Column: Incentivize clean-energy cruise ships The Earth Day 2026 theme, “Our Power, Our Planet,” focused on clean energy, the climate and sustainability. The average ocean-going cruise ship is about 1,000 feet long, weighs 120,000 gross tons and its carbon footprint is significant. Cruise ships, especially those using heavy fuel oil, release significant amounts of carbon dioxide (CO2) per passenger per mile, often more than four times the amount released by air travel.