Assessing the sustainability of urban eco-systems through Emergy-based circular economy indicators

Circular Economy (CE) concepts and tools are getting increasing attention with regard to their implementation in agricultural, urban and industrial sectors towards innovative business models to optimize resource use, process performances and development policies. However, conventional biophysical and economic indicators hardly fit CE characteristics. Life cycle assessment, footprint and economic cost-benefit indicators, do not fully capture the specificity of a closed loop CE framework, characterized by feedbacks and resource use minimization and quality assessment Commonly used mono-dimensional indicators seem unable to successfully relate the process performance and the use of ecosystem services and natural capital, in that they do not assess the environmental quality and sustainability (renewability, fit to use, recycle potential) of resources and the complexity of interaction between agro/industrial/urban environments and socioeconomic systems, and translate into an incomplete and inadequate picture, far from an effective CE perspective. In this study, Emergy Accounting method (EMA) is used to design an improved approach to CE systemic aspects, focusing on the importance of new indicators capable of capturing both resource generation (upstream), product (downstream) and systems dimensions. This conceptual scheme is built around the case study of the City of Napoli's economy (Campania region, Southern Italy) considering the surrounding agro-industrial area with its smaller urban settlements. In order to design a reasonable and reliable CE framework, a number of already existing and innovative processes is analyzed and discussed, through a bottom-up procedure capable to account for CE development options based on the recovery of locally available and still usable resources (i.e., conversion of waste cooking oil into biodiesel, conversion of slaughterhouse residues to power and chemicals, recovery and conversion of agro-waste residues, amongst others). The result highlighted that EMA was capable to keep track of the improvement generated by the implemented circularity patterns in terms of reduced total emergy of the system. Moreover, EMA indicators suggested that, in any case, the CE business framework should be intended as a transitional strategy towards more feasible paradigms.