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Bio-Diesel production by products, what do you do with them? Answered

I have seen some folks hawking their books for DIY Home Made Bio-Diesel.  Ok, it can be done but what do you do with the byproducts, i.e. the initial sluge produced when titrating the primary oil with lye, then washing the resulting oil with water to titrate out the soap?  It seems to me a lot of work and mess to deal with.


Perhaps I don't have the authority to say this, but as an aspiring biodiesel retailer I think my word is trustworthy. As far as I've read, biodiesel doesn't have any negative effects on performance. Not to mention is burns cleaner. The glycerin isn't an issue depending on where you live; you can just mix it in with the diesel in hot-start engines (read: during warm weather), but seperate it out during the cold months, as it can begin to gel or solidify and will clog your engine. Not fun to repair. I reccomend researching the matter further at your local coomunity college or university, and as far as the internet goes, search it on makezine.

Hi All - I just did some more research on bio diesel.  It is dubious at best I think, if you make algae bio, you have the algae cake to deal with, then with the bio diesel production you have the glycrine slug to deal with.  On one hand you can produce a life time and more supply of soap!  Some scientists have discovered using e.coli bacteria in an anaerobic fermentation process to make ethanol, frees up corn and soybean production for food. Then the car and truck manufacturers point out that bio diesel literally blows past the piston rings and builds up in the crank case, more problems.  So at this point for myself,  I have some to the conclusion unfortunately, continue using petroleum diesel until the bio diesel gets things worked out and don't even use a bio mix use straight petro diesel! 

You shouldn't use lye. Enzyme catalysis or potassiummethoxide. As steve' says, it's mostly glycerine, a bit basic but you could add vinegar and flush it.


Neutralise any remaining alkali.


Lemonie - Ok, it is coming back to me from High School Chemistry Class, by adding the vinegar you are neutralizing and the remainder is a salt and water correct?  The glycerine I am not sure about. What bacteria consumes glycerine?  I live in a rural area and don't want the DNR pounding on my door.

Yes. Bacteria will "eat" pretty much anything, glycerine is pretty harmless, as is acetate. You wouldn't want to dump a lot of organic material into a natural water flow, but domestic sewage should be OK (as long as you're not operating as a business)


Enzyme catalysis ? I didn't know there was an enzyme method.  

What's wrong with the sodium methoxide method ? 


People have used esterases, but 'hydroxide is more common. Potassium hydroxide is more soluble in methanol than sodium, and without checking, so is the alkoxide (I believe) - it works better.
(I don't need to advise you on Googling "biodiesel transesterification process enzyme")


Indeed that was my VERY search term (without the word "process")when you mentioned the existence of the stuff. Not that I have a yen to make any, mind.

As enzymes go lipases can be pretty cheap, if the source says porcine or bovine you don't have to think that hard to realise where they're coming from. Still KOH is cheap too.


Bovine? I might retract that, but PPL (Porcine Pancreatic Lipase I have used)


Its a long time since I read up on this, but isn't the main byproduct glycerine, mixed with the catalyst ? Since the methoxide is a catalyst, I've wondered how it can be recovered too.

Glycerine will break down rapidly in the environment I think - bacteria will eat it willingly.