I get a lot of questions about soap and toiletries. I answer anywhere between 120 – 200 emails, every day. My staff answer that or double that daily. The most frequently asked question I’ve gotten this year has got to be about making soap from biodiesel glycerin. Glycerin is a natural byproduct from the biodiesel refining process. In the photo above, the glycerin is on the right. The biodisel is on the left. I personally would not ever use this glycerin as an ingredient in soap but there are a lot of people that would like to, purity concerns be damned. I am posting my thoughts on this interesting subject for all to see, in the hopes that it educates and possibly stems the endless tide of “I know this is a really strange question, but I make biodiesel and I was wondering ….” emails.
I do not personally recommend making soap with the byproduct glycerin from biodiesel manufacturing as I don’t think it’s entirely clean and pure and has some extra things like methanol in it. However, we do have a local customer in Bellingham, WA that does make a soft, smushy, gray looking bar of solid, slightly lathering soap with their byproduct bio-diesel. They have shared a bar with me and while it is soap, it is very soft and fairly poor in terms of lather. This is probably due to the fact that it is 100% glycerin which is not entirely saponifiable by lye.
If you really want to use the byproduct glycerin, I would recommend a more modified, traditional recipe such as:
16 oz. Coconut Oil
16 oz. Palm Oil
32 oz. Olive Oil
16 oz. Liquid Glycerin
Lye 9.4 oz.
Water 16 ounces
Please not that you must do a certain amount of safety precautions to make lye and I strongly recommend researching how to make cold process soap prior to attempting to make it. My favorite books The SoapMaker’s Companion by Susan Miller Cavitch to learn about soapmaking or The Natural Soap Book, also by Susan Miller Cavitch. My favorite DVD on the subject (by moi) would also be a good starting point for learning how to make CP soap.
The recipe above will be soft but will lather decently and last much longer than 100% glycerin soap.
Also, you might think about other things like fire-starters with your by-product liquid glycerin.
david crump says
I am making bio diesel liquid soap and works great.
I use the glycerin from the bio diesel reaction.
I am getting free, partially hydrogenated soybean oil and partially hydrogenated cottonseed oil that was used to make donuts.
It is solid at room temp and have purchased several pounds of NaOH.
My question is how much NaOH and water should I mix to make a good bar soap???
I am obviously not using it to make any bio diesel so I will be converting it all to soap.
How should I titrate this oil to determine the correct amount of NaOH and how much water.
You can use a lye calculator: https://www.brambleberry.com/Pages/Lye-Calculator.aspx to determine how to much lye you need for how much oil you have. Please please please please learn about safety with making lye based soap (goggles, gloves, no kids, no pets, etc…) before you start. SoapQueen.TV has four free “cold process” (lye) soapmaking episodes that might be of help to you. =)
FYI…In the photo the biodiesel is on the right and the glycerin is on the left.
I would love to try the soap! Thanks … (popping over to your site now)
Using the black crown soap guide we have been able to make a terrific quality bar and liquid soap that both lather quite well. Please visit our website at http://www.washtyme.com and we’ll send you some complimentary bars to try and update your readers.
http://www.blackcrownsoap.com/ is a new site that has PDF files on how to make soap from the raw biodiesel glycerine and also how to turn your sopa making into a small business.