We often receive letters from readers regarding biodiesel, hybrids and other alt fuel questions. We recently received one from Tom, a guy who has been experimenting with making his own biodiesel, and thought his dilemma and solution would be a good one to share with y'all:
Scott and Christine,
A friend and I have been splitting the oil I've picked up from two restaurants. We have noticed that in some of the 5 gallon buckets there is a "growth" of fat on the insides of the buckets but no clumps in the middle. In other buckets of oil from the same two restaurants there is no "growth" and when heated and filtered through a coffee filter, the filters look the same and the oil looks good. If I let the filtered oil sit for several weeks (I am slow about being able to process it due to my work - truck driver) some of the oil will have the "growth" but to a lot lesser degree. My friend plans to use SVO and is concerned that the fat growth is actually hydrogenation and that supposedly is not good for SVO users. By the way, since I have not read anything about using hydrogenated oil in making BD I assume it makes no difference. Is there a way to test the oil for hydrogenation? Is hydrogenated oil difficult to process for BD or do I not need to be concerned?
Thanks, Tom
We've experienced many of the very issues that Tom has raised, and we were able to share our insight in our reply:
Hey Tom,
It sounds like your oil might possibly be liquefied shortening. Some restaurants use that in lieu of pure vegetable oil because it's less expensive, but it doesn't go completely solid (like shortening) when cool--it just thickens a bit and kinda gets a white creamy tinge along the edges.
It's also possible that it is pure veg oil, but it has some water in it (maybe the buckets got rain in 'em while the they were awaiting pickup). This seems the more plausible scenario, since after you heat and filter it, there is less "growth" in the buckets. What may be happening here, is while you heat it for filtering, you're boiling off some (but not all) of the moisture suspended in the oil. Then when it cools again, you'll get some of the growth again, but not as much. Try heating it for a longer time (maybe an extra 10 - 15 minutes) at a slightly higher temperature (about 140 degrees F) and see if that fixes things up. If it's clean after that, you're good to go, but if it still gets some "growth, you're better off passing on this stuff and finding another source.
As far as hydrogenated oil goes, I would stay away from it if you can get good pure veg oil from other sources. I have successfully made BD with it, but the titrations are trickier and it can fail unexpectedly. And definitely don't use it in an SVO setup--takes too long and too much heat to liquefy enough to flow through the pump and injectors. This goes double if you live in a cold climate.
Good luck and hope my answers help, Scott
Looks like Tom "stuck to his guns" and worked his problems out:
Well, Scott, yesterday was a good day, dry and sunny with temp 65. I had filtered some of my oil through coffee filters after straining it through screen wire and a "T" shirt. It looked good so I did a titration and came up with 1.5. I used my first recipe and added it to 4 giving me 5.5. I mixed the lye with 200 ml of methanol (in an HDPE 2 bottle), dissolved it thoroughly (venting twice). I heated the oil to 145 for 15 to 20 minutes to check for water. Seeing no steam or bubbles, I wiped a pan with oil on a paper towel and placed it on a hot plate until it smoked. I then put a tablespoon of the oil into the pan and watched it spread rapidly over the pan but no popping or cracking. I immediately dropped one drop of water into the oil and watched the water sizzle, crackle, bounce, etc. Now I was sure the oil was water free. I allowed the liter of oil to cool to 110 F. I continued by adding the liter of hot oil to the methanol. After shaking the mixture gently for 15 minutes (again in an HDPE 2 bottle) and venting the fumes twice, I poured it into a V/8 Juice bottle and set it aside to settle for 30 minutes. Later I noticed a slight separation and left it overnight. Today I checked on the batch and "Voila" I had about 1/2 in of black gunk on the bottom of the bottle and 5-3/8 inches of tea colored biodiesel.
As I have mentioned I have been getting oil from two restaurants. One says they are not using hydrogenated oil. The other one doesn't know. I have made 5 batches from some of the oil and given some away. Not paying attention to detail caused a real bad batch. I either was not measuring something correctly or the oil was coming from the same source and was hydrogenated. The first 3 batches were great, then came a failure. Everything stayed cloudy with no separation. I tossed it and did another from what I assumed was the same oil. This time It had about 2 inches of almost clear fluid on top and the rest was a block of spongy gunk that would not go through the neck of the V/8 bottle. I tossed it and then came along the success of yesterday. By the way, the two failures titrated out at 3.0 and 3.2 respectively.
I tell you all of this to say that the good batches, I believe, came from one restaurant and were pure oil (not hydrogenated) according to the grill cook. The two failures, I believe, came from the restaurant that doesn't know if their oil is hydrogenated or not. I suspect it is! Thanks for telling me about hard titrations and sometimes sudden failure with hydrogenated oil. Tom
And if you're curious to check out what's involved in making your own biodiesel, be sure to take a look at our making biodiesel photo tutorial - and get the low-down on making your own fuel from veggie oil.