Tackling the Downcycling Issue—A Revised Approach to Value-Corrected Substitution in Life Cycle Assessment of Aluminum (VCS 2.0)

Abstract

For some metals, downcycling appears when scrap is polluted with undesirable elements or mixed with lower quality scrap grades in a way that the material displays a change in inherent properties when recycled. The article recommends the use of different scrap class prices instead of a solitary secondary alloy price to represent the level of downcycling inflicted on aluminum over a product's life cycle. The price ratio between scrap price and primary aluminum price is shown to be stable across all available scrap classes for the years 2007-2010. While the revised approach to value-corrected substitution (VCS) puts a stronger emphasis on the creation of high-quality scrap by penalizing its pollution more than the original version, its key limitation is the correct identification of the appropriate point of substitution along the scrap value chain. If relevant sorting or pre-treatment steps are omitted, the substitution factor would be overcorrected, which is why it is crucial to establish the scrap value right before the scrap is either mixed with scraps from other product systems or right before it enters the remelting step.

Circular economy: To be or not to be in a closed product loop? A Life Cycle Assessment of aluminium cans with inclusion of alloying elements

“…The idea of introducing a downgrading factor to take into account the quality of secondary material versus primary has been introduced in the most recent EoL formula developed in the context of the PEF methodology (Allacker et al 2014). The quantification of the down-cycling issue in modelling aluminium recycling in LCA has already been tackled in terms of economic value of the scrap (Koffler and Florin 2013), but no guideline based on physical properties is available. Our suggestion is to use the outcome of our study to develop an alternative method to quantify the quality or downgrading factor, based on the alloying elements concentration and need for reintegration.…”

Life cycle assessment of resource recovery from municipal solid waste incineration bottom ash

“…For sensitivity, β=1 was assigned to the fine fraction and β=0.35 to the coarse Al scrap. The ratio between scrap prices (instead of secondary aluminium prices) and primary aluminium was proposed by Koffler and Florin (2013) in order to show the level of downcycling reached after a product's lifecycle comes to an end. However, for the sake of consistency within the study, the system boundaries were here not modified according to the approach proposed by Koffler and Florin (2013), so the production of secondary aluminium was always included.…”

“…The ratio between scrap prices (instead of secondary aluminium prices) and primary aluminium was proposed by Koffler and Florin (2013) in order to show the level of downcycling reached after a product's lifecycle comes to an end. However, for the sake of consistency within the study, the system boundaries were here not modified according to the approach proposed by Koffler and Florin (2013), so the production of secondary aluminium was always included. On the basis of the list of scrap class reported by the same authors, possible β for post-incineration scrap was below 0.35, which is the substitution ratio found by the authors for old mixed scrap aluminium.…”

“…The substitution rate for secondary aluminium alloys was indicated by the Greek letter β, and it was defined as: The ratio between the London Metal Exchange (LME) quotation for secondary alloys and primary aluminium (Al 99.7) following the EAA method. In this case, using the aluminium alloy price from the LME, β was set at 0.9 (Koffler and Florin, 2013), and by applying prices for the secondary aluminium EN AB-46000, this ratio was found to be approximately 0.05. Additionally, a differentiation between the qualities of Al scrap in different grain size fractions was made, as quality is related to the grain size of scrap, and different oxidation levels and alloying element content were found.…”

“…A range of substitution rates was defined based on the value-corrected substitution method, as recommended by the European Aluminium Association (EAA, 2013a), and its modifications, as described in Koffler and Florin (2013). The substitution rate for secondary aluminium alloys was indicated by the Greek letter β, and it was defined as: The ratio between the London Metal Exchange (LME) quotation for secondary alloys and primary aluminium (Al 99.7) following the EAA method.…”