Worst biodiesel batch yet!

[Ivan]

My usual WVO titrates a 0.7ml (amount of NaOH 0.1M required to neutralise it).

As the weather is starting to warm, I thought I'd try including some of that treacly stuff from the bottom of the waste containers. It titrated at 8ml, and produced almost 40litres of glycerine (the excess was FFAs) instead of the usual 20litres (from 100litres)

This weekend, I tried using a bit more of the crappy stuff, but ended up with a titration of 18mls 

I used the 5% prewash technique, which is supposed to aid separation and reduce soap. Just as well, I suppose, as I could see a 'high-tide' line of caked soap on the side of the reactor, which needed to be scraped off by hand (around 1litre of soap!). The 5% prewash adds some volume, but I was disappointed to find glycerine layer (+5% prewash) accounted for 60litres of the total volume (120litres).

Emulsion-city in the first wash, and difficult separation in the 2nd wash. Just put in the third wash, before giving up for the evening. Oh, and some solidified glyerine stopping the pumps running, despite my best efforts.

How much usable biodiesel do you think will result? I'm guessing around 40-50litres. 

[Ian]

Ivan - Something does not sound right here. (Note that I have never made bio diesel but I am a Chemist by training...)

My understanding is that esterification of a triglyceride will produce around 10% glycerine (glycerol). It just is not possible to make 40 - 50% glycerine; there must be something else in that layer. My guess is that you have  a mix of glycerine, water and "complexes" (starch, sugars, waxes, gums) and maybe some high melting point animal fats that were not esterified for some reason.

We have all been taught that water and oils do not mix but I am frequently amazed at how easy it is to create a mayonnaise type emulsion with very little energy input just by adding water to WVO and shaking it a bit. Over a (long) period of time the emulsion usually breaks down but I have never yet managed to later collect anywhere near the same amount of oil as was originally added to the emulsion. I think this goes to show just how much emulsifiers and gums come out of the food and into the oil when it is being cooked.

Whilst I do not make bio diesel, I still use WVO and, being a skinflint (father was a Yorkshireman!), I try to use as much of the collected WVO as possible. In my case, I use a sock filter to separate the liquid oil from the solid, waxy part of the mayonnaise mix. I guess I get about 15 - 20 Kg of solid wax / animal fat retained in the sock filter for every 100 litres of WVO and maybe up to 2 Kg of water. The liquid stuff passing through the sock filter is bright and clear and stays this way even when refigerated down to about 2 - 5 degrees C. Most of my WVO is soya or rape based.

Regards,
Ian

[Twenty4Seven]

Ivan

Was the WVO dry prior to reacting?

Nick

[Ivan]

Yes, it was dry.

You normally get 20%. This is a mixture of glycerine, catalyst and methanol. Poor quality titrations have lots of free fatty acids ('FFA'). These do not convert in the standard single-stage reaction. Thus they end up in the glycerine layer. Not sure what a titration of 18 equates to, but clearly a LOT of FFAs. When the glycerine layer settles, you can clearly see the FFAs as a white/off white layer in the glycerine.

[frotter]

I found a similar thing when i used to bother to make bioEvil.... lardy oil would make way more glycerol and was a complete pain... I often ended up burning the solid stuff on the bonfire rather than mess about with it.....
Could do with it now!