Editorial Feature

Make Your Own Biodiesel

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The consistent and constant rise in fuel prices across the globe are a clear indication of the depletion of the world's oil resources. As a result biofuel, and biodiesel in particular as it is the most available, is now regarded as an affordable and easy to use alternative to oil.

What is Biodiesel?

Biodiesel is created by chemically altering organic oil, such as vegetable oils, animal fats, and recycled cooking oil, through a transesterification process. The biodiesel is produced through a refining process which mixes the vegetable oil or animal fat with alcohol in order to remove the by-product glycerine. It can also be used in diesel engines with very few modifications. Biodiesel is biodegradable, nontoxic, and essentially free of sulfur and aromatics.

The Environmental Benefits of Biodiesel

Biodiesel emissions have between 45 and 90% lower toxic emissions compared to conventional diesel fuel. Its handling and storage are safer than regular diesel fuel. Biodiesel is usually mixed with petroleum diesel in order to ensure cool-weather performance, reduce cost and improve engine compatibility. B20, a mix of 80% petroleum diesel and 20% biodiesel, is the most common mixture used.

Animal fat or vegetable oil and grease dumped in a landfill can also be used to fuel vehicles, thereby reducing waste. Biodiesel from waste cooking oil is said to be the most eco-friendly liquid fuel as the chief ingredient is the waste product. However, waste vegetable oil also has more non-oil contaminants compared to virgin oil.

Biodiesel has a closed carbon cycle, which means the CO2 released into the atmosphere during burning of biodiesel is recycled by growing plants which are in turn processed again into fuel.

Making Biodiesel From Vegetable Oil

The production of biodiesel involves the use of methanol and sodium hydroxide or lye, which are dangerous in their pure form. As a result, rubber gloves and safety goggles are highly recommended while handling these substances.

Vegetable oil is a triglyceride consisting of a chain of one glycerin molecule and three vegetable molecules. During the process of biodiesel manufacturing, the glycerin is replaced with methanol in the process of transesterification.

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Waste or new vegetable oil can be used for biodiesel production. However, using virgin resources is the less eco-friendly way to produce biodiesel. Waste vegetable oil can be easily obtained from many restaurants as they have to pay for removing and processing their used cooking oil.

Firstly the oil is heated to approximately 100°F. Titration helps determine how much catalyst you must add by indicating the acidity of your oil. Accurately measuring the appropriate amount of lye and methanol is critical to a successful biodiesel reaction. The measured methanol and lye are brought together to form sodium methoxide. The vapors released during the mixing process are highly toxic, and hence it is necessary to wear heavy duty synthetic rubber gloves, eye protection and an approved respirator.

When the oil is heated, it is poured into a separate beaker and added with small quantity of sodium methoxide for mixing. Then the remaining sodium methoxide is added to the mixture and mixed for 1 or 2 min to dissolve any remaining lye crystals. Any undissolved lye crystals can interfere with the chemical reaction that takes place. By the end of the mixing process, the mixture tends to bubble and swirl due to the contact of sodium methoxide with the oil. After blending, the mixture is left alone to settle for at least 8 h during which the two layers, glycerin on the bottom and biodiesel on top are formed.

The Economic Benefits of Biodiesel

As an optimal fuel for the diesel engine, biodiesel offers superior lubricity and helps reduce engine wear, even as an additive. It also reduces the dependence on foreign oil and increases agricultural revenue while also creating jobs.  

Whilst state fuel tax applies to vehicles which run on homemade biodiesel, the first 400 gallons of home-made biodiesel are exempt from federal taxation. It is often said that biodiesel production at home could cost less than 20p per litre.

References and Further Reading

Alexander Chilton

Written by

Alexander Chilton

Alexander has a BSc in Physics from the University of Sheffield. After graduating, he spent two years working in Sheffield for a large UK-based law firm, before relocating back to the North West and joining the editorial team at AZoNetwork. Alexander is particularly interested in the history and philosophy of science, as well as science communication. Outside of work, Alexander can often be found at gigs, record shopping or watching Crewe Alexandra trying to avoid relegation to League Two.


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