Technical substitutability of recycled materials in life cycle Assessment: A comprehensive review and framework for quantification.

In evaluating environmental sustainability with methodologies like life cycle assessment (LCA), recycling is usually credited for avoiding impacts from virgin material production. Consequently, the LCA results are influenced by the manner in which the substitutability of virgin by recycled materials is estimated. This study reviews how the scientific community assesses the technical substitutability of recycled materials in LCA. Accordingly, 49 peer-reviewed papers were in-depth analysed, considering aspects such as materials studied, type of substitution, recycled material (rMaterial) application, and life cycle stages (LCSs) where substitution was evaluated. The results show that 49% of the papers investigated material substitutability through technical and economic aspects. 51% of the articles did not consider the final application of the rMaterial. Plastics were the most studied material, and mass was the most used property to quantify technical substitutability. Certain materials were more analysed in specific LCSs (e.g., metals in the natural resource extraction stage). As 51% of the papers developed a new approach for substitutability calculation, this shows that substitutability is still a concept in development. It was noticed in 33% of the papers that substitutability values were taken from external sources, and in some cases were used without considering whether they were representative for a specific case. Aspects such as harmonization, transparency, and consideration of the application of recycled materials, therefore, require more attention in substitutability evaluation. Based on the results, a step-wise framework to measure technical substitutability at different LCSs was developed to guide researchers in including substitutability in LCA studies.

The environmental impact of household's water use: A case study in Flanders assessing various water sources, production methods and consumption patterns.

Responsible water use and sustainable consumption and production are high on the agenda of multiple stakeholders. Different water supply sources are available, including tap water, bottled water, domestically harvested rainwater and domestically abstracted groundwater. The extent to which each of these water supply sources is used, differs over consumption patterns in various housing types, being detached houses, semi-detached houses, terraced houses and apartments. To identify the environmental impact of a household's water use and potential environmental impact reduction strategies, a holistic assessment is required. In this paper, the environmental impact of a household's water use in Flanders (Belgium) was assessed including four different water supply sources and four different consumption patterns by means of a life cycle assessment. The outcomes of this study reveal a large difference between the environmental impact of bottled water use, having a global warming impact of 259 kg CO2-eq.·m-3, compared to the other three supply sources. Tap water supply had the lowest global warming impact (0.17 kg CO2-eq.·m-3) and resource footprint (6.51 MJex·m-3) of all water supply sources. The most efficient strategy to reduce the environmental impact of household's water use is to shift the water consumption from bottled to tap water consumption. This would induce a reduction in global warming impact of the water use of an inhabitant in Flanders by on average 80%, saving 0.1 kg CO2-eq.·day-1 in case of groundwater-based tap water. These results provide insights into sustainable water use for multiple consumption patterns and can be used to better frame the environmental benefits of tap water use.

Development and application of a predictive modelling approach for household packaging waste flows in sorting facilities.

Household packaging waste sorting facilities consist of complex networks of processes to separate diverse waste streams. These facilities are a key first step to re-enter materials into the recycling chain. However, so far there are no general methods to predict the performance of such sorting facilities, i.e. how efficiently the heterogeneous packaging waste is sorted into fractions with value for further recycling. In this paper, a model of the material flow in a sorting facility is presented, which allows changing the incoming waste composition, split factors on the sorting units as well as the setup of the sorting facility. The performance of the sorting facility is judged based on the purity of the output material (grade) and the recovery of the input material. A validation of the model was performed via a case study on Belgian post-consumer packaging waste with a selection of typical waste items that can be found in this stream. Moreover, the model was used to predict the possible sorting qualities of future Belgian post-consumer packaging waste after an extension of the allowed waste packaging items in the waste stream. Finally, a sensitivity analysis was performed on the split factors, which are a key data source in the model. Overall, the developed model is flexible and able to predict the performance of packaging waste sorting facilities as well as support waste management and design for recycling decisions, including future design of packaging, to ensure proper sorting and separation.

Circular economy indicators: What do they measure?

Circular Economy (CE) is a growing topic, especially in the European Union, that promotes the responsible and cyclical use of resources possibly contributing to sustainable development. CE is an umbrella concept incorporating different meanings. Despite the unclear concept, CE is turned into defined action plans supported by specific indicators. To understand what indicators used in CE measure specifically, we propose a classification framework to categorise indicators according to reasoning on what (CE strategies) and how (measurement scope). Despite different types, CE strategies can be grouped according to their attempt to preserve functions, products, components, materials, or embodied energy; additionally, indicators can measure the linear economy as a reference scenario. The measurement scope shows how indicators account for technological cycles with or without a Life Cycle Thinking (LCT) approach; or their effects on environmental, social, or economic dimensions. To illustrate the classification framework, we selected quantitative micro scale indicators from literature and macro scale indicators from the European Union 'CE monitoring framework'. The framework illustration shows that most of the indicators focus on the preservation of materials, with strategies such as recycling. However, micro scale indicators can also focus on other CE strategies considering LCT approach, while the European indicators mostly account for materials often without taking LCT into account. Furthermore, none of the available indicators can assess the preservation of functions instead of products, with strategies such as sharing platforms, schemes for product redundancy, or multifunctionality. Finally, the framework illustration suggests that a set of indicators should be used to assess CE instead of a single indicator.