Reprinted with permission from the Datek Imaging Supplies Monthly 4(2) Feb. 1990, p. 4-5. A sidebar listing major U.S. sources of deinking systems is omitted.
One critical feature of the recycled paper story is "deinking," the process that removes inks from post consumer wastes such as old newspapers and office refuse. In 1989, a year in which levels of paper recycling reached new highs, deinking proved to be a bottleneck, with demand outstripped capacity in some areas. Major deinking capacity now exists at less than a dozen sites in the U.S., although there is growth in the field and plans for new additions receive quick attention in paper journals.
In terms of waste that must be deinked, office waste ranks behind old newspapers, but it is a significant source of recoverable fibers, and a large share of it contains paper that has been imaged in whole or in part with toner. For the mills, toner is a problem ink, polymer-based and heat-fused to the wood fibers. It is difficult to separate from the pulp, and tends to clump into large particles.
By contrast, most offset--and impact ribbon inks--have organic bases, such as linseed oil, and are easily separated. As a result, toner-contaminated wastepaper sells for a notable discount, with laser-imaged stocks selling for up to $150 per ton less than paper printed by offset or impact printers. Mills that have deinking avoid purchasing large quantities of stocks in-aged with toner. In sum, toner can be removed from wastepaper by existing processes , but doing so requires are tire and effort, and is less economic.
To review established deinking methods, they fall into three categories: washing, flotation, and dispersion. Washing is the traditional U.S. approach, a comparatively simple combination of outer and special detergents that works well with newsprint, where cheap inks can be removed from the pulp easily. More involved are flotation processes, which, traditionally have been more widely used in Europe: not as water intensive as washing, flotation relies on physical and chemical processes that in effect attach bubbles to granules of ink, which then float to the surface to be skimmed off. Both washing and flotation methods are able to handle most impact ribbon inks, in addition to a range of offset inks.
Dispersion is a third process, an add-on to flotation or washing, that employs physical or chemical means to deink pulp. It also breaks up toner particles and reduces their size to accommodate their removal by washing or flotation. To remove toner, dispersion usually connotes heavy equipment: an installation big enough to handle 200 tons per day may cost more than $1 million.
The amount of extra time and processing that toner requires of the deinking process is hard to quantify because, with the exception of newsprint, most wastepaper is inconsistent in terms of composition. Wastepaper with a higher percentage of toner-fused pages will obviously require more processing, usually including dispersion, and extra time in one or more deinking processes.
One alternative for handling the toner problem is a deinking process marketed by PPG Industries (Pittsburgh, PA; 412/434-2137). PPG's approach involves the addition of proprietary deinking compounds, which loosen toner particles, causing then to clump into 2-3m granules that do not adhere to wood fibers, for later removal by filtration.
PPG says its deinking system (chemicals only, no hardware) is less expensive than conventional methods. It is normally combined with the centrifugal equipment widely used to control particle size in the pulp furnish. Although the process has been much discussed, it has yet to be widely adopted by the conservative paper industry. PPG notes, though, that the critical first client has been established, and that the PPG process is in use, with good results, at one mill.
The price of deinking--PPG's system or any other--is a key to the recycling of post-consumer waste. Not all current financial indicators point to greater adoption of deinking. For the paper industry's non-integrated mills, deinked pulp is still a good buy, but for integrated mills, which may come to dominate the industry, virgin pulp is often more economical. Obviously, there are other forces favoring recycling, such as consumer interest and environmental legislation. For these forces to gain the end they seek, though, recycling advocates will have to pay more attention to such obscure but important topics as deinking