Digital printing may have opened doors for people around the world, but next generation inks are creating new problems for the deinking processes that are crucial for recycling paper.
Imagine not being able to decipher the text of your favorite newspaper because the page is just too spotted.
Today in Germany, newspapers rely nearly 100 percent on recycled paper, but paper manufacturers say this resource is becoming increasingly tainted due to the rise of modern inkjet printers.
Though the ink from inkjet printers is water-soluble, it is proving especially difficult to extract from used paper and frequently spoils conventional deinking processes.
"It's like a red sock in a load of white laundry," said Axel Fischer, an expert for recycling digitally printed paper at the International Association of the Deinking Industry (INGEDE).
"The color distributes itself throughout the water, and turns all the clothing pink."
Who put that in there?
In a paper mill, waste paper is dissolved in vats of water. As the water swells the paper, soap is added to help loosen the inks. Air is then blown into the liquid, forcing bubbles containing ink to rise to the surface where the inky-scum is removed.
This process works fine for ink applied with offset printing, the method favored by newspaper and book publishers.
But inks used in digital printing don't percolate to the surface with the air bubbles. Instead, they end up churning through the water and coloring it, producing darkened paper fibers.
It's the same with recycled paper. Once the fibers become too dark, the recycled paper can no longer be printed and must be thrown away.
There are only two methods of deinking paper worldwide. European countries normally employ the froth flotation method. In the United States a 'wash' deinking process is more common.
Both fail when it comes to digital printing inks, albeit to varying degrees.
Dry toners used for photocopiers and some printers are easier to remove from water than inks employed by inkjet printers, for instance. Small amounts of the latter can render deinking impossible.
Particularly worrisome is a fluid ink printing method called 'indigo.' It's used to make photo books, which require a special elastic polymer coating on the paper in addition to the inks. This coating can be even more disastrous for deinking.
"When the paper is dissolved, these layers of film break up into soft, super-thin bits that are flexible enough to slip through the filters and are too heavy for the flotation process," said Fischer.
One German paper manufacturer recently had to dispose of 140 tons of recycled paper after it became contaminated with just a tiny percentage of indigo-printed material.
The problem, said Fischer, is that the paper cannot be properly sorted before the recycling process begins. Humans are unable to tell how something has been printed and devices that could make the distinction have not yet been developed.
For now, Fischer says the only way to deal with the problem is to keep indigo-printed paper out of the mix.
INGEDE has asked paper recyclers not to purchase paper waste from indigo printing companies. Recycled indigo paper should only be used to make corrugated cardboard, Fischer said.
Yet some say there are lower hanging fruit at hand.
"Paper doesn't have to be thrown away just because it isn't suitable for thorough deinking," said Linda Wulff, a sustainability consultant for M-real, a major European paper supplier.
Wulff says there is plenty of room to use darker recycled material for things like toilet paper and cardboard packaging.
"Unfortunately, an opposite trend is underway in Germany," she said, pointing to figures released by Germany's paper manufacturers' association (VDP).
According to the VDP, in the decade between 1999 and 2009 the recovered paper utilization rate of graphic paper, including office paper, grew from 36 percent to 49 percent. For things like tissues and toilet paper, where whiteness isn't a high priority, it declined from 71 percent to 55 percent.
"From an environmental point of view, that just doesn't make sense," said Wulff.
How to solve the problem?
Digital printer and ink manufacturers are now aware of the problem, with some even advertising how they are addressing the challenge.
They say that the deinking process must be adapted to handle modern printing and ink technologies, and they sometimes present new deinking methods they've developed in their laboratories.
Fischer is skeptical.
"Paper-recycling and particularly deinking are not processes that can just be fine tuned a little here and a little there," he said.
The turnover in paper mills is way too high for that, he said, and a yield loss of just one percent would mean a huge loss in raw material and a major increase in garbage at the same time.
Instead, Fischer said companies should create digital printing inks that can be properly removed with current deinking methods.
Another approach could be a special label to certify whether a printer's ink can be removed easily or not.
Austria has introduced such a label. There has been talk of a European scheme, Fischer said, but little has been done to get the project off the ground.
Author: Brigitte Osterath / als
Editor: Fabian Schmidt / Nathan Witkop