When mills make paper pulp from wood fibers or paper from virgin pulp or recycled pulp, the process uses a lot of water. That water carries away short fibers of paper - lignins and cellulose fibers - that were too short to stick in the paper. The mill wastewater, which also contains clays and other additives, is treated in a wastewater treatment facility (water resource recovery facility or WRRF). The solid residuals from that process are mostly organic matter, with some nutrients. It is a valuable soil amendment.
These light-weight residuals hold water, provide abundant organic matter, and help build deeper organic soils when used in agriculture and land reclamation programs. The benefits include reduced soil erosion, reduced need for irrigation, increased nutrient-holding capacity, and reduced soil compaction.
In New England and eastern Canada, pulp and paper residuals - sometimes called "short paper fiber" or simply "SPF" or "FiberClay" are used in numerous ways:
- in manufactured topsoils: the abundant organic matter improves soils;
- as bedding for dairy and other animals: the fibers and clay absorb moisture and provide padding; and
- in the impermeable cap on closed landfills: the high clay content ensures an impermeable seal.
This video explains (in French) the use of paper mill residuals in Québec:
Pulp & paper residuals being applied with a standard manure spreader to boost the organic matter in this farm soil.
When a pine forest is converted to agricultural use, papermill residuals and biosolids can be applied to boost soil organic matter and nutrients. The result is a better corn crop the first year than the corn crop growing on a long-established farm soil.
See more about use of pulp & paper residuals for land reclamation.