Brian Barton
Container ships are a major source of pollution, contributing significantly to global greenhouse gas emissions. The shipping industry accounts for about 3% of global greenhouse gas emissions, comparable to the total emissions from aviation. The largest container ships burn an estimated 66 gallons of fuel per minute while in transit, and the fuel used often contains high levels of sulphur, leading to the emission of sulphur oxides and other harmful pollutants. In addition to air pollution, container ships also contribute to water pollution through ballast water discharge, biocides, waste disposal, and oil spills. While some companies are exploring alternative fuels and technologies to reduce emissions, the high demand for shipping poses a significant challenge for mitigating the industry's environmental impact.
| Characteristics | Values |
|---|---|
| Container ships' contribution to global greenhouse gas emissions | 3% |
| Container ships' ranking as a contributor to climate change if they were a country | 6th |
| Comparison to aviation in terms of emissions | Equal |
| Sulphur dioxide emissions | 15 of the world's largest container ships produce as much as all 760 million cars in the world |
| Sulphur oxide emissions | One large container ship emits the same amount as 50 million diesel-burning cars |
| Sulphur content in bunker fuel | 3% |
| Sulphur content in ultra-low sulphur diesel | Lower than 3% |
| CO2 emissions | One container ship emits as much as 50 million cars |
| Methanol-powered ships | Maersk is planning to launch its first methanol-powered ship in 2023 |
| LNG-powered ships | CMA CGM |
| Biomass gasification | Breaks down biomass into hydrogen and carbon components |
| NOx emissions | Present in ammonia, the next-gen fuel |
| Fuel consumption | 66 gallons per minute |
| Oil price | Affects the significance of fuel-saving measures |
| Fuel-saving measures | Slow steaming, waste heat recovery |
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What You'll Learn
Container ships burn 66 gallons of fuel per minute
The amount of fuel burned by container ships is a significant contributor to their environmental impact. The fuel consumption of a containership depends on its size and cruising speed, with larger ships burning more fuel, especially at higher speeds. For example, a containership of around 8,000 TEU (twenty-foot equivalent units) would consume about 225 tons of bunker fuel per day at 24 knots. At 21 knots, this consumption drops to about 150 tons per day, a 33% decline.
Shipping lines often opt for slower speeds to reduce fuel consumption, but this requires a trade-off with longer shipping times and more ships on a route to maintain schedules. This practice, known as slow steaming, emerged during the 2008-2009 financial crisis and has become the new normal, with over 50% of global container shipping capacity operating under these conditions as of 2011.
The type of fuel used also plays a role in the environmental impact of container ships. The world's 90,000 cargo ships often use low-grade bunker fuel, which contains up to 2,000 times more sulfur than the diesel fuel used in automobiles. This contributes to the emission of sulfur oxides (SOx), with one large ship generating approximately 5,200 tons of sulfur oxide pollution annually.
While container ships burning 66 gallons of fuel per minute is a concern, the issue of ship pollution is multifaceted. While some sources claim that a single large container ship can emit pollutants equivalent to 50 million cars in a year, this may be an exaggeration. Dr. James Corbett, a professor of marine policy, compared the sulfur dioxide produced by a large container ship burning bunker fuel with that of a car burning clean fuel and concluded that 15 of the world's largest ships produced as much sulfur pollution as all 760 million cars. However, this experiment has been criticized for its narrow focus on sulfur pollution and not considering other factors like carbon dioxide.
Overall, while container ships burning 66 gallons of fuel per minute is a concern, the issue of ship pollution is multifaceted and requires a comprehensive approach to address fuel consumption, fuel type, and other emissions beyond just sulfur oxides.
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Shipping contributes to 60,000 premature deaths per year
Shipping emissions are a significant contributor to global air pollution, causing approximately 60,000 premature deaths annually, according to a 2007 study by James Corbett of the University of Delaware and his colleagues. This figure may even be conservative, as epidemiological equations were used to estimate the total number of deaths attributable to shipping emissions. The study found that organic carbon particles and sulphites, emitted primarily from the combustion of shipping fuel, were responsible for about 40,000 deaths per year, or over 60% of shipping emissions-related deaths.
