Physicochemical Assessment of Plant-Derived Residues as Potential Components of Substrates for Pleurotus ostreatus Cultivation

Plant-derived residues may provide locally available components for mushroom cultivation substrates, but their variable composition requires preliminary physicochemical characterization. The aim of this study was to evaluate the physicochemical parameters of selected plant-derived residues in terms of their suitability as substrate components for the cultivation of Pleurotus ostreatus. The primary raw materials used were: oak sawdust, birch sawdust, wheat straw, triticale straw, rapeseed straw, and hemp shives. In addition, spent coffee grounds and apple pomace were applied as supplements enriching the substrate. The tested materials were subjected to physicochemical analyses including the determination of pH value, nitrogen, phosphorus, potassium, magnesium, calcium, sodium, organic carbon, and heavy metal content. The lignocellulosic materials showed high C:N ratios (80–257), indicating the potential need for nitrogen supplementation. Spent coffee grounds had the highest nitrogen content (21.61 g·kg−1 DM) and the lowest C:N ratio (25.96), while apple pomace showed the lowest pH (3.85). Wheat and triticale straw supplemented with spent coffee grounds were identified as promising candidates for further cultivation trials, supporting the valorization of plant-derived residues in line with circular economy principles. As the study was limited to preliminary physicochemical screening, lignocellulosic-fraction analysis, physical characterization, and cultivation trials are required before the technological suitability of the proposed mixtures can be confirmed.