Mill broke

Mill broke is paper waste produced inside a paper mill: off-spec runs, edge trim, sheet breaks. Mills repulp their own broke and feed it back into the wet end, recovering nearly all the fibre.

Sources of mill broke: trim from the edges of the web (the slitter trim), sheet breaks at the dryers or calenders, off-spec startup or grade-change runs, customer returns. All of it goes back into the repulper.

Quality is known: clean, of-known-origin fibre with predictable characteristics, unlike purchased recovered fibre (OCC, ONP) where the input mix varies. Mills can typically run with 5-15% broke content without quality impact.

Mill broke does not appear on shipping manifests because it never leaves the mill. It shows up in mill yield reports and production efficiency metrics — a high broke rate is a sign of process upset.

Related terms

Recycled fibreRecycled fibre is pulp derived from recovered paper: old corrugated containers (OCC), old newspapers (ONP), and mixed paper grades. It is a major input to containerboard, especially for medium and lighter linerboard grades.

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