Paper Recycling Information
Paper recycling has been in existence for longer than many of the newer materials which can be recycled today. Paper recycling takes waste paper and remanufactures it into a new paper product. Feedstock for paper recycling comes in three categories: mill broke, pre-consumer and post consumer waste. Mill broke paper trimmings and scrap from paper manufacturers using virgin material. Pre-consumer is discarded virgin stock paper before it has been used and post consumer is material after it has been used such as the kind paper banks fill with including telephone directories and newspapers.
Paper can be recycled by reducing it to pulp and combing it with pulp from newly harvested wood. As the recycling process causes the paper fibres to breakdown, each time paper is recycled its quality decreases. This means that either a higher percentage of new fibres must be added, or the paper down cycled into lower quality products. Any writing or colouration of the paper must first be removed by deinking, which also removes fillers, clays, and fibre fragments.
Most kinds of paper can be recycled today, but some types are harder to recycle than others. Papers coated with plastic or aluminium foil, and papers that are waxed, pasted, or gummed are usually not recycled because the process is too expensive. Gift wrap paper also cannot be recycled due to its already poor quality.
Sometimes recyclers ask for the removal of the glossy inserts from newspapers because they are a different type of paper. Glossy inserts have a heavy clay coating that some paper mills cannot accept. Most of the clay is removed from the recycled pulp as sludge which must be disposed of. If the coated paper is 20% by weight clay, then each ton of glossy paper produces more than 200 kg of sludge and less than 800 kg of fibre.
How is it done?
There are many different processes used to recycle paper depending on the type of paper to be recycled (corrugated fibreboard, newspaper, mixed office waste) the processes used recycling processes include the following steps:
- Pulping: Adding water and applying mechanical action to separate fibers from each other.
- Screening: Using screens, with either slots or holes, to remove contaminants that are larger than pulp fibers.
- Centrifugal cleaning: Spinning the pulp slurry in cleaner cause’s materials that are denser than pulp fibers to move outward and be rejected.
- Flotation: Passing air bubbles through the pulp slurry, with a surfactant present, causes ink particles to collect with the foam on the surface. By removing contaminated foam, pulp is made brighter. This step is sometimes called deinking.
- Kneading or dispersion: Mechanical action is applied to fragment contaminant particles.
- Washing: Small particles are removed by passing water through the pulp.
- Bleaching: If white paper is desired, bleaching uses peroxides or hydrosulfites to remove color from the pulp.
- Papermaking: The clean (and/or bleached) fiber is made into a “new” paper product in the same way that virgin paper is made.
- Dissolved air flotation: Process water is cleaned for reuse.
- Waste disposal: The unusable material left over, mainly ink, plastics, filler and short fibers, is called sludge. The sludge is buried in a landfill, burned to create energy at the paper mill or used as a fertilizer by local farmers.