The impact of shipping pollution is not evenly distributed globally. China, home to seven of the ten busiest ports, accounts for more than one-third of premature deaths, with approximately 20,000 deaths attributed to shipping emissions. Other countries significantly impacted include Japan, India, the United Kingdom, and Indonesia, which each reported over a thousand premature deaths linked to shipping pollution.
The United States has a lower impact, with about 1,200 premature deaths per year, due in part to the fuel-switching requirements of the North American Emission Control Area (ECA). However, urban areas like Seattle and San Francisco have per-capita premature mortality rates more than double the global average due to their proximity to major ports.
The health risks associated with shipping emissions are caused by tiny airborne particles, measuring less than 10 micrometres in diameter, which are released during the combustion of shipping fuel. These particles, including carbon, sulphur, and nitrogen oxides, are linked to heart and lung failures as they are small enough to enter the lungs, pass through tissues, and enter the bloodstream.
To address the problem of shipping pollution and reduce premature deaths, researchers recommend transitioning to cleaner fuels, such as low-sulphur fuels, methanol, LNG, and ammonia (NH4). While container ships are more fuel-efficient than individual cars when considering the amount of cargo transported, the shipping industry must still take significant steps to reduce emissions and mitigate health risks for vulnerable populations near major shipping lanes and ports.
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Ships produce sulphur oxide gases
The maritime industry consumes mostly low-grade fuel oil, i.e., heavy oil and diesel oil with high sulphur content compared to other transportation media. The smoke emitted by burning marine fuel contains sulphur oxides, which, in the presence of a catalyst like NO2, will form sulphuric acid, a major cause of acid rain. Sulphur oxides also contribute to the formation of secondary inorganic aerosol gases, fine particles that are harmful to humans.
In 2020, the IMO introduced regulations imposing strict limits on the sulphur content of marine fuels, lowering the maximum percentage of sulphur from 3.5% to 0.5% for all ships operating worldwide. This followed a more limited restriction in place between 2010 and 2015 that only applied to ships operating around the coasts of North America and the North Sea. The rapid phase-out of sulphur in marine fuels likely reduced global SO2 emissions from marine fuels by around 8.5MtSO2 per year, to around 2.5 MtSO2 per year, an abrupt decline of about 10% after 2020.
It is worth noting that the sulphur particles contained in ships' exhaust fumes have been counteracting some of the warming effects of greenhouse gases. However, lowering the sulphur content of marine fuel has weakened this masking effect, contributing to warming. Some researchers have proposed that the drop in SO2 due to the IMO's clean air regulations could be behind a recent spike in global sea surface temperature.
While shipping is responsible for a significant amount of sulphur pollution, it is important to consider other pollutants such as carbon dioxide (CO2) and nitrogen oxides (NOx). The comparison of emissions between ships and cars is complex and depends on various factors. For instance, modern cars have a smaller carbon footprint, but many cars on the road are not modern. Additionally, the payload/fuel ratio of cargo liners is much better than that of cruise ships, and they take significant precautions to save fuel by using low-sulphur fuel, which is pricier.
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Ships are switching to liquefied natural gas
There are various opinions on how much container ships pollute. Some sources claim that a single giant container cargo ship produces more pollution per year than all of the gas cars in America. However, this claim has been disputed by others, who argue that it is exaggerated and false. They point out that the comparison only considers sulfur pollution and does not take into account other types of emissions, such as carbon dioxide. Nonetheless, it is clear that shipping contributes significantly to sulfur pollution and overall emissions, with shipping being responsible for 13% of emissions.
With increasing environmental regulations, ship owners are turning to alternative fuels, and liquefied natural gas (LNG) is becoming a popular choice. LNG is a safe and cost-effective fuel that helps to reduce greenhouse gas emissions and other harmful pollutants. LNG produces significantly lower emissions when burned compared to traditional marine fuels, including lower SOx, NOx, and PM emissions. This not only helps shipowners comply with environmental regulations but also reduces compliance risks. LNG is primarily methane (85-95%) but also contains small amounts of ethane, propane, and other hydrocarbons.
