L. Reijnders’s research while affiliated with University of Amsterdam and other places

CuO nanoparticles produced by methods from inorganic chemistry and physics are applied as biocides and applications thereof in solar stills, solar collectors, catalysis, sensing and diesel fuels have been proposed. Such CuO nanoparticles are hazardous due to the release of Cu ions and the induced generation of reactive oxygen species after uptake by organisms. Nanoparticle hazard may be reduced by surface modification (coating or capping) and doping which reduces the release of Cu ions and the generation of reactive oxygen species. None of the published safe-by-design modifications of CuO nanoparticles that will be discussed here have been proven safe (no risk). By targeting the release of Cu ions and the generation of reactive oxygen species by CuO nanoparticles, safe(r)-by-design studies target properties that underly the biocidal functionality of CuO nanoparticles. Other functionalities of CuO nanoparticles may also be impacted. There is a case for complementing safe(r)-by-design studies by investigating the impact of the modifications studied on CuO nanoparticle functionality.

Copper ores, end-of-life electric and electronic equipment and car electronics can contain, besides Cu, substantial amounts of geochemically scarce companion elements. Geochemically scarce elements have an upper crustal abundance of <0.025 (weight)%. In view of resource conservation and reduction of pollution there is a case for near-zero waste processing. Improving the generation of ore concentrates and use of kinetic and thermodynamic data regarding smelting and converting can increase the production of geochemically scarce elements in the pyrometallurgical processing of copper ores. Reprocessing of copper ore processing residues can serve the generation of geochemically scare elements and the clean-up of matrix materials. Modularization of products, closed-loop take-back, including deposit-refund, systems for end-of -life products, and changes in the pre-processing thereof can be conducive to improved recovery of geochemically scarce elements from end-of-life electric and electronic equipment and car electronics. A comparatively large variety of geochemically scarce elements originating in end-of-life products can be recovered when in smelting lead and copper serve as collectors. Substantial research and development work is needed to optimize the co-production of geochemically scarce elements by hydrotechnology from copper ores and (mined) end-of-life products and to assess the potential of solvochemistry. There is technical scope for significant progress in the direction of near-zero waste processing in processing copper ores and (mined) end-of-life products, but for the realization of near-zero waste processing there are hurdles to be overcome related to marketability of outputs, safe handling of hazardous elements and company behavior. Also, the techno-economic potential of hydrotechnology and solvochemistry in extracting copper ores, copper ore processing residues and end-of-life products is uncertain. In view thereof, the feasibility near-zero waste production of copper and its geochemically scarce companion elements from copper ores and end-of-life electric and electronic equipment and car electronics is uncertain.

Life cycle assessment (LCA) assesses the environmental burdens or impacts of products from cradle to grave. It is also possible to assess such burdens or impacts for parts of the life cycle. A brief overview is given of LCA methodology. A number of choices have to be made in the goal and scope definition, inventory analysis, and impact assessment stages of life cycle assessments. Such choices can have substantial impacts on LCA outcomes. There are uncertainties in outcomes linked to inventory data and modeling. In the case that future biofuels and production processes are studied, assessment outcomes are characterized by relatively large uncertainties. Choices and uncertainties should be considered in the interpretation stage of life cycle assessments. Methodologies applied to several important environmentally relevant aspects of biofuel life cycles are discussed. These aspects are: emissions of substances impacting climate, depletion of virtually nonrenewable abiotic resources, primary energy demand, and water footprint. LCA can be useful in identifying life cycle stages and processes that are major contributors to environmental burdens, for determining the energetic return on energy invested in biofuels, for the identification of environmental trade-offs, and for comparing the life cycle environmental burdens of products.

As to inorganic and carbonaceous nanomaterials considerable scope exists for a variety of recycling called resource cascading. Resource cascading aims at the maximum exploitation of quality and service time of natural resources. Extension of product use, product reuse, remanufacturing, and the reuse of materials are important elements in resource cascades. Options for resource cascading are available regarding nanomaterials applied in reactors, used as recoverable analyte, and for nanomaterials embedded in, or bound to the surface of, large-sized materials. Important research issues for nanomaterials applied in reactors are: recovery of nanomaterials in commercial processes, preventing aggregation of nanomaterials, kinetics of catalysts and adsorbents and preventing and reversing poisoning of catalysts and adsorbents. Options facilitating extended use and reuse of nanocomposites with large-sized materials include: preventing loss of nanomaterials, preventing poisoning of nanomaterials, preventing degradation of polymers and introducing self-healing properties. For the recycling of nanomaterials and nanocomposite materials a wide range of technologies has been investigated. Performance of thermoplastic polymeric nanocomposites often deteriorates on reprocessing. There is also scope for recycling of nanomaterials and sacrificed nanomaterials present in wastes. There can be good reasons for resource cascading of nanomaterials and recycling of wastes linked to functionality, resource savings and hazard minimization. Much work is still needed to extend our knowledge about options for resource cascading and the minimization of the environmental burden thereof, and to make resource cascading of nanomaterials fully operational.

In their paper about the future availability of copper Henckens and Worrell (2020) assumed that not more than 10% of copper use can be substituted. Here it is argued that currently available data suggest that Cu substitutability might be about 60% or more of current copper use.

Safer-by-design strategies for engineered inorganic and carbonaceous nanomaterials mainly aim at reducing hazard and the release of nanomaterials to the environment. In practice, the focus as to hazard is often on aspects of the overall hazard or specific hazards. Important constraints for safer-by-design are: limited toxicological knowledge, differences between tested nanomaterials and the nanomaterials that organisms or cells are exposed to in the real world, and trade-offs between functionality and safety. Proposed strategies to reduce (aspects of) hazard for nanomaterials include: coating, control of size, doping, grafting, loading, managing shape and crystallinity, reducing the presence of substances at the surface of nanomaterials that contribute to hazard, reduced persistence, and substitution. Isolation of nanomaterials production and processing, in situ synthesis of nanomaterials, enhanced integrity and durability of nanocomposites, design for disassembly of products and efficient recycling of materials may contribute to reducing nanomaterial releases to the environment.

Improving the circularity of our economy calls for easily quantifiable metrics that allow us to track our progress towards circularity. We propose the use of a material quality indicator based on the energy use of recycled products versus their counterparts produced from primary material inputs only. We argue that such an indicator can cover at least the environmental dimension of the circular economy in a sufficient way and is therefore useful for the assessment of the circularity of our economy.