Shipping already accounts for roughly 80 percent of the kilometers required for freight transportation and leisure cruises are also increasing in popularity. According to the UN, ships are amongst the most important CO₂ emitters. The Emma Mærsk, one of the largest container ships worldwide, produces as much CO₂ on her yearly journeys from China to Europe as a mid-sized coal-fired power plant. 90 percent of ships are still fueled by heavy fuel oils, whose high sulfur content leads to very high SO₂ emissions. All this confirms that urgent action needs to be taken.