Beverly writes: Hi, I really appreciated your site that speaks to failed biodiesel. Since you stated that you have dealt with practically every known kind of failure, I wondered if you could give insight to my situation. I've been making biodiesel 2 1/2 years without trouble--or at least, without any batches that could not be salvaged. But the last 3 batches have failed, and I am stumped.
I have checked the water content in the oil: it is very low. The oil titrates low, per usual (it is from a hospital cafeteria, and it titrates less than 2 each time). I use KOH, which has been kept in an airtight container and closed between uses. The pump on my Appleseed works well, the processor heats fine. We even had the methanol tested by the dealer (they sent it to a lab), and it checks out just fine. So I can find nothing that would result in 3 failed batches of light mushroom soup. Before making the last batch, I did a 1-liter test batch (with extra methanol to push the reaction, just to be sure) and it split fine (except with a higher glycerine amount), so I felt that I had gotten over whatever the problem was.
You made a couple of interesting remarks in your article which I would like more clarification on, if possible. You mentioned scrubbing your processor, something I have never done, although I have tipped my processor to drain it as much as possible. Is scrubbing the processor necessary? Is mushroom soup a sign of too much KOH? I don't know how to read this result. I have tried reprocessing with more KOH (because I wondered if I used too little methoxide) but the results show no separation, just cloudy brown oil. And sometimes this separates into white gunk toward the bottom. Is that soap? :^/ I did not know that too much lye could cause soap in the process--I thought it would just be a supreme annoyance in the washing (emulsion overload). If too much KOH is the culprit, does it take very much extra to cause this problem? Also, do you think the KOH could be bad? It isn't clumping, such as I observed once when some humidity got into a bag (which we threw out). I did not think it was the problem.
I would appreciate your input. I have never had this particular problem before and I was feeling very confident about how well I had things under control (esp after 2 1/2 years!). Thanks in advance for whatever light you can shed on this problem. It surely is an annoyance. If we cannot resolve it we will have to quit making biodiesel--which I had hoped to continue doing.
Sincerely,
Beverly
Hi Beverly, We like to answer questions in a systematic fashion, so we’re just going to filter down through your questions and comments one-by-one.
B—Hi, I really appreciated your site that speaks to failed biodiesel. Since you stated that you have dealt with practically every known kind of failure, I wondered if you could give insight to my situation. I've been making biodiesel 2 1/2 years without trouble--or at least, without any batches that could not be salvaged. But the last 3 batches have failed, and I am stumped.
C&S—Thank you for the kind words regarding our website. We congratulate you for making biodiesel (BD) for the past 2½ years without having any unsalvageable batches. That is an impressive testament to your skills and thoroughness. Making BD is as much of an art as it is a science.
B—I have checked the water content in the oil: it is very low. The oil titrates low, per usual (it is from a hospital cafeteria, and it titrates less than 2 each time). I use KOH, which has been kept in an airtight container and closed between uses. The pump on my Appleseed works well, the processor heats fine. We even had the methanol tested by the dealer (they sent it to a lab), and it checks out just fine. So I can find nothing that would result in 3 failed batches of light mushroom soup. Before making the last batch, I did a 1-liter test batch (with extra methanol to push the reaction, just to be sure) and it split fine (except with a higher glycerine amount), so I felt that I had gotten over whatever the problem was.
C&S—Usually a soupy reaction means either too much KOH (lye), too little methanol, or a bad ingredient. Since you had your methanol supply tested, and it passed, and you keep your lye sealed tight, we can disregard those as culprits with reasonable certainty. Further, since you checked the oil for water, and that passed, we’ll dismiss moisture problems. Our guess at this point would be a change in the fundamental characteristics of the waste oil (see the paragraph below), or an unreliable titration test. Titration is a good guide, but we think test batches are more accurate. They are essentially a proof-is-in-the-pudding assurance. In other words, if the ingredients “convert to BD” in a 1-liter test batch, then a full-blown real batch at identical ratios should convert as well. You say that you added “extra methanol” to push the reaction in the test batch and it was successful. This makes us suspicious of the initial titration. The addition of extra methanol may have “watered down” what was a too-much-lye recipe indicated by a compromised titration. Does this make sense? Our learned-the-hard-way-rule: No matter what the titration “says,” use it only as a guide and go with the test batch numbers.
One final thought we’d offer is to check with the cafeteria staff and see if they’ve changed practices in the kitchen. Over the years, we’ve had an otherwise reliable source of oil change-the-game and all of a sudden the oil is no longer usable. Sometimes to save money, a kitchen manager will start using preservation treatments (special chemicals) to prolong the cooking life of the oil and reduce change-out times. Often these chemicals can upset (and even prevent) a BD reaction. If this is the case, you may have to find another supply. The fact that you did get one good test batch would seem to eliminate bad oil as a culprit, but is it possible that you’ve mixed known good older oil with potentially bad newer oil?