Circular economy: closing the catalyst loop with metal reclamation from spent catalysts, industrial waste, waste shells and animal bones

The future of catalyst will be controlled by sustainable environment and renewability. Presently, most of the catalytic materials are sourced from finite geological deposits. Most of the resources rely up on for catalyst manufacture are dwindling and the accumulation of waste and spent catalyst poses a serious environmental problem and economic sabotage. By recovering catalyst from waste and reclamation of active metals from spent catalyst, the dependence on natural resources that are unsustainable will be reduced, likewise the quantity of materials going to landfill. This work introduces circular economic thinking into catalysis and waste and resource management. The utilisation of industrial waste, waste shells (e.g. seashells and eggshells) and animal bones as a source of catalyst not only provides an economic and environmental protection benefits, but also promotes proper waste management strategy and circular economy. This review stimulates and provides a roadmap for the transition of catalytic science and manufacturing into a circular economy. The major contribution of this work is in the design of green and renewable catalyst from waste materials, and reviews their applications in organic synthesis, hydrogen production from waster-gas-shift reaction and gasification of biomass, biodiesel production, oxidation reactions, selective hydrogenation and pollutant degradation.