A quadruple optimization framework for cost-effective decarbonization of Saudi Arabia's steel industry via green hydrogen integration

Decarbonizing energy-intensive industries is essential for meeting global climate goals, particularly in fossil fuel-reliant economies such as Saudi Arabia. The steel sector, one of the country's largest industrial emitters, presents a critical opportunity for deep emissions reduction by integrating green hydrogen energy systems. In response, this study develops a comprehensive planning and optimization framework that supports steel production's economical and sustainable transition toward hydrogen-based electrification. A quadruple optimization framework is proposed to evaluate green hydrogen energy systems’ performance across four sustainability pillars: economic cost, energy reliability, environmental impact, and employment generation. The system architecture comprises photovoltaic, wind turbines, electrolyzer, hydrogen storage tanks, fuel cells, boilers, and grid interaction. A hierarchical optimization strategy is adopted, in which total net present cost serves as the primary objective function, while additional performance indicators, including levelized cost of hydrogen, greenhouse gas emissions, capacity shortage fraction, unmet demand, payback period, internal rate of return, and job creation, are evaluated through post-optimization trade-off analysis. A real-world steelmaking facility in Al-Jubail, Saudi Arabia, is used as a case-study. The optimal configuration yields a total net present cost of $33.86 M, and a levelized cost of hydrogen of $4.72/kg, while achieving a 95.13 % reduction in greenhouse gas emissions. Employment impacts are assessed using a capacity-weighted employment estimation method and a task-based employment model, with the latter estimating 95 jobs for the optimal system. A sensitivity analysis reveals that anticipated improvements in electrolyzer efficiency and cost reductions in solar and wind technologies could further decrease the cost of hydrogen to $3.46/kg and the total net present cost by over 25 %, demonstrating the economic robustness of green hydrogen energy systems under future market conditions. These results demonstrate the technical, economic, and policy viability of such systems integration for industrial decarbonization and underscore the value of multi-criteria energy system design in supporting Saudi Arabia's long-term sustainability objectives under Vision 2030.