This Exploratory Topic seeks to develop technologies for the recovery and reclamation of critical materials (CMs) and other valuable elements from Municipal Solid Waste Incineration (MSWI) ashes. Projects will explore real-time, cost-effective elemental identification techniques for MSWI ash, economically feasible methods of concentrating and extracting elements that may initially be in low concentrations in the MSWI ash, and refining technologies for upcycling scrap metals within waste processing facilities.
The global demand for CMs and other rare metals such as gold, copper, silver, and nickel continue to increase, while production sources for primary ore remains limited. These metals are crucial to the development of technologies across economic sectors, having wide applications particularly in the energy and defense industries. Nearly 2 billion tons of municipal solid waste (MSW) is generated yearly, and some estimates place this feedstock as one of the leading sources for potential recovery of CMs and other metals. While some research has shown that the concentration of CMs and rare earth elements (REEs) to be too low within landfills for significant commercial value, the combustion and gasification processes of incineration of MSW concentrates CMs and REEs high enough to leave a potential for cost-effective reclamation. Teams will focus on both the extraction and concentration process to enable this reclamation process.
Projects Funded Within This Exploratory Topic
GEORGIA INSTITUTE OF TECHNOLOGY
CHARACTERIZATION AND RECOVERY OF CRITICAL METALS FROM MUNICIPAL SOLID WASTE INCINERATION ASHES
Lack of diverse supplies for critical materials, such as rare earth elements (REEs), have prompted researchers to explore new sources and develop environmentally friendly technologies for critical metal extraction, processing, and manufacturing. Municipal solid waste (MSW), a large solid waste stream that may constitute the largest resource for REEs and other critical materials, offers an alternative. MSW incineration ashes, however, pose operational and financial challenges. Georgia Institute of Technology will develop a closed-loop, integrated, scalable, and environmentally friendly waste management and resource recovery system. The system allows for maximum recovery of REEs and other critical metals, production of additional salable products, minimal production of secondary waste, and high immobilization of heavy metal contaminants.
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
ELECTROCHEMICAL MINING OF MSWI ASH
MIT will develop an electrochemical approach to extracting and purifying valuable elements from municipal solid waste incinerator ash, powered solely by electricity from the waste-to-energy plant. The approach is capable of recovering at least 95% of critical materials and at least 90% of other metals while avoiding producing additional hazardous emissions. MIT’s approach uses electrochemical reactions to extract elements that include rare-earth elements and valuable base and noble metals. The proposed technology can upcycle major elements in fly and bottom ash, including calcium and silicon, to value-added products such as lime and silicates for use in construction applications.
VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY
PHYSICAL, CHEMICAL, AND MINERALOGICAL CHARACTERIZATIONS OF MSWI ASH PRODUCT AND RECOMMENDATIONS FOR DOWNSTREAM PROCESSING
Virginia Tech will perform systematic physical, chemical, and mineralogical characterizations on natural and synthetic municipal solid waste incineration (MSWI) ash materials to obtain sufficient characterization results and propose potential downstream processing flowsheets. The team will focus on revealing the conversion mechanisms of valuable metals in MSW during incineration, as well as the occurrence modes, partitioning behavior, and recoverability of critical metals in MSWI ash. A comprehensive and innovative characterization protocol comprised of several methods, such as physical separations, liberation study, and sequential chemical extraction, will be employed.
INTEGRATED CO2-FACILITATED HYDROMETALLURGICAL AND ELECTROCHEMICAL TECHNOLOGY FOR SUSTAINABLE MINING AND RECOVERY OF CRITICAL ELEMENTS FROM WASTES AND ASHES
Critical minerals—used in important defense and energy applications–are scarce. Municipal wastes are excellent candidates for domestic sources of high-grade ores due to their high metal concentration. Because the metals in wastes and waste ashes contain a wide range of impurities, however, conventional extraction processes are not effective. Columbia University will develop an innovative MIDAS process based on the integrated CO2-facilitated hydrometallurgical and electrochemical technology. The team will (1) develop supercritical CO2-based solvent systems for hydrometallurgical extraction of critical elements and metals from waste ashes, (2) explore electrochemical interfaces to refine the extracted metals, and (3) integrate both processes into an energy-efficient process.
USING BIO-INSPIRED LIXIVIANTS TO SELECTIVELY EXTRACT VALUABLE METALS FROM MUNICIPAL SOLID WASTE INCINERATOR ASH
Current environmental, capital equipment, and reagent unit costs of metal extraction and refinement, including from waste minerals, are high. A technical solution will increase the domestic supply of metals as well as reduce consumer cost of downstream power and new technology devices. Lixivia Inc. proposes to use bio-inspired molecules, complemented by conventional chemical reagents to reduce reagent costs, the environmental burden of using such reagents, and the capital equipment needed to produce metals from MSWI ash. Simultaneously, the project will introduce step-change capabilities in metal-selective extraction and refinement from MSWI ash.