According to the Journey to Forever biodiesel making guide, potash (KOH or potassium hydroxide) is the easiest and most effective catalyst. As a catalyst, potash mixes with methanol and vegetable oil to break down some of the acidity and free fatty acid (FFA) in pure or waste vegetable oil. Another popular catalyst is caustic soda (NaOH or sodium hydroxide). Substituting potash for caustic soda is advisable, but never mix the two in the same batch.
Instructions
1. Buy your potash in the highest possible concentration. Check the label and get no less than 85 percent purity. The higher the percentage, the higher the cost, so 85 percent is acceptable for providing adequate results.
2. Begin with a test batch. Find a recipe for the size and purity that you seek and follow it precisely. You do not need a biodiesel processor to make a test batch, but you can make a mini processor at home with spare plastic bottles, tubing, funnels and an iron pot.
3. Mix the potash with methanol. Calculate 1.4 times more potash than sodium hydroxide if you are substituting potash for sodium hyrdoxide. Make sure the potash dissolves completely.
4. Blend your chosen amount of vegetable oil into the potash and methanol mixture in your biodiesel generator. Follow the same process as with any other catalyst. The byproduct of this part of the process is soap and glycerin. Potash produces a much smoother and cleaner byproduct, making the entire process gentler.
5. Store the catalyst in a dry place where it is well protected from the air. As a hygroscopic chemical, potassium hydroxide reacts with carbon monoxide and absorbs oxygen from the air. Seal any remaining catalyst and methanol in airtight containers.
Tags: caustic soda, potassium hydroxide, sodium hydroxide, test batch, with methanol