How Screening Can Turn Animal Fat Waste Into Valuable Biodiesel

Almost a third of the fats produced in the U.S. come from animals rather than vegetables. Vegetable oils are more popular and widely used, but animal fat products are actually cheaper to produce. But because of the way they are processed, most animal fats aren't considered to be food-grade, and therefore are not consumable by humans.

The good news is that, through a process of using screener separators and other methods to reduce impurities, animal fats can be purified enough for use as a biodiesel fuel. This is a growing market: Currently, only 3 to 8 percent of the animal fats produced in the U.S. are used to make biodiesel.

Traditional Processing of Animal Fats

Fats like beef tallow, chicken fat and pork lard are used in pet foods and in some industrial processes. To create them, waste fats are rendered, or cooked down until excess water has dissolved.

Then this mostly solid mixture goes through a screw press that pushes out any liquid fat that remains. The fat and the solid, which is known as meat or bone meal, are used for animal feed and items like soap.

The resulting products, however, are typically not suitable for high quality biodiesel. They must be filtered much more carefully to remove impurities.

Issues with Animal-Fat Biodiesel

One issue with using animal fats to make biodiesel is that in colder temperatures, it can solidify. Fuel made from beef tallow, for example, can contain some solids at temperatures as high as 60 degrees.

Another problem that comes from using animal fats is that they can become rancid. Vegetable oils have natural antioxidants that help reduce their rancidity, but animal fats need to have artificial antioxidants added to make sure that biodiesels they are made from will last.

Finally, animal fat is more likely to contain contaminants. This makes biodiesel fuel made from animal fats more difficult to use in engines.

Screening and Separating Animal Fats

In order to solve some of these issues, primarily the problem with contaminants in the animal fat that harm engines, the fats screened to remove phospholipids, or particles that become insoluble in water. This involves passing through high-end industrial screener separators and then centrifuging the material to further eliminate impure material. Sometimes additional steps are taken to ensure purity.

The screening process is also useful to remove any plastics, or polyethylenes, that sometimes end up in animal products. These can come from bags, ear tags or other similar plastic items used to raise, slaughter and process the animal. Plastics in biodiesel can make the fuel cloudy and less efficient.

Screener separators that work to remove very small particles and contaminants are a key to producing biodiesel fuel that won't harm engines or clog fuel filters. Visit a site like for more information.