Industrial symbiosis (IS) involves transferring waste materials and/or energy flows between stakeholders to enhance resource efficiency and reduce environmental impacts. The success of these transactions depends on supply–demand matching, technical feasibility of waste integration into industrial processes, economic savings, and compliance with legal and environmental regulations. This paper presents a methodology for the technoeconomic assessment of IS projects, integrating material flow cost accounting (MFCA) and cost–benefit analysis (CBA) incorporating CAPEX and OPEX considerations. MFCA, traditionally used to identify hidden costs from inefficiencies, is adapted here to assess resource utilisation across industry networks. The methodology is applied to two real-world demo cases: a novel fertiliser production process in Escombreras (Spain), where IS focuses on process optimisation and by-product valorisation, and an IS process design in Frövi (Sweden), where CO₂ and residual energy flows are exchanged between industrial sectors. The results demonstrate the potential of MFCA-CBA integration to enhance decision making in IS implementation. In Spain, process optimisation led to a 50% reduction in operating costs, whereas, in Sweden, CO₂ reutilisation resulted in a 30% increase in resource efficiency. These findings highlight the economic and environmental benefits of IS and provide insights into cost allocation and pricing strategies.

Parabolic trough concentrated solar power (CSP) plants are particularly promising renewable sources of energy, whose easy integration with thermal energy storage (TES) systems allows to mitigate the intermittency of electricity generation. Currently, molten nitrates, with two tanks arrangement, are mainly used for sensible heat accumulation. To reduce costs and make the CSP storage systems more manageable, single tank configurations have been proposed, where the cold and hot fluids are stored in the same container and separated because of their density difference. The aim of the present work is to study the storage performances presented by two novel ternary and quaternary mixtures, proposed within the European project IN POWER. An experimental campaign was preliminarily performed to investigate the fluids thermo-physical properties, and the obtained values were utilized as input data to model the discharge phase in a thermocline tank. The simulation results were compared with the ones acquired considering two commercial materials, namely, solar salt and Hitec XL®. Overall, considering same temperature ranges, higher discharging times are obtained for the quaternary and ternary mixtures, with the ternary presenting a smaller thermocline thickness than the solar salt while this parameter is the same considering the quaternary and Hitec XL®.

The decarbonization of industrial processes requires efficient and scalable renewable energy solutions. Concentrated Solar Power (CSP) technology stands out by providing both electricity and high-temperature heat, yet its optimal deployment remains a challenge. This study presents an innovative framework for selecting and optimizing CSP technologies tailored for potential industrial practical applications. In this study, a multi-phase approach is deployed integrating a decision matrix, performance simulations using SOLARPILOT and SAM, and techno-economic evaluation to identify the best CSP solution. The study addresses the feasibility of four candidate CSP technologies, the characteristics of deployment areas, operation parameters such as energy storage time, and characteristics of energy storage material (comparing commercially available materials and an innovative molten salt named FERT-1). The results highlight solar towers as the most suitable technology, while the characteristics of the deployment can lead to over 3.2% difference in annual energy generation (when comparing between two areas, A1 and A2). Regarding energy storage, an optimal storage time of 11 h was identified, achieving a Levelized Cost of Electricity (LCOE) of 24–25 cents/kWh and a 31–32% energy capacity factor. Moreover, regarding energy storage material, the innovative molten salt highlighted improved thermal efficiency.

Industrial symbiosis (IS) plays a crucial role in enhancing sustainability within industrial ecosystems by facilitating the exchange of waste, by-products, energy, and resources among different industries. This collaborative approach reduces resource consumption, minimizes waste generation, lowers disposal costs, and creates economic opportunities through synergistic relationships. This study focuses on the production of potassium nitrate (KNO₃) in the Escombreras industrial area in Spain, employing life cycle assessment (LCA) and life cycle cost analysis (LCC) to evaluate the impact of IS strategies. The ReCiPe method, implemented through SimaPro software and supported by market data from the Ecoinvent 3.8 database, is used for a comparative analysis between conventional KNO₃ production and improved technologies that promote circular economy principles. The LCA and LCC methodologies provide a comprehensive evaluation of both environmental and economic performance, considering key factors influenced by IS synergies. Results demonstrate significant environmental and economic benefits from the integration of IS into KNO₃ production, revealing the potential for improved sustainability and competitiveness through circular economy practices. This research provides valuable insights into how IS can enhance both environmental performance and cost-efficiency in industrial processes. These findings support the integration of IS as a viable pathway toward sustainable and cost-effective fertilizer production.