Delving Into Deinking

July/August 1993 

How does deinking work, and what does the future look like for this expanding segment of the secondary fiber industry? Here are some answers.

BY KIMBERLEY R. HARRIS

Kimberley R. Harris is associate market analyst for the Institute of Scrap Recycling Industries (Washington, D.C.).

It wasn't long ago that deinking plants were dismissed among the paper industry as dirty places that dealt with inferior grades of paper.

Times have certainly changed. Deinking plants now enjoy high status in the paper industry, thanks to recent market developments: On the supply side, more deinkable paper is being recovered through curbside, office, and business collection programs driven mainly by the public's desire to recycle. On the demand side, many government agencies and businesses have established procurement guidelines that give preference to recycled-content paper products, while major paper consumers such as newspaper publishers are beginning to increase their use of recycled-content stock.

These and other changes promise to boost market demand for deinked fiber and create the need for more deinking capacity in North America . The paper industry, in fact, is already investing billions to not only retrofit existing mills with deinking equipment, but also to build totally new deinking facilities. In the United States alone, there are more than 74 existing deinking plants, representing a total annual capacity of at least 6 million tons, notes the American Forest & Paper Association (AFPA) (Washington, D.C.). In addition, AFPA says, there have been 51 publicly announced expansions or new facilities set to come on-line by 1996, which will likely add more than 4 million tons of deinking capacity. In all, this existing and planned deinking capacity could nearly double the demand for most deinking grades in the next three years, some analysts predict.

The deinking picture is not complete, however, without considering the details of the deinking process itself, whose costs and technical demands directly affect the viability of recycling certain paper grades. Indeed, when it comes to deinking, paper mills face an imposing challenge: to find the most cost-efficient and versatile technology that will enable them to recycle the broadest range of feedstock while also meeting their own strict quality standards, as well as those of their consumers.

Deinking 101

As its name implies, deinking is simply a process that removes most of the ink, as well as fillers and other extraneous materials, from printed or unprinted scrap paper. It's not suitable for all types of recovered papers, of course, but it does apply to more than the recognized list of "deinking grades," according to U.S. paper packers and mill executives. See "Making the (Deinking) Grade," below.

For those grades that are deinkable, deinking is only one part—albeit a vital one—in the multi-step process of transforming scrap paper into recycled pulp. The basic overall scenario begins when paper is dumped into a hydra-pulper, a large water-filled vat often described as a giant blender. The water and the machine's swirling action break the paper down to individual fibers, while chemicals added to the mixture—primarily standard consumer products such as hydrogen peroxide, caustic soda, and talc—set the stage for ink removal by causing the resins and binders in the ink particles on the paper to become water-loving (hydrophilic) or water-hating (hydrophobic), depending on the specific deinking method that will be employed.

The resulting soupy mixture, called a slurry, is then moved through a screening process that removes the larger and heavier contaminants such as staples and paper clips.

The next step, the actual deinking, typically uses one of two technologies—depending on the mill's capabilities and furnish—to produce reusable secondary fiber:

• The wash system—the oldest deinking technology—uses water and chemicals to make ink particles hydrophilic, causing the ink, filler clays, and some coating materials to separate from the fiber and wash away with the water. The wash system's objective is to separate contaminants from the fiber and minimize fiber loss.

• The flotation system makes ink particles hydrophobic and takes advantage of the clay coatings in some scrap feedstock, primarily old magazines, to help remove the particles (for more information, see "Recycling Old Magazines," September/October 1992). Machines called flotation cells, situated at the bottom of the deinking tank, create bubbles in the slurry mix by compressing or aspirating air. The ink attaches to the bubbles and, along with other wastes such as clays, unusable fibers, and contaminants, rises to the surface and is skimmed away with the foaming bubbles. The flotation system is reportedly effective at removing free ink particles—those separated from fibers—but it is said to be less competent at removing fillers and coatings. Another problem is that fiber loss can be greater with this system if the bubble size is too large, paper experts say.

Finally, two hours or so after the entire process began, the slurry passes into a bleach plant and then to a tank, where the mix is stored until it is fed into a paper-making machine, thus completing the recycling loop.

Wastes generated during the process—inks, unusable fibers, clays, and other contaminants—end up in the plant's mill sludge and process wastewater. The sludge is usually dewatered in a press and then landfilled or incinerated, though some mills have found outlets for it as a fuel for waste-to-energy plants and others are experimenting with composting the sludge. The wastewater is usually purged in an on-site water treatment system, then reused.

What's in an Ink?

The deinking process may seem straightforward, even simple, but it must accommodate the myriad variations in recovered papers, which can feature drastically different inks, fillers, coatings, and fibers.

To better understand these variables, consider the raison d'etre of the deinking process: ink. As any paper executive will tell you, all inks are not created equal, though they can generally be classified into four categories: inks that remain liquid and are absorbed by the paper, inks that solidify and lie on the paper's surface, inks that are applied to a coated surface, and inks that fuse with the paper's fibers. These broad categories encompass an array of choices from a slew of different kinds of petroleum-based inks to radiation-reactive inks, metallic inks, magnetic inks, and soybean oil-based inks, each of which possesses various properties, such as higher gloss, better adhesion, resistance to rubbing or heat, and faster drying time. While this potpourri of choices is ideal for ink manufacturers and printers, it can present problems for paper recyclers. Why? Because every time another ingredient is added to an ink's formula, it increases the number of potential complications in the deinking process and raises deinking costs.

