Biodiesel Feedstock Oils

Biodiesel can be made from any plant or animal derived oils. However, some oils are better than others for making biodiesel. We can partly describe oils by the original source, like peanut oil, canola oil, soy oil, beef tallow, and on and on. New oils can also be hydrogenated which alters how they make biodiesel. There are drying oils and non drying oils. Waste oils need more information, like FFA content, and water content.

"Organic oils are three long strings of fatty acids attached to a glycerin molecule. The Fatty Acids can vary in length and in how they are bonded or put together. The way we describe Fatty Acids is by the number of carbon atoms in it and the number of double bonds. We typically see between 12 and 26 carbon molecules in our oils and oils with zero to three double bonds.

Different oils have different blends of fatty acids as you can see from the chart below.

Percentage Fatty Acid Composition of Various Oils

Fat or Oil	12:0	14:0	16:0	18:0	18:1	18:2	18:3	20:0	20:1	22:1
Soybean	.	.	6-10	2-5	20-30	50-60	5-11	.	.	.
Corn	.	1-2	8-12	2-5	19-49	34-62	.	.	.	.
Peanut	.	.	8-9	2-3	50-65	20-30	.	.	.	.
Olive	.	.	9-10	2-3	73-84	10-12	.	.	.	.
Cottonseed	.	0-2	20-25	1-2	23-35	40-50	.	.	.	.
Butter	.	7-10	24-26	10-13	28-31	1-2.5	.2-.5	.	.	.
Lard	.	1-2	28-30	12-18	40-50	7-13	0-1	.	.	.
Tallow	.	3-6	24-32	20-25	37-43	2-3	.	.	.	.
Linseed Oil	.	.	4-7	2-4	25-40	35-40	25-60	.	.	.
Yellow Grease (typical)	.	2	23	13	44	7	1	.	.	.
Coconut Oil	45-53	17-21	7-10	2-4	5-10	1-3	.	.	.	.
Palm oil	.	.	44	5	39	10	.	.	.	.
Palm kernel oil	48	16	8	.	15	3	.	.	.	.
Pongamia pinnata oil	.	.	4-8	3-9	45-71	11-18	.	2-5	10-12	4-5

If you look at the top row, the numbers indicate how many carbon atoms are in the oil, a colon then the number of double bonds. The numbers in the middle of the chart are the percentage composition of the particular fatty acid found in the oils listed on the left.

Each type of fatty acid has a different freezing point, a different tendency to polymerize (dry into a film), and a different energy content.

Nutritional Makup of Various Oils *

Oil	Saturated	Monounsaturated	Polyunsaturated
Canola oil	7%	62%	31%
Safflower Oil	7%	14%	79%
Camelina Oil	10%	33%	54%
Sunflower oil	10%	20%	66%
Corn Oil	13%	24%	59%
Olive oil	14%	73%	11%
Soybean oil	16%	23%	58%
Peanut oil	17%	46%	32%
Chufa oil	20%	67%	12%
Cottonseed Oil	26%	18%	52%
Chicken Fat	30%	45%	21%
Lard	39%	45%	11%
Palm Oil	49%	37%	9%
Butter	63%	26%	4%
Palm Kernal Oil	81%	11%	2%
coconut oil	90%	6%	2%

* note- approximated values - actual values vary depending on the individual plant and extraction methods.

Fatty acids without double bonds are called saturated fats. The lower the saturated fat content, the lower the gel point of the biodiesel made from it.

Fatty acids containing double bonds are called unsaturated. The double bonding site is somewhat unstable and can break off or be chemically altered in the presence of heat and water. Unsaturated fats tend to spoil faster than saturated fats. If an oil contains too many double bonded sites the oil becomes a "drying oil"

Drying oils are not good for making biodiesel as they break down quickly. They usually contain three double bonds per fatty acid. Just to give you an idea, they are used in paints and varnish and dry quickly to form a tough film. Drying oils will age and turn acidic quickly, sometimes the biodiesel made from drying oils will degrade overnight. Examples of drying oils include Linseed oil, Walnut oil, and Poppy oil.

Cooking oils actually make some of the best biodiesel. These are unsaturated oils with a single double bond per fatty acid. Canola is probably the best oil for making biodiesel, since it ages slowly, remains liquid to low temperatures, and has a high energy content. Olive oil is another good oil for making biodiesel. It has slightly a higher gel point, is slightly less stable, and has about the same energy content as Canola oil due to it's slightly increased polyunsaturated and saturated content.

Hydrogenated oils are oils that have been chemically altered to remove the double bonding. This is done to lengthen the shelf life of the oil. While hydrogenated oils are used for cooking oils, they are unhealthy oils for our bodies. In addition it is difficult to make biodiesel from hydrogenated oils. Notice a trend here? The best cooking oils make the best biodiesel. There is a persistent myth on the internet that Chinese restaurants have the best oils for biodiesel, that's true if they use unsaturated, non-hydrogenated oils. Look for restaurants that sell healthy foods and you'll find the best oils. Not only do they use the better oils, but they are more likely to be lower in FFA than other restaurants due to their cooking practices.

Cooking practices play a vital role in WVO quality, primarily on FFA content. FFA or Free Fatty Acids are formed when the long carbon chain breaks away from the glycerin molecule. These fatty acids are acidic in nature and will turn to soap when using our normal base catalyst processing method. They can only be turned into biodiesel if we use Acid Esterification. The soap made from oils high in FFA can cause problems in processing. To make matters worse, FFA are hygroscopic, meaning they attract water. Oils high in FFA can contain as much as 50% water.

If the restaurant cooks at too high a temperature, the oil breaks down quickly and forms FFA. This is pretty simple, high heat makes FFA. They need to keep the oil temperature below 300F for healthy food and good biodiesel.

If the restaurant filters their oil every night before closing, the oil will last much longer. This is due to the fact that the breading and stuff that can be filtered out absorbs water from the atmosphere when the oil is cool, the water then reacts with the oil to make more FFA. Filtering has been shown to keep FFA levels below 1ml titrations for up to a week of heavy use. Without filtering the same oil can reach titration levels of 10 or 15 ml in just a few days.

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How to make your own biodiesel at home

WARNING

Making Biodiesel requires the use of flammable, toxic liquids and strong caustics to make a fuel. No matter what safety precautions are put in place or what equipment you use, making biodiesel will never be a safe hobby and can place you, your property, and your family at risk of injury or even death. Make Biodiesel at your own risk.