The Shipping Industry’s Contribution: Global Warming and Air Pollution
About how the shipping industry contributes to global warming and air pollution through specific fuel consumption and other factors. This article focuses on bigger vessels.
Right now I’m sitting at my desk that I bought from the internet. Various journals and stationery surround me from Amazon. I just took a sip of water from a water bottle I got at Target. The bed behind me is from IKEA. None of these things have a clean trail behind them, they were all, at least partially, shipped from different countries. Around 90% of the world’s trade is transported by sea by approximately 90,000 ships.
Just look at this live map!
However, the negative side effects that come from this industry are almost as big as the industry itself.
This article will go into the details of how the shipping industry contributes to global warming through fuel consumption and a few other factors.
Contents
Overview
Greenhouse Gas Emissions
Atmospheric Pollutants
Alternatives
Conclusion
Overview
As I mentioned before, ships are quite constantly shipping cargo from point A to point B. This means that ships consistently require large amounts of fuel. When someone needs to buy a stable supply of something, they look at the price and efficiency of different products, looking for the “bang for the buck” deal. The majority of the shipping industry finds this deal in the inexpensive yet energy efficient Heavy Fuel Oil.
Heavy Fuel Oil, or HFO, is so inexpensive because it’s actually a type of “leftover oil” from processes of mining petroleum and the crude oil refining process. It is around 30% cheaper than the alternatives. Not only is it widespread and cheap, but it’s also high in energy.
Heavy fuel oil is, as you may have guessed, heavy. This is because the oil has many long carbon chains which make it very dense. Longer carbon chains mean more energy is produced during combustion since there are more bond energies that need to break apart to produce a larger amount of energy.
This CO2 emission process is what leads us to consider the various downsides of heavy fuel oil as a fuel source.
Greenhouse Gas Emissions
To better understand how the shipping industry contributes to greenhouse gas emissions, we need to understand how the process of combustion works.
A ship uses fuel for energy through the aforementioned process of combustion. The fuel is pressurized with air inside an engine cylinder until they’re compressed so much that the mixture explodes and creates heat. This heat in turn puts more pressure on the burning gas and causes the pistons attached to the cylinder to move and affect the movement of a propeller. During the process of combustion, carbon from the fuel and oxygen from the air combine to create carbon dioxide, the well-known greenhouse gas that contributes to climate change. The used-up gas is drawn out through an exhaust pipe, and fresh air replaces it for the next combustion reaction. This process is repeated for as long as energy is needed. For a more thorough explanation, read this article. Nearly all of the fuel carbon (99 percent) in fuel oil is converted to CO2 during the combustion process.
CO2 emissions are no doubt one of the main causes of global warming. The shipping industry produces 1 billion metric tons of CO2 annually. This accounts for 3% of all greenhouse gas emissions. With these numbers, the shipping industry might seem like it doesn’t contribute to global warming as much as compared to other contributors like the energy or car industries, but a change in perspective proves else wise.
Air Pollutants
According to multiple articles, including one from the World Economic Forum, “The shipping industry is the sixth most significant greenhouse gas emitter worldwide, ranking between Japan and Germany. These greenhouse gases include Carbon Dioxide, Black Carbon, and Nitrogen Oxide.”
While this is true, it’s also false. Carbon dioxide is the only main greenhouse gas that the shipping industry produces. Black carbon and Nitrogen Oxide are what are known as “air pollutants”. Aside from the misnomers, the article forgot to mention Sulfur Dioxide — another prominent air pollutant.
Air pollutants are substances that pollute the air in concentrated quantities. Different types of air pollutants have different effects. The ones that the shipping industry mainly produce have especially negative effects on the environment and human health.
Black Carbon: This is a type of fine particulate matter that results from the poor or incomplete combustion of fuel. The particularly dark color allows it to absorb a lot of heat when emitted. In fact, it’s the strongest light-absorbing component of particulate matter. Black carbon is also a short-lived pollutant, which means that it falls out of the sky after a few days, warming up the Earth with all the solar radiation it absorbed. This is especially frightening when we consider the scale of this pollutant: “Black carbon from all sources is the second largest contributor, after CO2, to human induced climate change” (Bond et al., 2013). Currently, there are no regulations controlling black carbon emissions from shipping.
