Measuring the Performance of Closed-Loop Product Manufacturing Systems: Increasing the Material Circularity while limiting the Environmental Burden

A shift to circular economy presents the challenge of recirculating material flows in a manner that can promote eco-effectiveness. Different strategies exist for the preservation of resources such as repair (preserving the product as a whole), refurbishment (preserving the use of components) or, as a last resort, recycling the materials. While material recycling is considered the least effective restoration strategy for end-of-use products, it is a key part of industrial symbiosis that aims to re-circulate material flows by preventing by-products to become waste trough industrial waste valorisation. While there might be some competition in the short term, these different CE strategies can complement each other in the long term because they act at different stages of the product lifecycle. First, in order to measure the product circularity and quantify the effectiveness of different CE strategies, a new circularity indicator, the Product Circularity Indicator (PCI), has been developed. The indicator can be used to measure the implementation level of CE strategies in product value chains. The results showed that in most case an increase of product circularity also improves the product's environmental performance. However, selecting more recyclable materials such as steel instead of concrete can increase the overall environmental burden and the circularity assessment does not take into account the energy consumption during the product's use phase. Therefore, potential trade-offs between increasing circularity and minimizing environmental burden should always be investigated. Second, the potential benefits of manufacturing waste valorisation strategies are evaluated. The results of this dissertation show that implementing enhanced aluminium scrap sorting strategies at manufacturing companies can have substantial benefits in term of (1) increasing the recyclability of the generated scrap and (2) increasing the recycled content of aluminium wrought alloys. While the improved sorting strategy significantly increases the circularity indicator score of the aluminium supply chain, special attention must be spent to the scrap availability and utilisation. Indeed, in some cases the required scrap exceeds the available volume and in other cases a scrap surplus is generated. Nevertheless, in all cases, an enhanced sorting system reduces the environmental burden associated with the use of wrought alloys Third, an assessment method for product repairability is proposed because extending the product life through increased repair is one of the most effective CE strategies at product level. Based on identified barriers and relevant product features for repair, a set of repairability criteria are proposed in the Assessment Matrix for ease of Repair (AsMeR). Further analysis of recently developed methods to assess product repairability demonstrates their ability to reflect the diversity of the analysed product models. The presented research has also investigated the influence of methodological choices such as criteria selection, priority part identification, and weighting factors. The results of the presented research also indicate that there is significant potential to reduce the environmental impact of product by extending the product lifetime with repair. However, taking into account uncertainties and variabilities related to failure modes and use behaviour in the environmental assessment of repair activities is important to make informed decisions related to repair and assessing the consequence of extending the lifetime of products Forth, the results of the presented research demonstrate the relevance of different allocation procedures when integrating recycling into an LCA. Although, in theory, an EoL approach is more appropriate for a product system delivering high quality recycled feedstock, and a waste mining approach is more suitable for a product system using low grade recycled material, in practice, it is left to the LCA practitioner to decide, often resulting in assumed credits and forgotten burdens. From a circular economy perspective, that envisions quality preservation, the burden of shared processes can be evenly distributed between the first and second use while taking into to account the material losses during recycling and the limitations in terms of tolerable recycled content for the next application. If the quality of the material deteriorates during recycling and evenly distributing the environmental burden associated with material use over the subsequent lifecycle is not appropriate, the allocation should be based on a quality correction factor rather than these potentially avoided processes.

Jaar van publicatie:2021

Toegankelijkheid:Closed