Recycling has become successful enough that the paper industry has set a new goal of recovering 60% of paper products by 2012. The success of recycling in America is based on its accessibility on a grassroots level. Almost 90% of the US population has access to curbside or drop-off recycling. Recovered paper then accounts for 37% of the raw material used in American paper mills. About 140 mills use only recovered paper.
Recycling paper is a multi-step process that involves sorting paper, breaking it down into fiber, cleaning it and returning it to a usable pulp. The following section is a detailed look at how used paper is turned into new paper. Here are some examples:
Sorting: Recycling can only work with used paper that is clean and free of contaminants. Paper with food, plastic, metal or other trash is difficult to recycle and may have to be composted, burned for energy or landfilled like trash. Non-recyclable paper must be sorted out from recovered materials.
Storage: Recovered paper is stored in warehouses. Different recycled paper products require different grades of recovered paper. Therefore, various paper grades such as newspapers, office paper and corrugated cardboard are kept separately. When a paper mill is ready to use the paper, forklifts transfer the paper out of the warehouse and onto large conveyors.
Repulping/Screening: The conveyor moves the paper to a large vat, called a pulper. The pulper is filled with water and chemicals. The paper is chopped into small pieces and heated, breaking it down into its component cellulose strands or fibers. As the paper breaks down, it becomes a viscous mixture called pulp. A process called screening is used to filter the pulp. The pulp is forced through screens of varying grades, which clears the pulp of small contaminants such as pieces of plastic and glue.
Cleaning: Spinning the pulp in large, cone-shaped cylinders further cleans it. Light contaminants accumulate in the middle of the cone, while heavier contaminants like staples and paper clips are pushed to the outside and then settle at the bottom. After the contaminants have settled, they are collected and removed.
Deinking: Sometimes the pulp must undergo another cleaning process called de-inking, where ink and other residues are removed. De-inking is usually made up of two processes, washing and flotation. During washing, the pulp is rinsed with water, which carries off small pieces of ink. Afterward, the pulp is fed into a large vat, called a flotation cell, where it is injected with air and surfactants (soap-like compounds). The surfactants loosen the ink and glue, attaching them to the air bubbles, which bring the contaminants to the surface. The air bubbles filled with ink form froth at the top of the vat, which is then removed, leaving clean, usable pulp behind. The froth removed during the de-inking process forms a waste sludge that is environmentally harmful and must be disposed of properly.
Refining/Bleaching and Color Stripping: After being cleaned, the pulp is refined and sometimes bleached. During refining, the pulp is beaten, homogenizing the fibers and making them swell for ideal papermaking. If recovered paper is colored, chemicals are added to strip the paper of dyes. If white paper is being made, it will be bleached with chlorine dioxide, hydrogen peroxide or oxygen. Brown recycled paper, such as found in some napkins and industrial paper towels does not require bleached pulp.
Papermaking: After cleaning and refining, the pulp is ready to be made into paper. Only recycled fiber can be used, or the pulp can be mixed with new wood fiber for greater strength and smoothness. The pulp is then diluted with water and chemicals until it is 99.5% water. This mixture is sprayed in a wide jet across a flat wire screen. Once on the screen, the water drains from the pulp and the fibers bond together, forming paper. See how paper is made.