In this paper, unit commitment is solved for superconducting magnetic energy storage (SMES) based thermal system to study effect on environmental pollution and operating cost. A modified Lagrange Relaxation based Henry gas solubility optimization (LR-HGSO) is proposed with an objective of minimizing the emission and operating cost for solving unit commitment in IEEE 10-unit 24-hour system in two case studies. In the first case study, SMES based thermal system with emission constraint is considered for solving unit commitment. The amount of emission as well as operating cost of dispatch units is calculated and compared for thermal system with and without SMES to show the SMES impact on emission in the environment. In the second case study, different sizing of SMES is considered and integrated with thermal system, to identify the optimal sizing of SMES. In both test cases, the results of LR-HGSO are compared to other conventional methods and found the operating cost of LR-HGSO as well as emission is low. © 2020 Elsevier Ltd