Cargo ships are responsible for the movement of about 90% of the world’s freight, but because most of them run on low-grade diesel fuel, they do output quite a bit of carbon pollution. David R. Cocker III and his team discovered that because ships burn fuel on an exponential basis, running a ship at half its speed would reduce its exhaust output by much more than half.
They found that on average, a ship traveling at 14 mph versus running at 25-29 mph led to a reduction in carbon dioxide, nitrogen oxides, and soot emissions by 60%, 55%, and 70% respectively. Now multiply those figures by the 100,000+ cargo ships making their way across various channels of water on a daily basis and you can imagine the massive reductions in air pollution.
While operating a ship at half speed for its entire journey has its cons, the researchers suggested that countries impose speed restrictions near coastal regions and ports for the sake of people living in those areas.
You can read up more about this in ACS’ journal ‘Environmental Science & Technology’.