Application of wood sawdust microbial transformation for the utilization of long-term stored bark-wood waste

The issue of bark-wood waste (BWW) utilization is challenging for the regions adjacent to pulp and paper mills. Bark is difficult to recycle, and the additives used in paper production further complicate this process. This work focuses on the potential application of wood sawdust microbial transformation, the technology of which was developed at the Irkutsk Institute of Chemistry SB RAS, for the processing of bark-wood waste into environmentally safe soil. Laboratory experiments revealed that long-term stored BWW can undergo microbial degradation. The best results were obtained with the BWW/sawdust mixture. The substrate neutralization conditions were selected to simultaneously lower the pH and introduce the necessary mineral additives for microbial function. A semi-industrial experiment with a BWW/sawdust mixture of 20 m ³ (3:1 ratio) was performed. The experiment demonstrated that pH stabilization occurred more efficiently than in the laboratory experiment. A temperature increase, which is characteristic of aerobic processing of lignocellulosic waste was also observed. The product obtained was non-toxic to both plants and Chlorella vulgaris (hazard class 5). The processing improved of the agrochemical parameters of the substrate, such as hydrolytic acidity, cation exchange capacity, and the sum of absorbed bases. The increase in humic acid content indicates a deep microbial degradation of the lignin component of BWW. Consequently, the microbial transformation of BWW was successfully implemented to produce a non-toxic soil. This technology can be scaled up for large volumes of BWW at storage sites.