Handbook of Spent Hydroprocessing Catalysts, Second Edition, covers all aspects of spent hydroprocessing catalysts, both regenerable and non-regenerable. It contains detailed information on hazardous characteristics of spent and regenerated catalysts. The information forms a basis for determining processing options to make decisions on whether spent catalysts can be either reused on refinery site after regeneration or used as the source of new materials. For non-regenerable spent catalysts, attention is paid to safety and ecological implications of utilizing landfill and other waste handling and storage options to ensure environmental acceptance. As such, this handbook can be used as a benchmark document to develop threshold limits of regulated species.