Our Green Streets Blog

Since my last post on the merits of biodiesel, I’ve been able to gather more information and I wanted to pass it on to you.  What continues to intrigue me about home brewing biodiesel is that it is emblematic of the type of lifestyle changes we all need to take on in the 21st century.  Taking waste frier oil and converting it, at home into a cleaner burning, less toxic and more biodegradable fuel is something akin to modern day alchemy.

First, a disclaimer:  I am not a home brewer, just an interested by-stander.  I cannot, and do not warrant any of the  designs exhibited for performance nor safety.  There are a number of excellent books available on the subject for anyone looking to tackle their own setup.  As with all things, safety first!

I’ve taken a lot of instruction from user Jerry (Airthug) at biodieselpictures.com, sponsored by the excellent source of biodiesel brewing equipment, Utah Biodiesel Supply.  

The Basic Process

1. Heat the oil to remove any water content. (95-120 degrees F)
2. Pre-filter waste vegetable oil to ensure that it is free of debris and food particles.
3. Perform a “titration.”  – this step seems complex at first, but it’s really not too bad and only takes about half a minute.  The purpose of titration is to determine the amount of FFA (Free Fatty Acid) in the waste oil.  This is necessary because lye (sodium hydroxide) is required to make the oil and the methanol react, but FFAs will “use up” some of the lye as the lye and FFA combine to make soap.  Titration, then, is used to determine the amount of extra lye that needs to be added so that there’s enough left over for the Transesterfication reaction to take place.  Exhaustive instructions/methods for titration can be found here.
4. Measure the proper amount of catalyst (lye) and combine with the methanol, heat and stir.
5. Heat oil, mix in lye and methanol circulate for about an hour, then pump to wash tank. 
6. Once the reacted mix has settled for 12-48 hours, drain off glycerine.
7. Wash bio by pumping in warm (90-120F) water through an aerator and draining excess wash water from the bottom of the tank.  The oil should also be warm (85-95F) so that everything flows freely.  Pause to bubble (with a submerged aerator) for about an hour half way through the wash.  Wash until water drawn off is no longer cloudy.
8. Perform a PH test on your wash water, and bring back to a neutral PH of 7 by adding calculated amount of vinegar prior to disposing in sewer.  Don’t water plants with this water as it’s still dirty.  Once PH neutral, a water treatment plant can easily deal with the wash water.
9. Dry the bio by heating it to 150 degrees F and pumping via recirculating pump through aerator head to maximize surface area.
10. Once rested, draw off a sample and test for water content.  500 Parts Per Million is the most water allowed in finished biodiesel by ASTM spec.

It should be mentioned that there are many approaches to cleaning the biodiesel, and the water wash outlined above is not the only way to go.  Other methods exist that can clean impurities without the need for any water.

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