Epsilon Archive for Student Projects

Abstract

Circular Economy (CE) and Circular Nutrient Economy (CNE) have garnered increasing atten-tion in both public discourse and scientific research over the past decades. The fundamental principle of CNE is to transition away from linear organic material flows by maximizing recycling and reuse while minimizing the reliance on virgin resource inputs and the disposal of unrecoverable organic waste. At the regional level, various indicators and methodologies have been developed to assess the extent to which CNE objectives are achieved, although there is yet no standardized set of indicators and neither consolidated agreement on what CNE objectives entail.

The primary aim of this study was summarizing existing literature on CNE concepts and Circu-larity Indicators (CIs) relevant to CNE mass flows at the regional scale. Secondly, this research sought to synthesize and operationalize CNE concepts by developing a novel framework that incorporates key CNE objectives. Lastly, the study applied newly developed indicators to assess the CNE performance of four regional systems in Europe, facilitating a comparative analysis of the actual state of CNE objectives and their circularity performance.

Despite the broad range of CNE goals identified in the literature, this study delineates three cri-teria for regional CNE objectives: (1) 4R framework, (2) the soil potential and biomass production limits of the region, (3) toxicity and regeneration at all system stages. The Phosphorus Output Circularity Index (POCindex) assesses criterium 1, ranking into classes the CNE benefits of the regions from A (high) to D (insufficient). Applied to Mass Flow Analysis (MFA) of Branden-burg, Denmark, Brussels-Capital, and Switzerland, all regions scored C, indicating rather low CNE performances. Criterium 2 was assessed via the Standard Livestock Unit deviation (SLUdev), re-vealing reliance on imported feed and insufficient marginal land for self-sufficiency in all four regions. Criterium 3 was evaluated by applying the share of organic phosphorus (P) inputs, which remained low (~10%), raising concerns about organic material safety.

The POCindex, the organic P input share, and the SLUdev indicators rely on broad assumptions, literature-derived data, and simplified mathematical formulations. While these indicators provide new qualitative insights and facilitate assessments based on readily available mass flow data, their scientific robustness remains limited and other objectives of CNE, such as import dependen-cy, crop production, food waste reduction & reuse, or environmental impact, remain unaddressed. A key challenge identified in this study is the multidimensional nature of CNE concepts, which encompasses social, economic, global, and environmental dimensions. Future research should focus on identifying the most effective metrics and standardizing CNE evaluation methodologies to enhance the reliability and comparability of regional circularity assessments.