The Process of Making Bio-Diesel
By Sean Armstrong, Edmund Koontz and Celeste Peltier
With special thanks to Andy Cooper and Panama Bartholomy (Spring 2000)

Index

Stage 1: Initial Filtering
Stage 2: Making the Catalyst
Stage 3: Mixing it All Up
Stage 4: Settling Down
Stage 5: Storage & Final Filtering
Conclusion
Bibliography

The biodiesel refinery at CCAT consists of five stages. The University of Idaho Department of Agriculture in 1991 defined making biodiesel, or transesterification, as the "process of using an alcohol (e.g., methanol or ethanol) in the presence of a catalyst, such as sodium hydroxide or potassium hydroxide, to chemically break the molecule of the raw renewable oil into methyl or ethyl esters of the renewable oil with glycerol as a byproduct (Making Biodiesel)." The process of making biodiesel will be described in the next three paragraphs.

Stage 1: Initial Filtering

Used vegetable oil from two different restaurants

Simple but effective screens

Once the used vegetable oil has been obtained it is filtered through a wire screen to remove all of the food particles. At CCAT we make 30 gallon batches in donated oil barrels (Thanks Spectrum!), and the filtered oil is then poured into a fifty gallon barrel. We begin heating the oil in the barrel to a temperature between 100-120 degrees F using a propane burner.

Stage 2: Making the catalyst

While the oil is heating we perform a titration using a 10 ml sample of the homogenous solution to determine the amount of lye (the catalyst) needed. Methanol in a standard 1/5 proportion to the amount of oil is combined with the determined amount of lye (sodium hydroxide) in a micro reactor to make sodium methoxide.

Here is the recipe and materials list for determining the amount of lye needed. This was taken directly from the folks at www.namecraft.com/dancing-rabbit/biodiesel:

You will need

Titration Process to determine how much Lye to use

Free fatty acids will increase with the amount of time vegetable oil has been heated-- oil which has been used for cooking will require more of the reactive agents-- lye and methanol-- than fresh oil. The presence of too many free fatty acids will retard or stop the reaction which produces biodiesel, so it is necessary to detect the exact amount of LYE (Sodium Hydroxide-- or NaOH) needed to neutralize the acids. Adding too much or too little NaOH will just make excessive amounts of By-product (soap).

An example formula used with one particular batch of WVO-wasted vegetable oil. 1 ml of oil was titrated with a 1g NaOH/1000 ml H2O solution. It required 6.0 ml to raise the pH level to 8 = .006g so 6.0g/1000ml to neutralize the free fatty acids plus 3.5 g NaOH as catalyst = 9.5 g per 1000ml oil or 9.5g/915g oil=103% by wt

The determined amount of lye is added to the methanol in a separate plastic jug with a hole in the lid to allow the agitator to be powered by an attached drill. The drill attachment allows the sodium methoxide to be stirred without exposure to this extremely toxic chemical. If methanol is not available ethanol can be used instead, but more is required.

!!! Remember, the sodium methoxide you have just made is toxic and can do damage to your nervous system if it touches your skin. Take every precautionary step possible to contain and isolate the sodium methoxide and to prevent your unprotected skin from coming in contact with it !!!

The metal agitator fits into an electric drill head

The agitator CCAT uses to stir the methanol and lye mixture.

The agitator stirs the sodium methoxide in an isolated container for safety.

Stage 3: Mixing it all up

The sodium methoxide solution is then added to the heated oil. The propane burner is still required continue heating the oil for the next hour as the solution is stirred. At CCAT we use a small electric outboard motor to stir the solution. We found this to be the cheapest effective mixer for making 30 gallon batches of biodiesel.