Liquefied natural gas is natural gas that has been cooled to a liquid state, typically to between −145 °C and −163 °C, for shipping and storage. This process reduces the volume of natural gas by about 600 times, making it more economical and feasible for long-distance transport when pipelines are not an option. LNG is loaded onto double-hulled ships for safety and insulating purposes and is then transported to regasification terminals, where it is returned to its gaseous state and distributed via pipelines.
LNG offers several advantages over traditional marine fuels. It is a transition fuel that serves as a step towards decarbonizing the maritime industry. While it does release some carbon, it produces lower emissions and is quieter. LNG-powered ships also have fuel efficiency benefits, with modern dual-fuel engines that can operate on both LNG and traditional fuels, providing flexibility and optimizing fuel consumption.
BioLNG, a renewable fuel produced from biogas, can further reduce the carbon footprint of ships using LNG fuel systems. Additionally, LNG infrastructure is improving, with more vessels being equipped to operate on LNG and the development of dual fuel engines that can utilize LNG and conventional liquid marine fuels.
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Ships are responsible for oil spills
While container ships are a source of pollution, the extent of their pollution in comparison to other sources is debated. Some sources claim that 15 of the world's largest container ships produce as much sulfur pollution as all the world's 760 million cars. However, this claim has been contested, with the conclusion deemed to be exaggerated and false. Nevertheless, shipping is responsible for a significant amount of sulfur pollution, and container ships produce a lot of CO2 compared to cars.
Oil spills are a form of pollution that can have disastrous consequences for the environment, economy, and society. They occur when liquid petroleum hydrocarbons are released into the environment, particularly marine ecosystems, due to human activity. Ships, including tankers, offshore platforms, drilling rigs, and wells, are responsible for oil spills, which can result from accidents, equipment failure, human error, or bad luck. The largest tanker spill on record was the Atlantic Empress disaster, which released an estimated 90 million gallons of oil into the Atlantic Ocean after a collision with another ship during a tropical storm. Another notable oil spill occurred in 1989 when the Exxon Valdez oil tanker capsized, impacting the ecosystem in Alaska. In 2010, the Deepwater Horizon explosion in the Gulf of Mexico killed eleven oil rig workers and released millions of gallons of oil, impacting beach tourism and fishing industries. Oil spills can also occur on land, such as the blowout at a well in Uzbekistan in 1992, which spewed oil that caught fire and burned for two months.
The consequences of oil spills can be felt for decades, and cleanup activities can never remove 100% of the spilled oil. Oil penetrates the structure of the plumage of birds and the fur of mammals, reducing their insulating ability and making them more vulnerable to temperature fluctuations. Oil spills also create an immediate risk of negative effects on human health, including respiratory and reproductive problems, liver damage, and immune system damage. Additionally, they can increase fire hazards and lead to the closure of beaches, parks, and fisheries, impacting tourism and marine resource extraction industries. The responsible parties for oil spills may be held accountable for the cleanup and restoration costs, as established by the Oil Pollution Act of 1990.
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Frequently asked questions
Container ships are major polluters and a tough challenge for the global climate. The shipping industry accounts for about 3% of global greenhouse gas emissions, which is comparable to the total emissions from aviation.
In 2009, Dr. James Corbett, a professor of marine policy at the University of Delaware, theorised that 15 of the world's largest container ships produced as much sulfur pollution as all 760 million of the world's cars. This theory has been widely discredited, but it did highlight the significant sulfur pollution caused by shipping.
Aside from gas emissions, container ships are responsible for water pollution, including ballast water and oil spills, as well as the use of biocides in antifouling paints and the dumping of garbage and sewage.
Some companies are switching to cleaner fuels, such as liquefied natural gas, methanol, and biofuels made from plants. These fuels produce less air pollution and carbon dioxide emissions.
Container ships contribute to water pollution through ballast water discharge, oil spills, and the use of biocides and antifouling paints. These pollutants have disastrous effects on ocean ecosystems, killing over a million seabirds and 100,000 sea mammals annually.
