How do you measure how much WVO goes in and how much Bio comes out? In most cases this is done by volume.
The density of wvo varies depending on the original veg oil used, the degree of oxidation (FFA), but usually between about 0.905 and 0.925.
The denisty of Bio varies also depending on the original veg oil etc. but again between about 0.86 and 0.90.
The density of pure glycerol is about 1.260.
The density of methanol is about 0.800
All these are at about 20C and obviously change with change in temperature (increase when colder, decrease when warmer).
Using the no titration method tends to use less methanol.
If you were to use 100L of dry WVO and 15L of methanol along with 600g of NaOH and assuming the oil titrated at 0.
On average 12.5L of methanol would actually be used.
Assuming a perfect world, with perfect conversion and no by products:
100L of oil weighing 86Kg would convert to Bio weighing 86Kg (glycerol MW about 92 and methanol about 32 so 96 equivalent when converted).
If we assume the MW of Olein is 375 and that WVO is near enough olien, then that 375 will become 379 once converted to bio so about 1% more by weight.
If we assume that the oil is 0.9 density and the bio is 0.86 density, then there will be between 4 and 5% more Bio by volume than there was WVO.
The 12.5L of methanol would weigh 10Kg and produce 96/92 times as much glycerol so under 8L of glycerol, there would also be 600g of NaOH in the glycerol.
There would also be 2.5L of methanol disolved in the glycerl and bio.
In practice using caustic to make the catalyst solution produces water which catalyses the formation of soap. Of course if there are impurities in the WVO these could skew the results in any direction. The presence of FFA for example would lead to the formation of Soap by neutralisation. The soap and water will predominately be in the glycerol, however the presence of the methanol will allow soap to remain in the Bio. Using ASM (Anhydrous Sodium Methylate) rather than caustic will not cause water to be formed and therefore shoul create little to no soap other than that of neutralising FFA.
How you "wash" the bio will also have a large effect on how much actual bio you recover. Water washing with soap present will usually result in the loss of some bio. Bubble washing to remove the methanol and precipitate out the soap shoud preserve more bio, if that is followed by water washing there should be much less loss of bio.
Other variable such as temperature will also have an influcence on how much bio you recover.
If you have glycerol washed you WVO beforehand to reduce FFA and water content then wether you measure before washing of after could make a large differnce.
Lots of variables to consider but the simplest thing is that 100L of WVO could give you about 105L of Bio.
Posted under the influence of a couple of glasses of processed grape juice
