Editorial Feature

Paper Recycling

Jan 4 2013

Paper, a material predominantly made from fibers, is sold in sheets. Some of these fibers include linen, wood pulp, hemp, cotton, etc. There are many different types of paper available across the world today, including but not limited to painting and water color paper, sketching paper, newsprint paper, print making paper, drawing paper, charcoal paper, wall paper, printer paper, photo paper etc.

The commonly used paper grades include:

Text: This is a high quality paper that can be sized in order to improve the print by lithography
Bond: This paper is mostly used for office copies, letter heads and forms. Made with cotton fiber this paper is suitable for writing using both pencils and pens and can also be erased in a very clean manner
Book and offset: This is a coated grade of paper that comprises good stiffness, dimensional stability and strength
Cover: This paper grade is used as an insert or an outside cover as it is designed specifically for stiffness and higher bulk.

Types of Papers

A variety of papers are currently available and they fall under several different categories that include:

Handmade papers
Printing papers
Drawing papers
Wrapping papers
Writing papers
Specialty papers
Blotting papers

Some of the commonly used paper types include:

Bond paper
Bank paper
Coated paper
Kraft paper
Sandpaper
Wallpaper
Wax paper
Waterproof paper
Construction paper
Book paper

Properties of Paper

The key properties of paper are listed below:

It is now predominantly produced from sustainable and renewable sources and can be recycled and reused
Naturally combustible
It can be enameled, bent, cut, twisted, torn, dissolved, waxed, impregnated, molded and sensitized
Paper can be coated, colored, printed and written on, laminated with metal, plastic and fabric
It can be transparent and opaque
Paper can have a tough texture capable of withstanding acids and a soft texture that can be used on the skin

Manufacturing Process of Paper

There are three significant steps in the manufacture of paper:

The raw material is pulped to obtain fibers that can be used to produce paper
The pulp is brightened or bleached
This bleacher or brightened pulp is then developed into paper.

Cellulose has always been used to make paper. According to conventional methods, the plant containing this natural fiber is cut into tiny pieces and then mashed in water so that the fibers get isolated. This mixture is then poured into a wire mesh mold followed by pressing out the excess water and drying the paper sheet.

To obtain a smooth printing surface and meet other specific requirements some paper products use fillers, coating and other such additives. An increasing number of paper manufacturers currently use wood as a source of cellulose.

Four essential materials are used in the manufacturing process of paper. These materials include water, energy, chemicals and fibers.

Water: Water is used to carry the fibers through all the manufacturing steps and chemical reactions. It also separates organic residues from the pulp.
Energy: The papermaking process involves the usage of both electricity and steam. Energy for this process is obtained from oil, coal, natural gas or hydroelectric power.
Chemicals: Chemicals are used in additives like fillers and coatings to meet the specific requirements of all kinds of papers. Caustic soda is used to clean the recovered fibers. Wood chips are cooked in a chemical solution during the kraft and sulfite pulping process in order to dissolve the lignin that compresses all fibers.
Fibers: Cellulose fibers are the main components in making paper. Lignin, organic glue, is made from flexible cellulose fibers obtained from wood. This glue is found in plenty in softwood trees than in hardwood trees. A number of non-wood plants are also used as raw materials for paper and some of the fibers obtained from these plants can be grouped into agricultural residues and annual crops.

Applications of Paper

Paper is available in so many different forms that broadens the usage of this material in a wide range of areas. The key applications of paper and its various forms are listed below:

Writing, printing, copying etc...
Painting / Art
Posters
Books
Leaflets
Toilet Roll
As filters for medicines, water, air, oil and beer
In the agricultural sector, it is used as seed packets, sacks and animal bedding
Used for identifications and wrapping of electrical cables, battery separators and printed circuits
In buildings, paper is used as decorative laminates for furniture, damp-proof courses, flooring and roofing
It is used for various business and communicative purposes like newspapers, calendars, telephone directories, product manuals, catalogues, etc.
In the medical and industrial sectors, paper is used for wrapping medical instruments to keep them sterile, surgical masks, disposable bed materials and used a protection material for fragile industrial materials like chinaware.
In cars, paper is used as liners for the roof and doors, filters, fascia boards, etc.

Environmental Impacts of Paper

Paper industries use extensive chemical processes on the manufacturing of paper and as result of which an increasing amount of toxic emissions from these industries in turn pollute the water and air. Paper continues to pollute the environment even after it is thrown away after being used. When thrown in the landfill, paper decomposes and produces methane, which is a greenhouse gas that contains high heat-trapping power.

Greenhouse gas emissions continue to exist even when paper is transported to pulp mills and wholesale distributors. Energy is consumed during this transportation process and this leads to greenhouse gas emissions. Chlorinated dioxins also pollute the environment. These dioxins are emitted during the conventional bleaching process.

The growing increase in the usage of paper has led to an increase in deforestation and this in turn has lead to an increase in paper wastage. The best possible way to protect the environment is to recycle paper and reuse it.

Recycling Process of Paper

The first step involves the removal of contaminants like plastic and food from the paper to be recycled. Paper that is contaminated must be burned, composted or landfilled.
At the paper mill, the papers are separated based on their grades as each type of paper can be used to make different recycled products.
The paper is next sent transported by conveyors to a vat called a pulper containing chemicals and water. The recovered paper is cut into tiny pieces by the pulper and when the content in the vat are heated the paper changes into very small strands of cellulose fibers. Pulp is thus obtained as the paper turns into a mixture.
The pulp is then cleaned in cylinders that are cone-shaped. In this cleaning process, heavy contaminants like staples move to the bottom of the cylinder. The lighter contaminants gather in the center part of the cone and are then removed.
The pulp now goes through the deinking process that removes residues like glue, ink and other sticky materials from the pulp. Surfactants are injected into the pulp and these chemicals cause the sticky residues and ink to loosen from the pulp and stick to the air bubbles that float on top of the mixture. These bubbles that form froth are then removed and the pulp is thus clean.
At this point, the dyes are removed from the pulp if the paper is colored and the pulp is further bleached and refined and ready to be made into paper
Chemicals and water are now added to the pulp to form a watery pulp mixture.
This watery mixture is passed through the paper machine that drains the water present in the pulp. The fibers that are recycled now come together and develop into a watery sheet. Water from this sheet is further drained out by placing this sheet under a number of press rollers.
The sheet that looks like paper is now dried by heated metal rollers. A coating mixture is added if a coated paper is required.
The paper is finally wound into a large roll from this paper machine. This big roll of paper is further cut into smaller rolls and recycled paper is thus obtained.

Applications of Recycled Paper

Recycled paper can be used in the following applications:

Throwaways like scribble pads, writing pads, paper used for transmittal and drafting documents
Bulk advertising material and information leaflets
Laser printers and photocopiers
In the domestic sector, recycled paper is used as tissues, table napkins, kitchen towels, toilet paper, lampshades and paper cups and plates