Marine Diesel Engines and Air Pollution

Do Ships Cause Air Pollution?

The term “preventing air pollution" has lately become an absolute put-off for everyone. In spite of taking several measures against reducing air pollution, industries of all types have been contributing to it in some form or the other. There hasn’t been any type of substantial effort made to alleviate the problem. Moreover, the steps taken are helping in a very minuscule ways when compared to the rising air pollution levels. So why don’t we see any solid progress? “Air pollution” is sometimes like “once the damage is done, it’s done.” This means that we cannot mitigate the amount of pollution already in the air, but can always take precautions to prevent air pollution from proliferating in the future.

However, the problem is much deeper when it comes to air pollution caused by marine vehicles. The worst part about air pollution caused by the marine industry is that nothing drastically can be done about it except making the marine engines cleaner. For now, let’s try to trace the factors of marine diesel engines that result into air pollution, the makers behind marine air pollution, and why marine air pollution is considered the dirtiest of them all.

Marine air pollution – why so bad?

It is an indisputable fact that marine diesel engines contribute significantly to air pollution that damages the environment as well as harms public health. The main reason for marine engines propagating significant air pollution is because they burn the lowest grade of diesel fuel. Diesel engines are used widely as power sources primarily due to their high thermal efficiency, high fuel economy, and durable performance. However, in the process they emit large quantity of toxic gases and solid substances which significantly pollute air.


Image Credits : Cargo Ship polluting the air from cleantechlawandbusiness (

What are these toxic solids and harmful gases?

The marine diesel engine’s toxic emissions mainly consists of the following components

  • Smog
  • Particulate matter
  • Global warming gases

Smog – forming emissions

Nitrogen oxide (NOx)

NOx is formed when nitrogen combines with oxygen inside the extremely hot and highly pressurized chambers of marine diesel engines. This NOx combines with hydro carbons in the atmosphere forming ozone which produces smog. Ozone is good when it is high in the stratosphere, where it protects earth from the ultraviolet rays of the sun, but when ozone is dangerously low in the atmosphere it traps heat and badly affects human health.

Sulfur dioxide (SOx)

SOx is formed when unburned fuel in diesel engines produces small particles of sulfur and carbon, which together contribute to smog. SOx is directly related to the sulfur content in fuel, which when combined with water vapor, results in acid rain.

Chloroflorocarbons (CFC’s)

Emissions of CFCs from the global shipping fleet is estimated at 3,000-6,000 tons or approximately 1 to 3 percent of yearly global emissions. CFCs are also extremely poisonous as far as air pollution is concerned.

Particulate matter

Particulate matter consists of tiny solid particles and liquid droplets which consist of soot, dust, salt, acid, and metals that are invisible to the human eye but that appear as a cloud or fog. These particles are less than 10 microns in diameter and one seventh the thickness of human hair. Diesel contains 60 to 200 times more small particles than those in gasoline engine exhaust.

Global Warming gases

Gobal warming gases includes methane, nitrogen oxide and the cruelest culprit – carbon dioxide. All these are produced from the burning of fossil fuels. These gases when in atmosphere trap heat and cause global warming and climate change. It has been predicted that global warming will lead to dilapidated environmental concerns in the near future if adequate steps to reduce emission of toxic gases is not taken.

To find out about the regulations and steps that needs to be taken in order to reduce emissions from marine diesel engines read cold ironing techniques.


Marine diesel engines and air pollution : Blue water networks