Circular economy has gained attention as a key solution for mitigating the increasing generation of solid waste and resource scarcity. As opposed to the linear economy, the concept describes how to develop closed-loop technical and biological cycles by either recycling materials indefinitely with no degradation of their properties (the technical cycle) or returning materials to the natural ecosystem with no harm to the environment (the biological cycle) . Although circular economy practices (such as material recycling) are widely embraced as a sustainability strategy, it is important to consistently assess their net environmental benefits and possible drawbacks  and develop methods and indicators that are suitable for assessing circular economy concepts . The term “circular economy” is frequently applied to suggest increased sustainability. However, it tends to focus on an increased quantity of reused and recycled resources and overlook the quality of resource flows re-entering to the product cycle . This can pose a risk of augmenting unwanted recirculation of micro-pollutants [5,6,7,8], if disregarding the material quality, particularly in the transition period from linear to circular systems. In 2015, 241 million tonnes of municipal solid waste were generated in the EU . Of this waste, 40–60% was organic waste , representing a great challenge in terms of its management. However, at the same time, organic waste also constitutes a valuable resource as a component in the circular bioeconomy [11,12]. Biowaste-based biorefineries, producing high value products such as enzymes, bioplastic and biofertilizer from the organic fraction of municipal solid waste, is an emerging technology field whose environmental performance should be addressed to ensure a beneficial implementation . This study refers to such circular economy systems related to management of municipal biowaste as circular biowaste management systems (CBWMS). Several decision support tools (DSTs) based on life cycle assessment (LCA) are currently available to assess the sustainability of waste management systems (WMS). These WMS-DSTs are specifically developed to analyse the performance of integrated WMSs from collection, treatment and final disposal. Winkler and Bilitewski  and Jain et al.  showed large discrepancies in the results obtained when modelling specific scenarios across different WMS-DSTs. Gentil et al.  analysed the technical assumptions that caused the difference in the results obtained with various WMS-DST; e.g., time horizon for landfill emissions and calculation of long-term carbon balance when applying biowaste derived compost on soil .
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