Background, Aims and Scope.
Goal, scope, and background The aim of this work is to present guidance on the application of ISO 14044 to allocation procedures for metal recycling. As such, graphical patterns of metal recycling and generic "rules" for metal recycling maps are presented. The results are intended to be useful in assessing and validating the suitability of allocation procedures for metal recycling in the context of life cycle assessment (LCA) and assist in the understanding of metals flow patterns in product systems. LCA uses a product-focus; therefore, the perspective here is on recycling metals in postconsumer products. The discussions, analysis, and illustrations in this paper emphasize old (post-consumer) scrap and do not detail flows of new (post-manufacturing, preconsumer) or prompt (internal) scrap. The work included participation and review from International Council on Mining and Metals, the Nickel Institute, the International Copper Association, the International Zinc Association, worldsteel (formerly International Iron and Steel Institute), and the International Aluminium Institute. Methods A survey of generic metal flows was conducted for three major non-ferrous metals-nickel, copper, and zinc. Based on the results of this survey, four metal recycling map models were developed. Implications of these recycling maps for LCA were then considered, and parameters necessary to model metal recycling were presented. Relationships of inherent properties and recycling loops are provided and connected to the allocation procedures in the context of LCA. Results and discussion Four metals recycling map models were generated based on a survey and analysis of current metals flow analysis. The utility of the recycling maps is to serve the basis of a structured approach to recycling allocation in life cycle assessment and leveraging the efforts of harmonized recycling metrics. Conclusions A consensus on mapping metals is important in order to achieve an accurate understanding and measurement of metals recycling. To this end, consensus mapping presentation of a general allocation approach and identification of harmonized metrics were achieved among representatives of ferrous and non-ferrous metals groups. Perspectives For the future, allocation factors based on sound empirical data needs to be developed. Those metrics will empower the various stakeholders-industry, policy makers, non-governmental organizations, and academics to make appropriate decisions based on agreed scientific bases.
The criteria persistence (P), bioaccumulation (B), and toxicity (T) are applied by domestic and international regulators and modelers to the hazard identification of chemical substances, including metals and metalloids, that may present harm to the environment. In this paper, we critically examine the literature to determine the weight of evidence for the application of water column partition half-times as a surrogate for the persistence criterion in the aquatic hazard identification of metals and metal compounds. Dissolved metals such as Fe, Mn, Cu, Pb, Co, Cs, Hg, and Zn, as well as the metalloids As and Se, tend to partition from the water column by adsorption onto sinking particulates, with reported and calculated partition half-times in the range 4 to 30 d, with outliers of 0.07 and 280 d. Within freshwater lakes, values of t ½ for the transition metals Cr, Mn, Fe, Co, and Cu averaged about 10 d, while those for the nontransition metals Sr, Zn, Cs, and Hg and the metalloids As and Se varied up to 55 d. These data are consistent with the well-established complexing properties of the transition metals, which are significantly greater compared to the nontransition metals and the metalloids. While the considerable variations in the literature at present preclude the use of metal partition half-times in aquatic hazard identification, the surrogate for the persistence criterion could be the partition half-time of the bioavailable fraction of the total dissolved metal concentration as determined in a laboratory protocol under standardized conditions.
by recommending an approach to and identifying further research for quantifying comparative toxicity potentials (CTPs) for ecotoxicological impacts to freshwater receptors from nonferrous metals. The Clearwater Consensus describes stages and considerations for calculating CTPs that address inconsistencies in assumptions and approaches for organic substances and nonferrous metals by focusing on quantifying the bioavailable fraction of a substance.
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