Forest products have long provided people with food, shelter, clothing, and fuel. Prehistoric people ate berries and nuts that grew in forests. They built shelters from the branches of trees and wore clothing made of plant materials. About 1 1/2 million years ago, they began using wood as a fuel to make fire.
Today, wood is one of our most important raw materials. It is used in making thousands of products, from building materials, to paper, to photographic film. Despite its usefulness as a raw material, the chief use of wood throughout the world is as a fuel.
There are thousands of forest products. Most can be classified into one of five main groups: (1) wood products, (2) wood-based composite products, (3) fiber products, (4) chemical products, and (5) fuel products. Wood products are made from solid wood. Wood-based composite products contain wood and at least one other material. Manufacturers use wood fibers to produce fiber products. Chemical products are made by breaking down wood and wood fibers and chemically treating them. Such chemical products as cellophane, lacquer, and rayon are made from wood but do not feel or look like wood. Fuel products include logs, wood pellets, and charcoal. Other forest products come from the bark, fruit, gum, leaves, and sap of trees.
Wood has many characteristics that make it an important construction material. Carpenters and woodworkers can easily shape it with tools and fasten it with nails, screws, staples, and adhesives. It is light but strong. Wood provides insulation against electric current, heat, cold, and sound. It can hold paint and other finishes, and it does not rust. Unlike metal, cement-based, or plastic construction materials, wood is a renewable resource-that is, a new supply grows after the timber has been harvested. Some of the chief wood structural materials are round timbers, lumber, and veneer products.
Round timbers include pilings, poles, and posts. Pilings driven into the ground provide foundations for buildings, wharves, and other heavy structures. Poles link overhead telephone wires and power lines. People use posts chiefly to build fences. Round timbers are simply trees that have been stripped of their branches and bark, and cut into logs. The logs are dried and treated for protection against decay and insect attack.
Lumber includes boards and larger pieces of wood that have been sawed from logs. In the United States, the construction industry uses about 50 percent of the lumber production. The rest goes to make crates, furniture, railroad ties, sporting goods, toys, and thousands of other products.
Wood scientists classify lumber as softwood or hardwood, depending on the kind of tree. This classification does not always indicate the hardness of the wood. Various softwoods produce harder lumber than do some hardwoods. Softwood lumber comes from needleleaf trees that are also called evergreens or conifers. Builders use this type of lumber for most structural work because of its straightness and length. Softwoods include pine, larch, fir, hemlock, redwood, cypress, cedar, and Douglas-fir.
Hardwood lumber comes from trees that lose their leaves every autumn. Many hardwoods have beautiful grain patterns. For this reason, builders and furniture makers use hardwoods for cabinets, flooring, furniture, and paneling. Popular hardwoods include birch, mahogany, maple, oak, sweet gum, and walnut.
Veneer products are made of thin sheets of wood called veneers. These veneers may be cut into long strips or other shapes. Veneer products include baskets, matches, tongue depressors, and toothpicks.
Wood-based composite products
Manufacturers produce many products using wood together with at least one other material. By combining materials, they can take advantage of the best properties of each. Wood-based composite products include plywood and particleboard, which are made by combining wood with adhesive resins.
Plywood consists of a number of veneers that are glued together. The veneers are arranged so that the grain direction in each layer is at a right angle to the grain direction of the next layer. This arrangement gives plywood several advantages over lumber. For example, plywood shrinks and swells less than lumber, and it can be easily nailed near the edges without splitting. The construction and furniture industries use large amounts of plywood.
Particleboard is made from wood shavings, flakes, wafers, splinters, or sawdust. Some of these materials come from scrap left over in sawmills and paper mills. Particleboard makers mix the wood with an adhesive and press it at a high temperature and pressure to form large sheets or panels. Particleboard shrinks and swells little in length and width. It may be used as a base for flooring and furniture. One type of particleboard, called oriented strand board (OSB), has the strength of plywood and many of the same uses. To make OSB, manufacturers use waxes and resins to bond layers of wood flakes positioned with their grains running in alternating directions.
Other wood-based composite products are made by combining wood with such materials as fiberglass, metals, polyvinyl chloride, polypropylene, and portland cement. Wood-based composites commonly substitute for lumber. For example, laminated veneer lumber is made of parallel laminated sheets of veneer manufactured to standard lumber dimensions.
Wood is made up of many tiny fibers. Manufacturers produce paper and paperboard, hardboard, and insulation board from wood fibers. Wood fiber is also used as attic insulation, as a protective soil covering called mulch, and even as a dietary fiber in breakfast cereals.
