The emission crisis in the iron and steel sector prompted the search for modern systems that contribute to reducing the resulting emissions to alleviate the growing concerns about global warming. This research evaluates four flue gas treatment systems in the iron and steel sector through a case study in Egypt. A comprehensive approach is presented through which experts can use linguistic terms and their corresponding spherical fuzzy numbers (SFNs) to express their views on identifying aspects and indicators that affect the sustainability of flue gas treatment systems. Also, determining the optimal system for dealing with emissions is a necessary task, which requires consideration of many aspects of sustainability, including economic, environmental, and technological aspects and their subindicators. This paper presents a new hybrid approach to multicriteria decision-making (MCDM) under a spherical fuzzy (SF) environment that takes into account several incompatible indicators. The SF-CRiteria Importance through Intercriteria Correlation (SF-CRITIC) has been used to assess and prioritize the main aspects and subindicators. The SF-COmbinative Distance-based ASsessment (SF-CODAS) has been applied to evaluate and rank the selected systems. A sensitivity analysis has been implemented to confirm the effectiveness of the recommended hybrid approach and the stability of its results by changing the weights of the indicators used. Also, a comparative analysis has been fulfilled with MARCOS and WASPAS methods under an SF environment to validate the proposed approach. The findings show that the environmental aspect is the highest evaluated with a weight of 0.431, followed by the technological aspect with a weight of 0.326, and they are the basis for enhancing the sustainability of low-emission systems in the iron and steel sector. Furthermore, the conclusions advise optimizing low-emission systems for sintering flue gas in the iron and steel sector to improve sustainability.