waste cooking oil company. Oil renderers The recycling of waste cooking oil (aka restaurant grease, used cooking oil or yellow grease) is a process known as “rendering”. During the rendering process fatty acid is separated from the moisture, the solids and any impurities that are present in the waste cooking oil. The rendering of waste cooking oil produces one usable element and several waste elements. Some collectors do their own rendering while others may sell their grease for a lower price to a company with the space and equipment to do so. Refined used cooking oil is what is left after separation of solids and moisture from yellow grease. Refined used cooking oil is the base for producing biodiesel and renewable diesel. Refined used cooking oil then goes through either to transesterification to produce biodiesel or hydrodeoxygenation to produce renewable diesel. See also Bioliquids Biodiesel Vegetable oil fuel Cooking oil Vegetable oils as alternative energy Gutter oil (counterfeit cooking oil) Fatberg Notes External links "Grease Rustlers" by Susan McCarthy. Salon.com, November 6, 2000. Vegetable oils Recycling Greases