The Paper Cycle

As human civilization developed, a need arose to record thoughts and events on some desirable material. Initially, rocks, bones and animal skins were used for this purpose. Eventually, thinner and flatter materials took their place. In ancient Egypt, woven papyrus was commonly used as "paper," while cloth, woven from silk or linen, predominated in the Orient.

The Chinese were the first people to make paper by pulping (beating and mixing with water) instead of weaving. They used pieces of cloth which were shredded, cooked in water and then pounded into a pulp. The pulp was spread onto a screen to dry, thus resulting in a thin paper. This procedure was first used in about 100 AD.

Making paper from cloth continued into the mid 1800's. The invention of the printing press, however, increased the demand for paper dramatically. Despite efforts to collect rags and old clothing (an early example of recycling), the supply of cloth could not keep pace with the demand for paper. A material in more plentiful supply was needed.

Wood was tested as a replacement for cloth and found to be satisfactory. In theory, making paper from wood is similar to making paper from cloth. There are a few additional steps:

• Transport
  Trees are felled and transported to the paper mill. Usually, "softwoods" such as pine and spruce are used to make paper due to their long, strong cellulose fibers.
  
  
• Tumbling
  The lots are cut into 4 to 8 foot lengths and stripped of their bark. This is accomplished by tumbling or spraying with water. The wood is then chipped into small pieces.
  
  
• Digester
  The chipped wood is then cooked in a large pressure cooker called a digester. Chemicals are added and the lignin is removed. Lignin is a resinous substance that helps bind the wood fibers. If not removed, the lignin would cause the paper to turn yellow as it ages.
  
  
• Pulping
  The resulting mixture is then treated chemically and mechanically beaten to form pulp. Pulp is a mixture of water and wood with the consistency of oatmeal. The pulp is spread thinly onto a moving screen and run through a series of rollers and dryers. This removes excess water before the paper is wound into large rolls. The rolls of paper will be used by a manufacturer to make a variety of paper products and packaging.

Recycling paper involves basically the same steps as producing paper from wood.
After collecting used paper, it is sorted according to its type or grade. There are dozens of paper grades including newspaper, white ledger and cardboard. Most grades of paper are recyclable, but separation according to grade is desirable to increase the value.

"Small Planet" Monterey Regional Waste Management District School Education Program.