Mass Balance
Mass balance reductions occurring during the repulping and cleaning of recovered paper represent the volume of usable material that is accidentally discarded with the waste. Fiber yield loss measures the percentage of virgin or recycled cellulose that passes through the primary screens into the reject stream. It is a financial metric used to judge the efficiency of a recycling plant.
High contamination levels in the incoming stock typically increase these losses.
Process Waste
Secondary fiber processing involves several cleaning stages where sand, plastic and small metal fragments are removed. During these stages, some healthy fibers are trapped with the contaminants and removed from the system, contributing to the fiber yield loss. Mills attempt to recover these fibers using secondary and tertiary screening loops.
This recovery is limited by the need to maintain the purity of the final pulp. Excessive mechanical treatment can also shorten the fibers and make them more likely to be lost during drainage.
Mill Efficiency
Efficient separation systems keep this loss below three percent in modern mills. Reducing the loss rate directly lowers the raw material cost per ton of paper produced. Automated monitoring helps operators adjust the screen flow to maximize recovery.
