Characterization of Wood Biomass Ash Received from Energy Production Process: Preliminary Assessment of Risk and Valorization Potential for Agricultural and Environmental Applications

Wood biomass ash (WBA) from thermal power plants is often landfilled despite its potential as a secondary raw material. This study adopts a circular economy perspective to assess the physicochemical properties, valorization potential, and environmental risks of WBA, aiming to support its use in agriculture and environmental management. Comprehensive characterization included pH, cation exchange capacity (CEC), proximate and elemental composition, and selected organic contaminants, including polycyclic aromatic hydrocarbons (PAHs). The WBA exhibited a strongly alkaline pH (10.55), moderate CEC (4.36 cmol kg−1), and high ash content (78.32%), with lower nutrient content than other biomass ashes. Major elements included Ca (6.84%), K (2.90%), and Si (3.19%), while nitrogen was absent. Potentially toxic elements (PTEs) such as As, Cd, and Ni were below detection limits; Cr, Cu, Pb, and Zn remained within most regulatory thresholds, although Zn exceeded some limits. ΣPAHs were low (0.05 mg·kg−1), indicating minimal environmental concern. Despite reduced nutrient richness, the ash demonstrated suitability as a liming agent and supplementary nutrient source, provided that Zn levels are managed and nitrogen is supplemented. These results support the redirection of WBA from disposal to beneficial use, advancing circular economy goals and contributing to more sustainable and resilient agricultural systems.