I wonder about the color consistency of your biodiesel brewing and if a correlation exists between color and with say...soap content...maybe oxydized fuel...dry wash media saturation...feedstock...acidy level...any other parameters?
How is the color consistency of your biodiesel?
My bio has been changing to a darker gold...
darker feedstock makes darker BD
Purified fatty acid soaps are almost black in color, Free fatty acids themselves are very dark amber. You can almost follow the removal of soap from the BD as you wash since it will change from a dark amber to a tan gold as the soaps are removed. If I see any hint of amber in my finished BD I immediately suspect that I haven't removed all the soap and rewash a sample to verify this. Sometimes it is soap, sometimes it is just the color of the BD resulting from the oil source.
I think the more double bonds present in the fatty acids in the feedstock, the more yellow the vegetable oil will be. Palm kernel flakes contain less fatty acid double bonds than corn oil, so corn oil has a darker yellow colour. When I melted palm kernel flakes it had little colour to the liquid. It is a light absorption/emission thing. The double bonds in the biodiesel fatty acids is one factor in causing the colour. Thanks
My methyl biodiesel made from new palm kernel flakes is transparent colourless. The biodiesel I made from new corn oil is yellow. The ethyl and propyl biodiesel I made from stearic acid is colourless transparent when it is liquid. The potassium soap I made from palm kernel flakes is white and a solid. There are no carbon=carbon double bonds in stearic acid, I expect that is why it makes a colourless liquid methyl ester. I use new oil to make my biodiesel, so far. Used cooking oil has other stuff in it that contributes to its colour. The acid esterification, base transesterification process produced a darker coloured biodiesel for me. I think in AE the sulfuric acid adds to some of the double bonds in the fatty acids to produce a darker coloured biodiesel that probably has some sulfur in it. The biodiesel I made from acorns is a darker yellow than the biodiesel I made from corn oil. There's a lot of carbon=carbon double bonds in acorn oil.
The color of feedstocks, and the resulting methyl esters are due to pigments in the oil. I don't believe the saturation level of the fatty acid has anything to do with it.
From Food Fats and Oils :
6. Pigments. Carotenoids are yellow to deep red
color materials that occur naturally in fats and oils.
They consist mainly of carotenes such as lycopene, and
xanthophylls such as lutein. Palm oil contains the
highest concentration of carotene. Chlorophyll is the
green coloring matter of plants which plays an essential
role in photosynthesis. Canola oil contains the highest
levels of chlorophyll among common vegetable oils.
At times, the naturally occurring level of chlorophyll in
oils may cause the oils to have a green tinge. Gossypol is
a pigment found only in cottonseed oil. The levels of
most of these color bodies are reduced during the normal
processing of oils to give them acceptable color, flavor,
Here's a link to a pdf of the publication. I've found it to be a useful aid in understanding properties of fats and oils, and the basic reactions that occur in biodiesel production:
Got Renewable Fuel?
The Trouts; Thanks for correcting me. I'm trying to learn more about it.
You're welcome WesleyB
We're all learning together.
Got Renewable Fuel?
Very informative post Bob-thanks for the info
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