Hardwood trees, such as gum, maple and oak, yield short fibers which impart the characteristic of softness to paper. Trees arriving at the mill are first debarked. The bark removed is used as fuel to provide a portion of the mill's energy needs, thereby reducing its reliance on fossil fuels. A typical Georgia-Pacific paper mill uses about three billion pounds of wood chips annually. About 15 tons of useable fiber actually are produced in each cook.
Pulp is produced by the digester after a one to three-hour cook.
The pulp then goes through a multi-stage washer system designed to remove the concentrated mixture of lignin and cooking chemicals. This mixture, called black liquor, is processed to evaporate the water until it is of a consistency similar to grease. This makes it combustible and this mixture is burned as fuel in the mill's recovery boiler. During this process, we recover a wood resin by-product called tall oil which is fractionated for use in the manufacture of paints, adhesives, detergents, shampoos, toothpaste and many other common products. About 95 percent of the cooking chemicals used in the original cook are recovered for use again.