Guest Post By Adaptive Curmudgeon: January 2010
I intended to describe the entire process, start to finish, of making biodiesel in it’s full glory. But after a few bouts with the keyboard I realized I couldn’t include everything without boring everyone to death with minor details. So this article starts with the explicit understanding that I’ll paint a picture with broad strokes. It is my assumption (and insistence) that anyone intending to make biodiesel should be wise enough to check further before setting to work. For anyone new to biodiesel I so recommend reading my introductory post: Seven Basic Facts About Biodiesel for some background.
My second assumption is that anyone making their own biodiesel is possessed of a heaping helping of common sense. I could blather on about safety and so on but I’m neither a lawyer nor enamored with them so I’ll put a warning right here. You’re dealing with fuel. It’s flammable and merits appropriate precautions! If you didn’t figure that out on your own, you should try another hobby; perhaps Skee Ball? Also you’ll be using chemicals. Smart folks in lab coats have recommendations about the safe handling of chemicals. Do what they say. Enough of the caveats, on to the story.
To start with you need oil. Biodiesel can be made from various materials but generally the source (feedstock) is vegetable oil scrounged (with permission!) from a restaurant’s fryer. It comes in degrees of desirability but you can generally deal with most of it. You’ll filter out the “floaties” (leftover bits of French fries) and remove water using the all important fact that oil floats on water. Once your oil is crudely filtered and “dewatered” you’ve made significant progress.
Then comes the part where you wish you had paid attention in chemistry class. (I didn’t.) You draw a small sample of oil and test its pH. That data is plugged into a formula, chart, or on-line worksheet to determine a “recipe” for your specific oil sample. Remember when I said oil used comes in varying degrees of desirability? This is where it shows up. “Good” oil uses less input components and is less sensitive to a screw up. “Bad” oil requires a defter touch.
Despite covering this earlier I’m going to add another warning. Most of the processes involved relate to harmless stuff like water and vegetable oil. The next step deals with more powerful materials; methanol and lye. For the brief time you’re handling these materials be on the ball. Plan ahead, wear appropriate protective gear, and pay attention. Methanol (which is a lot like gasoline with extra kick) is mixed with lye (which is a caustic substance used as a drain cleaner and in making soap). Didn’t I tell you it was a good time to be paying attention? The two are mixed to produce methoxide, which is both caustic and flammable.
The methoxide you’ve made gets mixed into the oil. Once you’ve mixed all of that witches brew into the oil you can breathe a sigh of relief. (If you planned carefully you kept it around only a few minutes you didn’t have to handle it much.) Almost immediately a chemical reaction starts which changes the oil from translucent golden to opaque dark chocolate. Congratulations, you’ve done something. If you measured right you’ve done good. If you inadequately “dewatered” the oil or mixed the wrong amount or strength of methoxide you’ve made a gloppy mess.
It takes time for the next step but it’s my favorite because I can claim to be “working” on it while lounging on the couch. Raw biodiesel will gradually separate out and rise to the surface. Byproducts will sink to the bottom. The biodiesel at this point is probably sub-par (in my humble opinion) but many people use it like this. I take additional steps to assure superb quality fuel. It’s your choice.
The next step (which is theoretically optional) is to make absolutely positively sure that the golden fluid you’re looking at is really biodiesel and it is as pure as possible. I start by testing it to make sure there isn’t excess unreacted vegetable oil lurking in my fine product. The test is simple and painless and if you did your recipe right the result is nearly always a “pass”. What about excess methanol or other undesirable components? The secret to this is, ironically, water. Water, which would have caused hassles in earlier steps, is now your friend. Methanol and other impurities will happily bond to water. Biodiesel doesn’t like water and floats on top of it. Water added to the top of the biodiesel will sink and gather the bad stuff on the way down. Alternatively you can put the biodiesel on top of water and run air bubbles through water and oil together. I do both. This seemingly crude arrangement gently “washes” my biodiesel until it’s crystal clear. It’s a thing of beauty.
By “washing” it in this manner you’ve just added water to your fuel (which seems like a terrible sin). So your last step is to let the water settle out. With a bit of elapsed time the water sinks yet again and you can draw your biodiesel from the top. I go the extra mile and run it once through a spin on filter. I’m not sure it needs it but it seems wise.
Of course I’ve glossed over a lot of details but that’s just what they are; details. The overall process is disarmingly simple. There are only four ingredients; oil, methanol, lye, and (as a filtering mechanism) water. Careful attention to detail (and that final water wash process) will reliably make a clean, clear, and excellent biodiesel.
In my next article I’ll discuss some of the logistics involved. At first I expected chemistry to be the matter of most import. Instead I discovered that mundane concerns ranging from buckets and barrels to pipes and pumps really carried more weight. No reason to keep the hints and tips I’ve learned secret. You may find some of my discoveries useful.
Adaptive Curmudgeon, January 2010
Some other useful beginner biodiesel resources:
- Anyone Can Make Biodiesel from Home (article)
- Willie Nelson on Biodesel (article)
- Biodiesel Basics and Beyond (book)
- Do-It-Yourselfer Guides to Biodiesel (books)
More About Biodisel: