The use of cellulose nanofibers (CNF) as an additive in papermaking is an attractive alternative to improve paper's strength. However, the costs of CNF production need to be competitive compared to other approaches aimed at reducing mechanical beating. Five different types of CNFs were prepared following different pretreatments: TEMPO-mediated oxidation at basic and neutral conditions, soft acid hydrolysis, enzymatic treatment, and mechanical beating. All of the pretreated fibers were later passed through a high-pressure homogenizer. The resulting CNFs were each applied to a papermaking pulp to investigate their reinforcing ability. Results indicated that the TEMPO-oxidized CNFs offered the highest increase at the same nanofiber content compared to the other types of CNFs. However, an analysis of the cost of increasing paper's breaking length by 75% indicated that TEMPO-oxidized CNFs were more expensive than the other CNF grades, whereas CNFs from mechanical and acid pretreatment offered similar increases at lower prices. The results indicated that CNFs of high fibrillation degree were not necessary to induce dramatic increases in paper strength. This finding offers a new possibility for the escalation of CNF production to industrial levels with competitive prices.

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