Ink variations are so significant that they can determine which deinking process a mill should use, and they can be the deciding factor as to whether deinking is effective on certain papers. Consider such recent developments as non-impact laser printing and water-based flexography: In the former technology, inks are basically nonreactive to chemical removal systems, although the flotation deinking and centrifugal cleaning systems effectively remove this ink (for a discussion on this topic, see "Laser Paper: Gaining Recycling Popularity," November/December 1992). And when water-based flexographic inks are sent through the deinking process, they reportedly disperse into extremely fine particles, diminishing the brightness of the finished recycled paper product. To counteract this problem, mills must bleach the fiber more thoroughly—or live with the ink specks.

Market Matters

Deinking technology is advancing every day, as many paper mills and research groups strive to develop new methods to improve the quality and versatility of both the deinking process and the fiber it produces. One firm, Domtar Inc. (Montreal), for instance, is introducing a new process that can produce a high-quality deinked pulp out of old corrugated containers for use in fine writing papers (see "New Pulping Process Allows OCC Use in Fine Papers" on page 22 for details).

Even with such technical advances, the growth and ultimate success of deinking facilities is tied to the supply and demand fundamentals of the secondary fiber market, which has been struggling through the economic recession of the past few years. Despite encouraging signs of recovery in the paper market at the close of 1992, "there's been a downward spiral since late last year due to the poor U.S. economy," says Thomas F. Bowers Jr., president of Schirmer Paper Corp. (Boston). "The mills just aren't buying scrap paper because mill orders for finished goods are slight." And since finished goods are normally ordered from mills three to six months in advance, packers will have to wait for the next cycle of orders to determine the market's condition, explains Steve Vento, president of the international division of William Goodman & Sons Inc. (Sunrise,Fla.).

Although some factors such as government procurement actions should, in theory, be stimulating demand, Bowers notes, "in reality, these initiatives have not helped the packers' situation at all." This slack demand has meant that neither domestic nor international deinking plants are running at capacity, as had been anticipated.

While the near-term prospects for packers and consumers of deinking grades appear to be smudged, most are optimistic about the market's long-term growth. In light of current efforts to recycle more paper and buy more recycled-content paper products, deinking is almost certain to be a success story with a happy—and prosperous—ending.

Making the (Deinking) Grade

Of the 51 grades of recovered paper outlined in the Scrap Specifications Circular published by the Institute of Scrap Recycling Industries (ISRI), 11 are deinkable according to a consensus of U.S. paper packers. These grades are broken down into two groups.

Bulk material grades:

• Special news—baled sorted, fresh dry newspapers, not sunburned, free from paper other than news, containing not more than the normal percentage of rotogravure and colored sections.

• Special news deink quality—baled sorted, fresh dry newspapers, not sunburned, free from magazines, white blank, pressroom overissues, and paper other than news, containing not more than the normal percentage of rotogravure and colored sections; packing must be free from tare.

• Overissue news—unused, overrun regular newspapers printed on newsprint, baled or securely tied in bundles, containing not more than the normal percentage of rotogravure and colored sections.

Deinking grades:

• Sorted colored ledger—printed or unprinted sheets, shavings, and cuttings of colored or white sulphite or sulphate ledger, bond, writing, and other papers that have a similar fiber and filler content; must be free of treated, coated, padded, or heavily printed stock.

• Manifold colored ledger and manifold white ledger: Sheets and trim of new (unused by consumer) printed or unprinted colored or white sulphite or sulphate paper used in the manufacture of manifold forms, continuous forms, data forms, and other printed pieces such as sales literature and catalogs; must be uncoated and free of laser and office paper, but a percentage of carbonless paper is allowable.

• Sorted white ledger—printed or unprinted sheets, shavings, guillotined books, quire waste, and cuttings of white sulphite or sulphate ledger, bond, writing paper, and all other papers that have a similar fiber and filler content; must be free of treated, coated, padded, or heavily printed stock.

• Computer printout—white sulphite or sulphate papers in forms manufactured for use in data processing machines; must be untreated and coated and may not contain more than 5 percent of groundwood in the packing, but may contain colored stripes and/or impact or non-impact computer printing.

• Coated book stock—coated bleached sulphite or sulphate papers, printed or unprinted in sheets, shavings, guillotined books, or quire waste; a reasonable percentage of papers containing fine groundwood may be included.

• Printed bleached sulphate cuttings—must be free from misprint sheets, printed carbons, wax, greaseproof lamination, gilt, and inks, adhesives, or coatings that are nonsoluble.

• Misprint bleached sulphate—misprint sheets and printed cartons of bleached sulphate, free from wax, greaseproof lamination, gilt, and inks, adhesives, or coatings that are nonsoluble.