Biofuels mailing list member Ken Provost, who has much experience making ethyl esters, sent us the following tips&tricks sheet.
Ethanol-based Biodiesel
1. Get plenty of experience making biodiesel with methanol before you try it with ethanol. Get comfortable titrating your oil for FFAs (free fatty acids); you’ll need to do that when you use ethanol.
2. Try to find a source of KOH (potassium hydroxide) to use instead of lye with ethanol. Lye (NaOH, sodium hydroxide) will work, but it dissolves VERY slowly in ethanol. You'll need to use more of either one -- 7g per liter of clean oil with NaOH, 10g per liter of clean oil with KOH. More as required per your titration level.
3. Your ethanol will have to be EXTREMELY dry. 199-proof or higher. "Absolute" ethanol. Any more than one half of one percent water can kill the reaction. Denaturants like methanol, isopropyl alcohol, MIBK, etc., are fine. But no water. Ethanol that dry is difficult to find cheap, especially in the US. If you want to try to make it yourself, you'll need molecular sieve, quicklime, or something else to do a "chemical" drying. Distillation alone can't get the water under 5% -- still way too much. (See below -- Anhydrous ethanol)
4. If you're interested in ethanol for environmental reasons, be careful. Even if you find anhydrous ethanol, it may come from fossil fuel. The denatured alcohols used by painters, or in other industrial applications, may be anhydrous but still derived from petroleum. In fact, since fermentation uses water, it's cheaper to make 200-proof starting with petroleum. The only way to know is to call the original manufacturer of the formula. Ask if the ethanol is "synthetic" or "fermentation". One type of denatured anhydrous ethanol that is almost always fermented is "fuel-grade", which is 199-proof denatured with gasoline. It's what they add to gasoline to make gasohol.
5. Your oil will also have to be EXTREMELY dry. Heat the oil to 120 deg C (248 deg F) and hold it there until you can turn off the flame and see the bubbling stop almost immediately. You might want to throw in some clumping cat litter (bentonite clay) and/or silica gel to scarf up any remaining water, let it settle half a day, and take the oil off the top. Sometimes that's still not dry enough. Remember -- any more than 0.5% water can kill the reaction.
6. Your oil will have to be fairly low in FFAs. You'll want to do a titration on every batch to make sure. Anything over 2 ml titration (using 0.1% NaOH solution) can cause failure of the glycerine to separate -- under 1 ml is a good idea. Most waste oil is too high, and either needs to be refined with NaOH first, or cut with clean oil to neutralize FFAs.
7. You need to use more ethanol to get full conversion. Somewhere between 275 and 300 ml per liter of oil is about right for most oils. Coconut oil will need more, maybe 350 ml. Theoretical is about 180 ml per liter, and the rest is excess to drive the reaction all the way.
8. Even when you do all the above, getting the glycerine to separate is a matter of good luck and fervent prayer. Sometimes separation occurs just like a methanol batch. Other times you won't start seeing a glycerine layer for 3 or 4 hours, or maybe overnight. Then again, sometimes it NEVER separates. Until you get separation, you haven't made biodiesel. I've heard of folks who don't wait for separation -- they just pour the whole mess right into the tank, or do some kind of water wash and think it's good biodiesel. It might burn, but it's not biodiesel. It must separate.
9. If it doesn't separate, you can sometimes force it by adding some methoxide mix. You can also make it more likely to separate by including some methanol with the ethanol right from the start. For example, you could try using an initial mix of 5 to 7 parts ethanol and 1 part methanol. Give it a few hours to separate. If it doesn't, add some straight methoxide to the kettle, using enough methanol to bring the alcohols ratio down to 3:1 eth:meth, and containing another 2g of KOH per liter of oil. That usually initiates separation within an hour. Fresh, refined edible oil might even work the first time with straight ethanol. If you use a mixture of ethanol and methanol, you can get away with 275 ml of initial mix per liter of oil.
10. If you're not scared off yet, Good Luck!
-- Ken Provost
