How is whale oil obtained from blubber by rendering?

Rendering is a primary method used to extract whale oil from fatty tissue such as blubber. The process involves cutting or chopping the raw material into small pieces, which are then boiled in open vats or cooked in steam digesters.1

As the tissue is heated, the fat is liberated from the cells and rises to the surface of the water, where it is collected by skimming. The remaining membranous matter, known as greaves, is separated from the aqueous phase using hydraulic or screw presses to recover additional fat. In 20th-century industrial applications, particularly on factory ships, minced blubber was cooked under steam pressure to maximize oil yield, which typically ranged from 50 to 80 percent by weight.12

Modern centrifugal separation methods, developed in the 1960s, improve upon conventional rendering by using disintegrators to rupture cells under controlled temperatures, followed by centrifugation to separate the fat from the aqueous protein layer. This approach yields higher-quality fat and allows the remaining protein to be repurposed.1