Litmus paper

Blender with a glass bowl.


Used cooking oil

Sodium Hydroxide


Step 1 Titration: to determine the quantity of catalyst required

Measure 1 gram of Sodium Hydroxide onto a petri dish
Measure 1 Lt. of distilled water into a 1500 ml beaker.
Pour the 1 gram of Sodium Hydroxide into the 1 Lt. of distilled water
Label ‘do not drink Sodium Hydroxide’
Measure 10 ml of isopropyl alcohol into a 20ml beaker
Dissolve 1ml of used vegetable oil into the isopropyl alcohol.
Label oil/alcohol.
Use the graduated eye dropper to drop 1 millilitre of Sodium Hydroxide /water solution into the oil/alcohol solution
After 1 millilitre of Sodium Hydroxide /water solution is added check the pH
Repeat steps 8&9 until the oil/alcohol reaches a pH of between 8&9. The pH increase will usually occur suddenly. Usually no more than 3 millilitres of Sodium Hydroxide /water solution will need to be added.
Use the following equation: · the number of millilitres of the Sodium Hydroxide/water solution dropped into the oil/alcohol mixture = x · (x+3.5)=N
· N= the number of grams of Sodium Hydroxide required to neutralise and react 1 Litre of used vegetable oil.

· N will be between 4.5-6.5, but it can be higher if the oil has been used for a long time.

Step 2. Measure the reactants

Measure the reactants in separate containers

1 Litre of filtered used oil into a 1500ml beaker

200 ml of methanol into a 500 ml beaker

N grams of Sodium Hydroxide onto a petri dish

Step 3. Dissolve the Sodium Hydroxide into the Methanol

The third step is to combine the methanol with the Sodium Hydroxide to create sodium methoxide, an extremely strong base. Once the Sodium Hydroxide has been dissolved in the methanol, the sodium methoxide must be mixed with the vegetable oil straight away.

· Carefully pour the methanol into the blender, any spills must be cleaned immediately with a water and vinegar solution.

· Carefully pour the Sodium Hydroxide into the blender

· Replace the lid of the blender and blend on the lowest setting for 30 seconds, until the Sodium Hydroxide has dissolved. Sodium methoxide has been produced and caution must be exercised

Step 4. Mix the reactants

· Remove the lid of the blender keeping your face well away from the top of the blender

· carefully pour the vegetable oil into the blender

· Place the lid on the blender and blend on a medium/high setting for 15 minutes. If the bowl or the blender motor get over hot switch off the blender and leave until cooled down sufficiently to continue again.

Step 5. Allow the glycerine to settle

Settling takes about 8 hours but since 75% of the separation occurs within the first hour after the reaction immediate separation will be visible. Within 8 hours the glycerine will have fallen to the bottom leaving a layer on top, this is methyl esters, or more commonly referred to as biodiesel

Step 6. Separation

After blending the contents can either be transferred into a 1500ml container with a stopcock or left in the blender for at least 8 hours.

Step 7. Clean up

Store the leftover used vegetable oil in a dry cool place

Clean all the equipment so it is ready to use again

Expose the glycerine to air and sunlight for 1 week and then use as soap.

Pour the biodiesel into your fuel tank and laugh like fuck!

So there you have it, fuel from vegetable oil. Of course this is only one method of making biodiesel, there are many recipes for making biodiesel just take a look through the web sites at the end of this article. Don’t be fooled into thinking that biodiesel is anything but a serious contender in the alternative fuels market, throughout the world there are commercial processors being built to supply a rapidly emerging market. The UK government however, has chosen to ignore biodiesel, this is their mistake and something we can capitalise on. Let’s start making biodiesel and get production down to the local small scale level with co-operatives and individuals supplying all our needs while taking power away from the mega-corporations.

For more information on biodiesel check out rather than emailing us, we're no experts, unfortunately. Alternatively the first book on the following website (LILI: how to make biodiesel by Dan Carter & Jon Halle) has been recommended to us: The Low Impact Living Initiative website also has other information and equipment for biodiesel and other related topics.

Useful related posts:

Do It Yourself Guide in Making Biodiesel

Biodiesel: The Definitive Guide

Other Useful web sites:


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