Mass Ratio
Dry mass recovery of usable cellulosic material relative to the starting bone-dry weight of raw wood or non-wood furnish measures conversion efficiency in pulping and recycling processes. Raw furnish components undergo varying degrees of chemical degradation and mechanical dissolution, establishing fibre yield as the governing mass balance factor in pulp manufacturing. In kraft chemical pulping, deliberate extraction of lignin and accessible hemicelluloses drives recovered mass down to approximately forty to fifty percent of starting wood solids.
Neutral sulfite semi-chemical pulping retains significant lignin and carbohydrate fractions, shifting recovery to a typical range of seventy to eighty-five percent. Mechanical pulping delivers recovery rates above ninety-five percent because physical attrition preserves almost all wood constituents except water-soluble extractives. In recovered paper processing, mechanical screening, flotation deinking, and washing reject non-fibrous fillers, inks, adhesives, and heavily damaged fines, establishing an operational recovery factor below incoming bale mass.
Pulping Chemistry
Delignification selectivity during digestion controls the destruction rate of structural polysaccharides. Strong alkaline white liquor dissolves lignin through nucleophilic cleavage of ether bonds, yet peeling reactions degrade cellulose chains from their reducing ends until stopping reactions occur. Anthraquinone additions suppress carbohydrate degradation by oxidising reducing ends to aldonic acids, lifting final recovery by one to two percentage points on dry wood.
Polysulfide liquor modifications similarly oxidise cellulose and hemicellulose chain ends, protecting glucomannans from endwise alkaline degradation. Higher cooking temperatures and extended retention times systematically lower total recovery by accelerating cellulose hydrolysis.
Paperboard Economics
Furnish costs in board manufacture scale directly with pulp mass recovery because low-yield chemical fibres demand higher wood consumption per finished metric tonne. Bleached chemical pulps impart superior tensile strength and optical brightness, yet their low mass conversion inflates furnish expenses relative to high-yield mechanical stocks. Fluting mediums rely on semi-chemical or recycled stocks where high lignin retention sustains structural stiffness and flat crush resistance at lower production cost.
Mill operations continually balance stiffness targets against recovery percentages, using refining energy to restore bonding potential lost from high-yield, rigid fibres.
