At the end of Christmas morning, many holiday revelers found themselves sitting cross-legged in the center of an enormous pile of wrapping paper and empty cardboard boxes. Some of that wrapping paper is made of recycled paper. As one Explainer reader crammed her used wrapping paper into the recycle bin for another go-around, she wondered: How many times can a piece of paper be recycled?
Five or six times, on average. At a recycling plant, paper is heated and chopped into tiny bits to make a pulp. During that process, each of the long fibers that characterize virgin paper has an approximately 20 percent chance of being cut into a strand that’s too small to be useful to paper makers. (Short strands of wood fiber make extremely weak paper, and are suitable for newsprint or other applications in which quality is less important.) In theory, a strand could survive the pulping process unscathed for 20, 30, or 100 rounds of recycling, but the odds suggest that a paper fiber only has about five lives.
Even if a paper fiber were to maintain its shape after several instances of recycling, it would still lose some of its virgin qualities. Paper that has been dried and then resoaked in water undergoes a process known as “hornification.” The internal structures contract, causing the fiber to collapse slightly and lose structural integrity. Recyclers usually add virgin paper to a batch of recycled pulp to combat hornification. In addition, paper fibers are often lost in the washing process that separates ink from paper. The paper’s brightness also fades each time it is recycled, which is why some batches of earth-friendly paper have a slightly grayish hue. (On a more positive note, recycled paper often has better opacity than the more porcelain virgin version.)
Since paper loses quality after each recycling, there is a hierarchy that paper descends on its way toward retirement. The fibers that make up a piece of writing paper, for example, may be returned to a notepad if they maintain most of their good qualities. As they age, however, they typically are recycled into something less distinguished, like facial tissues, milk cartons, or toilet paper. The corrugated boxes that carried to your home Christmas presents purchased online will eventually become shoe boxes or cereal boxes.
There’s a good chance you won’t get to see your cardboard box’s next life, no matter what form it takes after rising from the dead. Approximately 40 percent of U.S. waste paper is shipped abroad, often to China, which doesn’t have enough forestland to feed the country’s demand for paper. Waste for recycling is, in fact, the largest U.S. export to China, according to some experts. China’s hunger for used paper is a good thing for recyclers. At times, the price of a ton of recyclable paper has dropped below $5, making the business nearly impossible without foreign demand and government requirements that paper contain a certain percentage of recycled content.
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Explainer thanks Richard Venditti of North Carolina State University.