How do recycled paper and cardboard become sources of paper pulp?

Recycled paper and cardboard are transformed into paper pulp through a systematic process of collection, sorting, and mechanical pulping.

Collection and Sorting

Wastepaper is gathered from various sources, including industrial establishments, offices, and households. Because contamination by foreign materials—such as plastics, adhesives, and metal foils—complicates the process, effective sorting is essential. Materials are often separated at the source or at a centralized material recycling facility to ensure quality.123

The Pulping Process

Once sorted, the paper is fed into a pulper, a large tank equipped with agitator blades. Hot water is added to the stock to help separate and disperse the fibres. The recovery process then follows one of two paths:1

• De-inking: Used for printing-grade or white papers, this process involves adding chemicals—most commonly caustic soda—to remove ink and contaminants. The stock is then screened, washed, and sometimes bleached to improve whiteness.12
• Non-de-inking: Used for boxboards and coarse papers, this method skips the chemical de-inking stage. The stock is simply screened and washed to remove dirt and trash.1

After these steps, the resulting pulp is ready to be processed into new paper products.2