This paper investigates the optimal design of emission control areas (ECAs) for shipping, focusing on minimizing sulfur emissions. The study proposes a mathematical programming model from the regulator's perspective to optimize ECA width and sulfur limits, while also incorporating a model from the shipping liner's perspective to maximize profit by determining detoured voyages, sailing speeds, and cargo transport volumes. A tailored hybrid algorithm based on variable neighborhood search is developed to solve these models. The effectiveness of the proposed methodology is validated through extensive numerical experiments and sensitivity analyses, showing that the optimal ECA design can reduce sulfur emissions by an additional 5% compared to homogeneous ECA designs. The study extends the methodology to heterogeneous ECA settings, where sulfur limits vary across different regions, allowing for more flexible and effective ECA designs. The results suggest that moving the ECA boundary inward and lowering the sulfur limit can lead to significant reductions in sulfur emissions. The study also highlights the importance of considering the interaction between ECA regulations and shipping operations, as stricter regulations may inadvertently increase sulfur emissions due to detour behaviors and changes in transportation modes. The proposed models and algorithms provide a framework for regulators to make informed decisions on ECA design, balancing environmental goals with economic considerations.This paper investigates the optimal design of emission control areas (ECAs) for shipping, focusing on minimizing sulfur emissions. The study proposes a mathematical programming model from the regulator's perspective to optimize ECA width and sulfur limits, while also incorporating a model from the shipping liner's perspective to maximize profit by determining detoured voyages, sailing speeds, and cargo transport volumes. A tailored hybrid algorithm based on variable neighborhood search is developed to solve these models. The effectiveness of the proposed methodology is validated through extensive numerical experiments and sensitivity analyses, showing that the optimal ECA design can reduce sulfur emissions by an additional 5% compared to homogeneous ECA designs. The study extends the methodology to heterogeneous ECA settings, where sulfur limits vary across different regions, allowing for more flexible and effective ECA designs. The results suggest that moving the ECA boundary inward and lowering the sulfur limit can lead to significant reductions in sulfur emissions. The study also highlights the importance of considering the interaction between ECA regulations and shipping operations, as stricter regulations may inadvertently increase sulfur emissions due to detour behaviors and changes in transportation modes. The proposed models and algorithms provide a framework for regulators to make informed decisions on ECA design, balancing environmental goals with economic considerations.