Sulfur Dioxide: As mentioned previously, HFO is a type of leftover oil from crude oil mining and petroleum processes. This means that they often contain heavy metal impurities and are usually high in sulfur, with an average content around 2.5% by weight, equivalent to 25,000 parts per million (ppm). When is consumed through combustion, the sulfur and oxygen create Sulfur Dioxide, a gaseous air pollutant. This pollutant is so dangerous because in the atmosphere it can turn into sulfates, a major part of fine particle pollution in the U.S, or it mixes with water and air to create the main component of acid rain, sulfuric acid. Aside from these already detrimental issues, sulfer dioxide can also cause a variety of respiratory diseases and problems to those who are exposed to it. Thankfully, there have been a handful of initiatives and governmental limits/bans in place to cap the amount of sulfur that can be in the oil a ship is using. There are also new processes and innovations that help reduce the amount of sulfur in heavy fuel oil. Read this for more information about this.
Nitrogen Oxide: The air we breathe is a mixture of around 78% nitrogen and 21% oxygen. The air we breathe is also the air a ship uses to bring oxygen into the processes of combustion. When the nitrogen from the air forcefully merges with oxygen atoms during combustion, it creates nitric oxide (NO). This further combines with oxygen to create nitrogen dioxide (NO2). Together, these are known as oxides of nitrogen (NOx). NOx causes quite a few different issues. First of all, it actually contributes to the chemical reactions that create ozone. Secondly, just like with sulfur dioxide, it can lead to the formation of acid rain. Thirdly, it is poisonous and highly reactive. When inhaled, it can cause converts into nitrous and nitric acid, which are highly irritating and cause damage to lungs. An exposure of 0.06–0.1 ppm of N02 for two years causes acute respiratory disease. Aside from these issues, high levels of nitrogen dioxide are also harmful to vegetation — damaging foliage, decreasing growth or reducing crop yields. The scale is of concern here as well because shipping accounts for 18% — 30% of global nitrogen oxide emissions. Because of all of this, it is one of six widespread air pollutants that have national air quality standards to limit them in the outdoor air. While limits have been made in certain countries about how fast ships can go to try and mitigate how much NOx forms, there aren’t many successful or currently implementable innovations to solve this.
Alternatives
Most alternative fuels are either less energy dense, more expensive, or both. Even small negative changes in either one of these variables multiplies into big differences simply because of the size of the shipping industry. Since lots of fuel is constantly being purchased and consumed, small changes in energy density and/or price matter a lot.
Some of the most well-known alternatives are:
Marine Diesel Oil (MDO): More energy dense & more expensive.
Lighter Marine Gas Oil (MGO): Less energy dense & more expensive. No economical benefit here.
Oleochemical Biofuel (HVO): More energy dense & way more expensive. Hard to implement into existing engines, not compatible with current marine diesels. No economical benefit here.
Liquid Natural Gas (LNG): Much less energy dense. While in general it may be better for the environment, the energy required to chill, ship, and regasify the fossil fuel makes it far more carbon-intensive and increases the potential for leakage of dangerous methane. No benefit here.
While lighter marine gas oil and marine diesel oil fuels are more energy dense, they are also significantly more expensive than heavy fuel oil (HFO), so commercial shipping still uses heavy fuel oil for the most part.
Conclusion
To summarize, the shipping industry is responsible for transporting around 90% of the worlds trade. Most ships, especially the ones that often go long distances, use Heavy Fuel Oil. They prefer this type of leftover fuel because of how inexpensive, yet energy dense it is compared to other types of fuel. This is a detrimental issue. Heavy Fuel Oil emits carbon dioxide, black carbon, sulfur dioxide, and nitrogen dioxide.
I think that the issue of black carbon emissions needs to be addresses first and foremost since it has debilitating effects on the climate — an issue that needs solving ASAP. I plan to look into how to reduce the amount of black carbon being produced by the shipping industry by digging into exactly why fuel is being poorly or incompletely combusted. The sulfur and nitrogen emissions have solutions being implemented to limit them, either in the form of limits, bans, and/or innovations. However, I did not find many to stop black carbon, despite it being one of the biggest contributions from this industry.
This article will have an extension article talking about the how the shipping industry contributes to ocean acidification through sulphur pollution —a topic that I am very passionate about.
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