Ships Polluting Our Air: Understanding Their Impact

Ships are responsible for more than 18% of nitrogen oxides pollution, 3% of greenhouse gas emissions, and contribute to air, water, acoustic, and oil pollution. Ports are often located near densely populated urban areas, exposing millions of inhabitants to additional pollution. The main sources of ship pollution are exhaust gases and ballast water discharges, which are produced by diesel engines that burn high-sulfur content fuel oil, also known as bunker oil. This fuel produces sulfur dioxide, nitrogen oxide, and particulate matter, in addition to carbon monoxide, carbon dioxide, and hydrocarbons, which contribute to the formation of aerosols and secondary chemical reactions in the atmosphere. