Metrics for optimising the multi-dimensional value of resources recovered from waste in a circular economy: A critical review

© 2017 The Authors - Established assessment methods focusing on resource recovery from waste within a circular economy context consider few or even a single domain/s of value, i.e. environmental, economic, social and technical domains. This partial approach often delivers misleading messages for policy- and decision-makers. It fails to accurately represent systems complexity, and obscures impacts, trade-offs and problem shifting that resource recovery processes or systems intended to promote circular economy may cause. Here, we challenge such partial approaches by critically reviewing the existing suite of environmental, economic, social and technical metrics that have been regularly observed and used in waste management and resource recovery systems' assessment studies, upstream and downstream of the point where waste is generated. We assess the potential of those metrics to evaluate ‘complex value’ of materials, components and products, i.e., the holistic sum of their environmental, economic, social and technical benefits and impacts across the system. Findings suggest that the way resource recovery systems are assessed and evaluated require simplicity, yet must retain a suitable minimum level of detail across all domains of value, which is pivotal for enabling sound decision-making processes. Criteria for defining a suitable set of metrics for assessing resource recovery from waste require them to be simple, transparent and easy to measure, and be both system- and stakeholder-specific. Future developments must focus on providing a framework for the selection of metrics that accurately describe (or at least reliably proxy for) benefits and impacts across all domains of value, enabling effective and transparent analysis of resource recovery form waste in circular economy systems.We gratefully acknowledge support of the UK Natural Environ-ment Research Council (NERC) and the UK Economic and SocialResearch Council (ESRC) who funded this work in the context of‘Complex Value Optimisation for Resource Recovery’(CVORR)project (Grant No. NE/L014149/1)

Influence of calcium carbonate on RTM and RTM light processing and properties of molded composites

In the RTM light composite manufacturing process, inorganic fillers are commonly added to the resin to reduce cost and alter the final composite properties, especially rigidity, even though they also adversely affect processability. The aim of this study is to evaluate resin characteristics, reinforcement permeability, and mechanical properties of the composite and analyze the detrimental effects when a variable amount of calcium carbonate (CaCO3) is added to the resin. The addition of calcium carbonate increased the viscosity and gel time of the resin and considerably decreased the permeability of the reinforcement and therefore the expected process productivity. Besides, Barcol hardness, short-beam strength, and elastic modulus increased for higher CaCO3 content, whereas Izod impact, flexural, and tensile strengths decreased. Besides, the coarser CaCO3 filler particles managed to penetrate only partially into the fiber-rich layer of the combination mat used, which comprised of a PP flow media core and glass fibers at the surface

A new approach for preparation of metal-containing polyamide/carbon textile laminate composites with tunable electrical conductivity

Multiscale thermoplastic laminate composites based on polyamide 6 (PA6) dually reinforced by carbon fiber woven textile structures (CFT) and different micron-sized metal particles are prepared for the first time by microencapsulation strategy. In a first step, activated anionic ring-opening polymerization (AAROP) of epsilon-caprolactam is carried out in suspension, in the presence of different metal particles, to produce shell-core PA6 microcapsules (PAMC) loaded with 13-19% metal. In a second step, the loaded PAMC are distributed between CFT plies with fiber volume fractions V (f) = 0.25 or V (f) = 0.50 and then the ply arrays are consolidated by compression molding. Separately, metal-loaded PA6 hybrid composites are prepared by direct compression molding of PAMC and used to compare their properties to the CFT-metal laminates. Light- and scanning electron microscopy are used to study the morphology and the interfaces between the fillers and the polymeric matrix. These structural results are related to the mechanical behavior in tension and the electrical properties. A notable increase of the d.c. electrical conductivity in 7 orders of magnitude is observed for the CFT-metal laminates with respect to the neat PA6. This increase is accompanied by a 2.5-3.0 times growth of the Young's modulus and of the strength at break. It is concluded that the microencapsulation strategy can be applied to produce multifunctional CFT-metal-PA6 thermoplastic composites with tailored electrical and improved mechanical properties for advanced applications.The authors gratefully acknowledge the financial support of the project TSSiPRO NORTE-01-0145-FEDER-000015, supported by the regional operation program NORTE2020, under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund, as well as funding from FCT-Portuguese Foundation for Science and Technology within the strategic projects UID/CTM/50025/2013, LA25/2013-2014 and UID/FIS/04650/2013. FMO acknowledges also the PhD grant PD/BD/114372/2016 of FCT-Portugal (AdvaMTech-PhD Program in Advanced Materials and Processing) and PM the FCT SFRH/BPD/96227/2013 grant. Finally, ZZD is thankful to FCT for the SFRH/BSAB/130271/2017 personal research grant. Finally, SLM acknowledges funding from the Basque Government Industry Department under the ELKARTEK program.info:eu-repo/semantics/publishedVersio