Novel circularity and sustainability assessment of symbiosis networks through the Energy Quality Pinch concept

Circular Economy is a well-known concept to mitigate global resource depletion issues. The sustainability of a system is closely related to its environmental performance, which is directly linked to energy consumption. This work provides a circularity assessment tool by determining the minimum system energy requirements, according to the Energy Quality Factor, as it indicates the useful energy that can be extracted from material and energy flows. The proposed tool is Energy Quality Pinch Analysis which identifies the minimum energy requirements for a circular system and shows the system's sustainability. The analysis considers cascades of the energy used and released by recycling and symbiosis processes, evaluating the minimal external energy flows: high-quality energy input and waste energy output. The method is applied to case studies, including Total Site Heat and Power Integration, chemical energy reuse in wastewater systems, and Municipal Solid Waste management. Practical energy conversion technologies in each study are proposed as well. The results of the case studies indicate that the degree of energy recovery rate can be as high as 60% for the case of the utility system and higher for the cases of wastewater and municipal waste treatment, providing potentially valuable guidance to system designers.