talking trash

The Why Files scouted around for some smart new ways to recycle paper and other wood materials:

Getting loaded
White printing and writing paper is actually a blend of wood fibers and a cheaper filler that makes it smoother and brighter. Unfortunately, too much filler weakens the paper by interfering with the bonds between paper fibers. Now, U.S. Forest Products Laboratory (FPL) scientists have found a way to cram filler inside the paper fibers, so more filler can be added to recycled pulp.

    shredded paper feed paper

Scrap paper is fed into an experimental pulp-maker.

That could increase the value of mixed office waste, a growing category of recovered paper, by brightening the paper and concealing residual ink, according to John Klungness, an FPL chemical engineer.

The filler in question is calcium carbonate, which is traditionally applied to paper fibers in a slurry. The FPL researchers add calcium hydroxide to the pulp. When they pump in carbon dioxide, a chemical reaction forms calcium carbonate particles inside the paper fibers. In this location, the filler harms the bonding less than conventional loading techniques, so more filler can be used.

The calcium carbonate crystals visible inside and outside these hollow paper fibers improve paper brightness and make it easier to recycle.

Photos courtesy of U.S. Department of Agriculture, Forest Products Laboratory.

now put on your thinking caps!

  carbonate crystalsBut there are more advantages: The combined savings in energy and raw material should enable the process to return its capital costs in less than two years, Klungness says. And the resulting paper should be cleaner to recycle when its time comes. That's important since making pulp from recycled paper produces two to four times as much sludge as making pulp from pulpwood.

(Speaking of repeat recycling, Klungness says the paper industry's goal of recycling 50 percent of discarded paper by 2000 is "within reach," but that this could be the practical limit. The reason? Paper fibers lose strength with each recycling, and fail after seven cycles. As the overall recycling percentage rises, so does the proportion of fibers that have been recycled seven times. Corrugated cardboard can be recovered at higher rates because the recycling technique is less injurious to the fibers.)

Enzymes zap ink from recycled paper
To manufacture pulp from recycled paper, you've got to get rid of the ink and toner on the old paper. Existing processes do that job with high temperatures, plenty of mixing energy, and caustic chemicals. But the FPL has developed a way to use enzymes (naturally produced chemicals that trigger specific chemical reactions) to do the same job without fuss or muss.

After four years of development the technology is being used in extended industrial trials, ands is "on the verge of acceptance," says Klungness. Its advantages include lower cost and less sludge to dispose of. There's also a possibility the enzyme could be combined with the new filler technique we just saw.

From railroad trestle to backyard furniture
When the Southern Pacific railroad built a short-cut through the Great Salt Lake in 1901, it did the obvious thing: the railroad selected cheap, knot-free redwood for the ties and planking. The 12-mile trestle was finally replaced in 1959, and torn down in 1993. That act of demolition produced a treasure-trove of clear redwood -- 207,000 board feet.

If you could find that wood on the market, it would cost a fortune. And although you can't find it on the market, you can buy the wood in tables, chairs and other garden furniture -- from the Trestlewood Furniture Company. Trestlewood plans to expand into other recycled wood items when its supply of redwood is exhausted.

Rebirth act for ceiling tiles
While we're plumbing this wood-fiber recycling theme, think about those cellulose ceiling tiles (if you're in an office, just look up). These ubiquitous tiles eventually fade, but since painting them reduces their ability to deaden noise, old tiles typically make a major migration to dumpster-ville.

Faced with the prospect of trashing almost 4 acres of ceiling tiles in a building project, a determined Seattle construction company convinced Armstrong Ceiling Tile Company to recycle the old tiles into new tiles. The project worked. Armstrong will now recycle old tile for any project on which new Armstrong tiles are used. (See "C&D Management..." in the bibliography)

Want to cycle through our use-it-again bibliography?


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