The ability to deink paper – in other words, to separate ink and coatings from it – is crucial for sustainable recycling of it. Good deinkability is a prerequisite for using used paper to make graphical papers and hygienic paper products.
Effective processes are available today for removing aqueous coatings and sheetfed offset printing inks. It is considerably more difficult to achieve good results with UV-cured inks and coatings, the liquid toners used in digital printing, and inkjet inks. Ink that is removed from recycled pulp can be burned to generate energy to run the mill, or sold to make such useful materials as compost or gravel for roads.
A single piece of paper may contain new fibers as well as fibers which have already been recycled once, twice, or several times. Papermaking fibers can typically be recycled 5-7 times before they become too short to be recycled again.
Successful recycling requires clean recovered paper which is free of contaminants such as food, plastic, metal, and other trash. Contaminated paper can introduce impurities and bacteria into the recycling process. Furthermore, different grades of paper – corrugated boxes, newspapers, and office paper – must be kept separate, because the different grades of recovered paper are used to make particular types of recycled paper products.