Chemical Risk Assessment in Black Mass Processing Facilities: Addressing Safety in a Critical and Emerging Industry

Black mass (BM), the key intermediate product in lithium-ion battery (LIB) recycling, exhibits a complex hazard profile due to its heterogeneous composition, fine particle size, and reactive electrolyte residues. Despite its industrial relevance and recent classification as hazardous waste under EU Regulation 1357/2014, a structured chemical risk assessment (CRA) framework tailored to BM-handling facilities is still lacking. This study introduces the first scenario-based CRA methodology developed specifically for BM processing environments. Seven representative operational scenarios were defined to cover the complete BM lifecycle, from battery collection and preliminary storage to mechanical treatment, hydrometallurgical processing, thermal operations, and laboratory-scale activities. For each scenario, chemical hazards were identified using CLP hazard statements and BM composition data, while probability and severity were quantified through a semi-quantitative matrix aligned with ISO 31010 and EN ISO 12100. Application to two representative case studies, laboratory-scale BM handling and industrial BM production, demonstrates the contrasting nature of risks across operational contexts. Laboratory operations are dominated by high exposure probability due to manual handling of powders, whereas industrial scenarios exhibit lower frequency but higher severity linked to combustible dust formation, HF release, and mechanical ignition sources. The framework enables prioritization of hazards, supports targeted mitigation, and provides an operational basis for BM-specific safety protocols. As the EU Battery Regulation expands recycling obligations, such tailored CRA approaches will be essential for ensuring the safe and sustainable scaling of BM processing.