Over at Packaging World, a consideration of the pluses and minuses of the use of recycled paper fiber in corrugated boxes. First of all, as the author points out, corrugated boxes made from 100% virgin fiber are pretty non-existent, but what is the optimal percentage of post-consumer fiber? It could be argued that the lowly box has no need to contain any virgin fiber. After all, it’s just a box, right? Well, let’s not give the box short shrift—or even short fibers. As the article points out, virgin fibers contribute two important elements to a package: strength (recycled fiber is not as strong as virgin) and aesthetics, in the form of substandard performance on press, inks that run, labels that do not adhere properly, etc. The aesthetics of packaging are important when the package has to serve as the product “salesman” (or “saleswoman”; I don’t know how one sexes a box, nor do I really want to). The consequences in terms of sustainability?
The use of recycled-content corrugated boxes that underperform the aforementioned functions is the opposite of sustainability; for, when products aren’t sold because the packaging didn’t adequately protect or didn’t adequately persuade, all of the resources and energies consumed in the sourcing, manufacturing, and distribution of those products are squandered.
Of course, not all corrugated boxes need to be superstrong; if you’re shipping pillows or Nerf balls, you can get away with a weaker box than if you were shipping computers, TVs, or weightlifting equipment. As for aesthetics, there may be in inner package that does the real selling, or the product may be sold online, where aesthetic packaging is irrelevant.
From a sustainability perspective, there is an inherent appeal to reducing the use of virgin feedstock.  But sustainability is best evaluated through a holistic lens—whether that’s Life-Cycle Assessment, Cradle-to-Grave Analysis, or something similar.  Conducting those evaluations for reliable results is a formidable undertaking under the best of circumstances; however, the degree of difficulty is notched up when it comes to recycled fibers and the corrugated boxes that incorporate them.  That’s because a box’s recycled content is citable on a percent basis but not on a composition basis.  A box can be said to contain a specified percent of recycled content, but the exact makeup of that content is—for all intents and purposes—unknowable.
That is, fibers lose length and strength each time they are recycled, so paper fibers that are on their third, fourth, fifth go-round may be well-nigh unusable—think of a third- or fourth-generation photocopy. So when you have no idea what generation the recycled content is, you really have no idea how strong the box is, or what its performance properties are going to be. So
specifying a given percent of recycled content doesn’t guarantee consistency of the composition of that content, meaning that it doesn’t guarantee consistency of quality and performance.  Not only do boxes differ across suppliers, they differ from the same supplier.  That lack of standardization makes the use of standardized tests, such as Mullen and Edge-Crush Test, less reliable, in addition to imposing difficulties for organizations that certify corrugated boxes.
Recycled content will never completely supplant virgin, at least not anytime soon, simply because there isn’t enough of it. And, as we can see, we really don’t want recycled to completely replace virgin. Finding the best balance between the two—and developing effective metrics to determine the quality of the recycled fiber—should be the objectives in this area.