Sustainability assessment of circular economy over time: Modelling of finite and variable loops & impact distribution among related products
T. Schaubroeck, T. Gibon, E. Igos, and E. Benetto
Resources, Conservation and Recycling, doi:10.1016/j.resconrec.2020.105319, art. no. 105319, 2020
To evaluate the sustainability of any economic system, the impact of related products and processes should be considered, which is exactly the aim of life cycle sustainability assessment (LCSA). A first challenge for the current LCSA methodology of circular economy systems, is the consideration of finite and variable loops (e.g. paper fibres can commonly only be recycled a few times). Second, because impact is time-dependant (e.g. financial flows are valued less in the future), loops should be propagated over time. Therefore, we bring forward a general iterative modelling approach (process-by-process) in which flows are tracked over time. A third challenge remains on how to potentially distribute impacts among related products. We present an overview of various approaches, their implications for finite variable loops, whether databases are existing and in which context they should be applied (e.g. for attributional or consequential thinking). A general six-step framework is provided to guide the practitioner. To illustrate this, we developed a simplistic tool (FLOREC BASIC) and performed two case studies. A fictional case on profit generation for flooring reuse, showcases that when considering discounting (10%), producer profit drops about a third. For a case on linerboard recycling, the water scarcity impact is 11% higher for 5 times recycling instead of infinite times. However, when considering the consequential effect on the market, effects are the opposite; linerboard recycling has a higher water scarcity impact, because of its considerable water consumption, compared to incineration with displacement of alternative energy sources that have high water scarcity impact.