Is there a limit to how many times paper can be recycled?

Experiments show that paper fibers can be recycled about five times, says Carl Houtman, a chemical engineer at the Forest Products Lab run by the U.S. Department of Agriculture in Madison. Paper is made up of a bonded network of wood fibers. Processing yanks the fibers apart, breaking off pieces and causing them to lose a little length and stiffness. “Each time you recycle paper, a certain amount of the fiber is lost as sludge,” Houtman says. “The fibers can go around about five times before they turn into ‘fines’ and get washed out of the system.”

Different kinds of paper produce different kinds of fibers for recycling. White office paper makes the highest-quality recycled fiber, but newspaper and magazine fibers are easier to reuse. “In some ways, newsprint and magazine papers are actually more recyclable than white copy paper because the fibers are not as tightly bonded together and so they don’t break up quite as much,” reducing loss of quality, Houtman says. “Newsprint to newsprint is relatively easy.” He adds that there are now efforts under way to turn the bits of wood cellulose lost in sludge into biofuel — arguably, a final recycling step.

(Provided by Bette Thresher from the Clifford Paper Newsletter of 16 May 2011, in cooperation with University Communications.)