The principal types of paper recycled are old newspaper (ONP), old corrugated cardboard (OCC), high-grade paper, and mixed paper waste (MPW). These waste papers can be classified into bulk or high-grade. The highest grade of papers are manila folders, hard manila cards, and similar computer-related paper products. The bulk grade consists of newspapers, corrugated paper, and MPW. MPW consists of unsorted waste from offices, commercial sources, or printing establishments. High-grade waste paper is used as a pulp substitute, whereas bulk grades are used to make paper boards, construction paper, and other recycled paper products. The heavy black ink used on newspaper reduces its value. The value of paper is also reduced by the presence of other substances that interfere with the single-process conversion into pulp, such as gum in the binding of telephone directories or the chemical coating of magazines.
To ensure quality and minimize handling and processing, ONP should be separated from all other waste at or as close as possible to its source of generation. End users can reject an entire shipment of ONP where evidence exists that the paper was commingled with MSW. Care must also be taken to prevent contamination of the paper during collection, loading, transporting, unloading, processing, and storing.
In MRFs, mixed paper and cardboard are unloaded from the collection vehicle onto the tipping floor. There, cardboard and nonrecyclable paper items are removed. The mixed paper is then loaded onto a floor conveyor with a front-end loader. The floor conveyor discharges to an inclined conveyor that discharges into a horizontal conveyor. The horizontal conveyor transports the mixed paper past workers who remove any remaining cardboard from the mixed paper. The paper remaining on the con veyor is discharged to a conveyor located below the picking platform that is used to feed the baler. Once the paper has been baled, the cardboard is baled.
The Paper Stock Institute of America, which represents buyers and processors of waste paper, has listed thirty-three specialty grades whose specifications are agreed upon by buyers and sellers. Table 10.7.1 gives the specifications for the most common grades of postconsumer waste paper.
The four grades from lowest to highest quality are news (grade 6), special news (grade 7), special news de-ink quality (grade 8), and over-issue news (grade 9). Grades 6 and 7 are used primarily in the production of insulation and paperboard as well as in other applications where high quality (absence of contamination) is not of foremost importance. Grade 8 is used to make newspaper again, as is grade 9. Grade 9 is the grade that sellers find provides the most accessible market.
Paper shipped to a paper mill must meet mill specifications on outthrows and prohibited materials. Outthrows are defined as all papers that are so manufactured or treated or are in such form to be unsuitable for consumption as the grade specified. Prohibitive materials are defined as:
Any material in the packing of paper stock whose presence in excess of the amount allowed makes the packaging unsalable as the grade specified Any material that may be damaging to equipment
The maximum amount of outthrows in grade specifications is the total of outthrows and prohibitive materials. Examples of prohibitive materials are sunburned newspaper, food containers, plastic or metal foils, waxed or treated paper, tissues or paper towels, bound catalogs or telephone directories, Post-its, and faxes or carbonless carbon paper. Other prohibitive materials are foreign materials such as dirt, metal, glass, food wastes, paper clips, and string.
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