There are two distinct methods of extracting oil from the digested material. One system uses mechanical presses and is called the ‘dry’ method. The other called the ‘wet’ method uses hot water to leach out the oil. In the ‘dry’ method the objective of the extraction stage is to squeeze the oil out of a mixture of oil, moisture, fiber and nuts by applying mechanical pressure on the digested mash. There are a large number of different types of presses but the principle of operation is similar for each.