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• We modelled prospective life cycle impacts of aluminum production sector up to 2100. • SSP narratives are leveraged to model technology penetration and grid mix evolution. • We forecast global carbon intensities from 8.6 to 18.0 kg CO 2 eq/kg as baseline. • Majority of improvements result from policy in the energy sector. • Absolute sector-wide CO 2 reduction is realistic with aggressive policy efforts. Aluminium is an energy intensive material with an environmental footprint strongly dependent on the electricity mix consumed by the smelting process. This study models prospective environmental impacts of primary aluminium production according to different integrated assessment modeling scenarios building on Shared Socioeconomic Pathways and their climate change mitigation scenarios. Results project a global average carbon intensity ranging between 8.6 and 18.0 kg CO 2 eq/kg in 2100, compared to 18.3 kg CO 2 eq/kg at present, that could be further reduced under mitigation scenarios. Co-benefits with other environmental indicators are observed. Scaling aluminium production impacts to the global demand shows total emission between 1250 and 1590 Gt CO 2 eq for baseline scenarios by 2050 while absolute decoupling is only achievable with stringent climate policy changing drastically the electricity mix. Achieving larger emission reductions will require circular strategies that go beyond primary material production itself and involve other stakeholders along the aluminium value chain. [ABSTRACT FROM AUTHOR]

• A combined MFA, MCI & LCA approach is proposed to assess material efficiency and environmental performance at different scales. • Maximizing recycled content into bottle production is not necessarily environmentally preferable than open loop recycling. • Increasing post-consumer bottle collection rate is key. • Material circular strategies at product level should be assessed at the largest scale to account for broader system dynamics and avoid burden shifting. The Circular Economy (CE) movement is inspiring new governmental policies along with company strategies. This led to the emergence of a plethora of indicators to quantify the "circularity" of individual companies or products. Approaches behind these indicators builds mainly on two implicit assumptions. The first is that closing material loops at product level leads to improvements in material efficiency for the economy as a whole. The second assumption is that maximizing material circularity contributes to mitigate environmental impacts. We test these two assumptions at different scales with a case study on the circularity of PET in the USA market. The Material Circularity Indicator (MCI) reveals that closing the material loops at the product level increases material circularity in one brand and in the USA plastic bottle market but not in the USA PET market as a whole. Life Cycle Assessment (LCA) results reveal that increasing closed loop recycling of PET bottles is environmentally beneficial from product-level assessment scope. When expanding the scope to the whole PET market, recycling PET into film, fiber and sheet industrial sectors results being more material efficient and environmental preferable, unless the postconsumer reclamation rate is significantly improved. Thus, we demonstrate that adopting a systemic approach for CE assessment is essential ; instead of looking at one particular product and seeking the best circular case with respect to a specific material content, we suggest to looking at the whole set of products served by the specific material, and to seek the best material market-wide circular case. Image, graphical abstract [ABSTRACT FROM AUTHOR]