Easy Intro to Homemade Bio-fuels – Part One: Biodiesel


A plain language explanation of Biodiesel and Straight Vegetable Oil technology. No auto repair experience required.

This intro is going to focus on diesel engines, and oil based fuels. Ethanol and other homemade fuels can be used in gasoline engines, but I have less experience/knowledge of that, and will save it for another essay.

This is not meant to be a step-by-step tutorial, but more of an introduction to and explanation of the process. There are many tutorials online. Here’s a good one (How to Make Biodiesel at Home). There’s a great online forum as well. (Biodiesel and SVO forums)

Avoid the site Journey to Forever, which is easy to stumble across when first looking for info. It is out-of-date and has quite a few errors. Eventually I’ll post my own tutorial on this site.

So the first thing to know then is that there are two different kinds of automobile engines, diesel and gasoline. Biodiesel and straight vegetable oil can only be used in diesel engines.

Note: In case you weren’t quite sure, Straight Vegetable Oil is just that. Pure vegetable oil. In all but a few cases, homebrew biofuel is made using waste vegetable oil. When filtered of particles and water, WVO is still quite usuable as a fuel. (Except when of lower quality from overuse and contamination.)


When Rudolph Diesel first introduced his new engine at the 1900 World Fair in Paris, it ran on peanut oil. It wasn’t until Diesel’s mysterious death 13 years later that a method was discovered to make diesel fuel from petroluem by-product (the left-overs from the gasoline production process.)

Difference between Diesel and Gasoline engines

Both kinds of engines are similiar in that they use small explosions to move pistons up and down in a cylinder. In a gasoline engine, fuel is mixed with air, compressed by pistons and ignited by sparks from spark plugs. In a diesel engine, the air is compressed first, and then the fuel is injected. The air heats up when it’s compressed, thus igniting the fuel.

This difference allows for the use of oils in a diesel engine which are much less flamable than petroleum.

Diesel engines today

Diesel engines still operate on the same basic principle as they did a hundred years ago, the main difference being that they have been engineered to handle a less thicker oil than peanut or veggie oil. (When speaking of oils, the word viscousity is used to describe the thickness of oil. Petroluem diesel is less viscous than vegetable oil, and vegetable oil has a higher viscousity than petro-diesel.)

Therefore, the process of using vegetable oil in diesel engine involves reducing the viscousity of the oil. Once this has happened, the resulting fluid is for all purposes diesel fuel.

Two processes for reducing oil viscousity

The two basic processes that you would use at home to reduce the viscousity of vegetable oil are mechanical and chemical.

The mechanical process involves heating the oil to approx. 80 degrees celsius. Straight vegetable oil conversions involve installing components into the fuel-delivery system of a diesel vehicle to heat the oil, so that it is injected into the engine at the right viscousity.

The chemical process involves using chemicals (lye and methanol) to reduce the viscousity of the oil. This process is called transesterification, and is basically the process of stripping the oil of glycerine. Once this glycerine has been removed from the oil, it is the proper viscousity for modern diesel engines, and becomes bio-diesel.

Making Biodiesel

We’ll start with the chemical process, for no particular reason. Whether you use bio-diesel or Straight Vegetable Oil (SVO) is a personal choice. I’ll get into the pros and cons of each method later. However, if you do use SVO, you still need to use petro-diesel or bio-diesel to start and warm up the engine. The excess heat that the engine produces when it is running is a main source or heat for the SVO process.

As I said earlier, making bio-diesel is a chemical process of thinning the oil, by using methanol and lye to strip the glycerine from it. The glycerine from this process (though brown and smelling of french fries) can be used to make soap. (perhaps just a shop soap).

Essentially, the process of transesterification happens when a catalyst (in most cases lye) is introduced to the oil in the presence of an alcohol. The catalyst causes the glyercine to seperate from the oil, and is replaced by the alcohol.

So simply put, lye is added to methanol, creating something called methoxide. This methoxide is then added to warm oil (80 degrees C) and mixed for about an hour. Then the oil is left to cool for about 8 hours, during which time the glyerine will settle to the bottom of whatever you are mixing the oil and methoxide in, and the oil left on top of the glycerine is biodiesel.

The bidiesel is then washed (a process of gently mixing water into the fuel) and letting it settle out. (Settling for about 12 hours and repeated twice.)

Equipment for making biodiesel

People have been known to make biodiesel in buckets and drums using blender like objects like electric boat motors or drill mounted paint stirrers. I’ve even made it while travelling in 5 gallon jugs by agitating the jugs by hand. These are unsafe and inefficient methods however, and much better equipment is easily built using inexpensive parts.

A very popular design for homebrew biodiesel making involves using a hot water heater, a water pump and a series of pipes and valves. Aside from the cost of the water heater, the parts involved should come out to less than $300 for a simple unit.
The design for this unit is open source, meaning no one owns the patent to it, and plans, innovations and modifications are freely shared by a large and passionate online community. The most popular forum can be found here.

In the simplest terms, a biodiesel processor is a giant, heated blender than heats the oil and blends the two liquids together.

In the past few years, innovations have occured in the homebrew community than has seen the creation of new designs (example) which have eliminated the need for the water washing step (which uses about three times as much water as oil) and allow for a greater volume of methanol to be reclaimed. In the simpler designs, the methanol was left to evaporate into the air.

Using Biodiesel in your vehicle

The alcohol content of biodiesel makes it slightly corrosive to natural rubber. In newer vehicles this is less of a problem, but in older vehicles, certain hoses and gaskets will need to be replaced. This is fairly simple and will cost $200-300. A synthetic materical called fluoroelastomer is generally used.

Also, I am just starting to read about ULSD (Ultra Low Sulfer Diesel) Emission engines and the issues they have running biodiesel. These engines were came into production in some vehicles in 2007. There are fixes and work-arounds for these issues, but it is important to do your research (the above mentioned forums are a great source of info) specific to your vehicle.

Aside from the biofuel forums, you can also find infomation on online forums specific to you vehicle. It seems every make and model has an online forum, and the diesel models tend to have a few people posting on them who have experience with biodiesel. Also, these forums are a great place to get info on locating and reparing different parts of your vehicle.

I had no auto repair experience before learning how to make biodiesel and convert vehicles to run on SVO. I taught myself everything I know by reading online, asking questions on the forums (if a search of the forums didn’t reveal that my question had already been asked, and it usually had) and visting people locally who had experience and were willing to share. You may also want to hire someone like myself (hint, hint) to either help you as a consultant in the process or do a lot of the work for you. It’s important however to have knowledge of how the process works, so that you can avoid creating problems for yourself.

Next time I’ll talk a bit about using Straight Vegetable Oil, and what you need to do to your vehicle to do so,
If you have any questions, don’t hestitate to ask, especially if it can be helpful in making this intro even more easy to understand.

(Next – Part Two: Straight Vegetable Oil)

Also: Alternative Ingredients and Methods for Making Biodiesel

2 responses »

  1. Pingback: Alternative Ingredients and Methods for Making Biodiesel « The Dreamer Propulsion Project

  2. Pingback: WVO For Home Heating « The Dreamer Propulsion Project

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