Seaports significantly contribute to global greenhouse gas emissions, accounting for 2.89% of global CO2 emissions. Despite previous efforts to mitigate their environmental impact, these have largely been ineffective. Currently, seaports are turning towards decarbonization projects through renewable energy sources. However, implementing renewable energy in ports presents several challenges, and research on the environmental impacts of these systems is limited. This paper assesses the environmental impacts of renewable energy systems in seaports using contemporary methodologies such as Conensa and Delphi. The study evaluates 26 seaports that have adopted solar, wind, tidal, and wave energy technologies to analyze their environmental impacts. The findings reveal that a combination of all four renewable energy sources leads to the highest environmental impacts. Conversely, tidal and wave energy emerge as the most effective options for decarbonizing ports while minimizing environmental harm. The study also identifies key policies to support renewable energy implementation in seaports, including tax incentives, subsidies, prioritization of wave and tidal energy, regulation of solar energy, and the development of technologies suited to local ecosystems. These measures are essential for reducing the environmental footprint of seaports while promoting sustainable energy practices.