Grades A and B represent the virtually 100 percent of paper mill waste that is recycled a back into the milling process. The Environmental Protection Agency (EPA) classifies mill broke (Grade A) as the scraps that are recovered during the paper-making process. (Conservatree 2007, Environmental Definitions) The mills can recycle this at almost zero cost. It is also in the mills' best interest to recycle and re-pulp the unprinted waste (Grade B), as it costs about half of what it costs to recycle post-consumer waste. These two highest grades of recycled paper are both cost-effective and free of contaminants, as it is waste created only by the product production. (Conservatree 2007, Making Paper)
Post-consumer waste is where we find both a greater need for recycling and a high risk of contaminants. Depending on their use, these consumer-used products come back to the recycling plants in various forms, such as envelopes, office paper, newspaper, and magazines, and these forms are often full of contaminants. From address labels and no-lick stamps on envelopes, to colored laser printer paper, to self-stick notes, today's recycled raw materials need a lot of work to go through the system and get back into re-usable paper. (Glass 2000, p. 1) And with the demand for recycled raw materials at an all-time high with the environmental concerns of our modern world, we cannot ask the consumers to remove these hindrances before recycling. The industry must make the consumer want to recycle, and consumers will recycle more the easier it is for them to do so. This puts the removal of contaminants squarely on the paper recycling plants.
The contaminants that cause the most trouble for the plants are the ones that come from adhesive-based materials. These are referred to as "stickies," as they tend to make their way through the filtering process and form into particles that can gum up machines and lower the quality of the pulp. (Glass 2000, p. 1) This is a big problem with the Grade C paper, of which a large amount comes from offices. Having workers sort through this high volume of paper is not cost-effective, so having equipment that is technologically advanced enough to weed out these contaminants is vital.
Fortunately, there is technology available to help alleviate this problem. Older methods of recycling paper into pulp involved using machines that pulverize the raw material with aggressive motion. Often the stickies would disintegrate quickly and make their way through filtering attempts. Today, high consistency batch pulpers and continuous drum pulpers are available, which provide a gentler method of pulping the recycled raw materials. This, in turn, keeps the contaminants from becoming too small and getting lost in