Recycle Cardboard

Collected boxes are sorted to separate corrugated cardboard from other fiber grades, then compacted into dense bales for efficient transport to a paper mill. At the mill, the bales are broken apart and fed into a pulper, where water and agitation reduce the cardboard back into a slurry of individual wood fibers.

OCC has a distinct, high-strength long fiber content that makes it valuable for remanufacturing into new corrugated material, so keeping it separate from lower-grade mixed paper preserves that fiber quality and commands a higher price. Baling also compacts the bulky, air-filled boxes into a dense, stable form that dramatically cuts transport and storage costs compared with loose cardboard.

Wax-coated boxes, heavily food-soiled cardboard like greasy pizza boxes, and packing tape or plastic labels are the biggest contamination issues, since wax coatings don't break down in the pulping process and can clog mill equipment, while grease and tape residue weaken and dirty the resulting pulp. Mills typically screen these contaminants out during pulping, but heavily contaminated loads may be rejected or diverted to lower-value uses.

Baled OCC is loaded into a large pulper, essentially an industrial blender, where it's mixed with water and mechanically agitated until the fibers separate into a pumpable slurry. The slurry then passes through screens and cleaners that remove tape, staples, plastic film, and other debris before the cleaned fiber is pressed and formed back into new paperboard sheets.

Recovered OCC is graded under industry specifications, such as those published by the Institute of Scrap Recycling Industries (ISRI), that define allowable moisture content, outthrows, and prohibitive contaminant levels for different grades of recovered corrugated. These grading standards let mills set consistent purchasing specifications and let generators know what sorting quality they need to hit to get top market value.

Recycled fiber requires substantially less energy and water to process than pulping virgin wood, and OCC's long fibers can go through several recycling cycles before losing the strength needed for corrugated board. Given the sheer volume of cardboard generated by e-commerce and retail packaging, OCC recycling markets are also a major economic driver for the paper recycling industry, supplying mills with a lower-cost feedstock than virgin pulp.

No — wax-coated or plastic-laminated boxes, such as those used for produce or frozen food, resist standard repulping and generally aren't accepted by paper mills, while lightly soiled cardboard can usually still be processed after the contaminated portion is screened out. Heavily grease-soaked sections, like the center of a pizza box, are typically torn off and composted or discarded rather than recycled.

Wood fiber shortens and weakens slightly each time it goes through the pulping and papermaking process, and OCC's long virgin fibers are generally considered able to withstand somewhere around five to seven recycling cycles before becoming too short and weak to hold up in corrugated board. That's why mills typically blend recovered fiber with a portion of virgin pulp to maintain sheet strength.

Closed-loop recycling keeps sorted OCC dedicated to producing new corrugated containerboard, preserving its long, strong fibers for a comparable end use and commanding better pricing. When cardboard is instead commingled into a mixed paper stream with office paper, newsprint, and other grades, it loses that fiber-quality advantage and typically gets pulped into lower-value products like paperboard or tissue rather than being made back into boxes.

Sustained growth in e-commerce shipping volumes has pushed OCC generation and recovery rates to record levels in recent years, straining collection and processing capacity at material recovery facilities. At the same time, mills and MRFs are investing in more automated optical sorting to pull contaminants like plastic mailers and wax-coated packaging out of the OCC stream faster and more accurately than manual sorting alone.