Characterization of residues from non-woody pulping process and its function as fertilizer

Pulping and paper industries using non-woody feedstocks face the challenge of its notorious waste disposal problem. To resolve this problem, in this study, we evaluated a variety of properties of solid residues reclaimed from the effluents of both wheat straw ammonium sulfate and Kraft pulping processes as organic fertilizers. The results show that both residues from the ammonium sulfate (RAS) and Kraft pulping (RKP) processes possess desirable C/N ratios, appropriate nutritional compositions, and low levels of harmful heavy metals. The high solubilities (>35 g/L) of both residues allow their use for fertigation or foliar applications. The salt index (30-50) is within the range of commercial chemical fertilizers such as potassium sulfate (42.6) and magnum sulfate (44). The E3/E5 ratios of residues suggest that the residues have small molecular sizes, which are similar to fulvic acids. Overall, wheat straw pulping residues demonstrate the potential as the sustainable organic fertilizers and the beneficial soil amendments. This work has the potential to resolve the severer effluent disposal problem faced by the non-woody pulping and papermaking industries, open a door to effectively utilize residues as value-added byproducts, and lead to both environmental sustainability and economic benefits.