Paper and paperboard are made from wood chips that have been reduced to a fiber pulp by chemicals, heat, or mechanical treatment. The pulp is then formed into a mat, filtered, drained, and pressed. Paper products include bags, books, cartons, packaging materials, and tissue.
Medium density fiberboard (MDF) is made from wood that has been reduced to individual fibers or fiber bundles and then been bonded with adhesive. MDF is used primarily to make tops with molded edges for tables or other furniture.
Hardboard is made by pressing wood fibers into flat sheets at a high temperature and pressure. The fibers are held together primarily by lignin, a substance that naturally occurs in and between wood fibers. Hardboard is used chiefly in furniture, siding, and paneling.
Insulation board is manufactured from wood fibers that are formed into a mat, pressed lightly, and dried. It weighs less than hardboard. Insulation board is used for acoustical tile and under siding in construction.
Many wood products are made from wood or bark that has been broken down into such basic chemical parts as cellulose and lignin. Cellulose is the main ingredient of wood fibers.
Cellulose products. Cellulose may be chemically treated to change its properties and to produce such compounds as cellulose acetate and cellulose nitrate. Both of these compounds are used in adhesives, lacquers, and plastics. Plastic items molded from cellulose compounds include piano keys, tool handles, and table tennis balls. Cellulose nitrate is also an ingredient in explosives. Other cellulose compounds have specialized uses in such products as paint, foods, and textiles.
Textile manufacturers process cellulose to produce rayon and acetate fibers, which are used for clothing, draperies, and upholstery. Rayon cords strengthen tires. Other materials made from cellulose include cellophane and photographic film.
Lignin products. Lignin has far fewer uses than cellulose. It is used in making printing inks, dyes, and concrete. Manufacturers use it to bind (hold together) animal food pellets and textiles. Artificial vanilla, a flavoring in many foods, is also made from lignin.
Naval stores include turpentine and rosin-materials once essential to the operation of wooden sailing ships. Almost all naval stores come from the processing of pine pulp.
In many developing countries, wood has long served as the primary fuel for cooking and heating. In industrialized countries, wood has been burned mainly in fireplaces and charcoal grills. After petroleum prices rose in the 1970's, wood became a popular fuel in communities near forested areas. Fuel products made from wood include split, dried logs; compressed wood pellets; charcoal; and sawmill by-products. In addition, the forest products industry burns the thick liquid that results from pulping wood.
Other forest products
Although most forest products are made from wood, some come from the bark, fruit and seeds, gum, leaves, and sap of trees. By-products from sawmills include wood chips, shavings, and sawdust. These by-products may be used in making particleboard and other products, in bedding for animals, and in floor-sweeping compounds.
The bark from the cork oak tree provides cork for such products as bottle stoppers, bulletin boards, and insulation. The bark of the hemlock and other trees furnishes tannic acid used in processing animal hides. Bark is sometimes used as fuel, ground cover, or mulch.
Fruit and seeds harvested from forest trees include many kinds of nuts. The seedpods of the kapok, or silk-cotton, tree provide kapok fibers. Kapok is widely used as a filler in jackets and sleeping bags. Latex is a milky substance produced by plants and trees of the sapodilla family. Latex is the source of natural rubber, which is used to make balloons, hoses, tires, and other items.
The leaves of some forest trees furnish ornamental greenery for Christmas wreaths and similar products. Certain evergreen and eucalyptus leaves are distilled to produce oil used in perfumes, household cleaners, soaps, and certain drugs. Sap from certain kinds of maple trees is made into maple syrup and maple sugar.
The forest products industry
The manufacture of forest products is a major industry in many industrialized countries. The United States, China, and India are the world's leading producers of forest products.
In the United States, the forest products industry employs more than 1 1/2 million people and produces more than $300 billion worth of goods annually. The industry has more than 50,000 manufacturing plants. United States forest products companies own about 70 million acres (28 million hectares) of commercially valuable forestland. They harvest timber in state and national forests under government contracts. They also buy logs from the owners of small wooded areas.
In China, economic reforms that began in 1980 have led to a greater demand for private housing. This demand has, in turn, brought a huge increase in the production of forest products for use as construction materials. In India, millions of people depend on gathering and selling forest products for cash.
Canada's forest products industry is a leading source of export income. More than 350,000 Canadians work for companies that make forest products. Each year, these firms produce goods worth more than $50 billion in U.S. dollars. Canada is the world's leading producer of newsprint, the paper on which newspapers are printed. It produces more than a fourth of the world's total supply each year. Next >>>
Contributor: Jim L. Bowyer, Ph.D., Director, Forest Products Management Development Institute, University of Minnesota.
Source : World Book 2005