Unit Operations for Improving the Bulk Properties of Recycled Fiber

Extract

Over the past few years, recycling within the pulp and paper industry has been brought sharply into focus. The primary motivating factors for this have been the crisis in the landfills, of which paper is the largest component, the ensuing legislation, greater public awareness of recycling as an issue, and a desire to recycle more.

In reality, recycling has always been a significant part of papermaking. On a worldwide basis, about one third of the fiber supply is recycled fiber (Table I). A further significant portion of the fiber supply comes from the use of residues from sawmills and other woodworking operations; thus, in the strictest sense, the recycled content is even higher.

The amount of recycled paper that is used varies from 45–50% for Japan and Continental Europe, which have limited forest resources, to about 10% for Canada and Scandinavia, which are rich in forest resources.

In the United States, the recycle rate is about 26% and increasing. Estimates of future usage vary, but the industry as a whole is moving toward a recycle rate close to about 40% or higher by the end of the decade.

It is important to understand the effect that recycling has on fiber properties and also the effect that adding recycled pulp can have on the final sheet properties. To arrive at this, it is worthwhile to review the main aspects of the recycling process and how the process affects pulp properties.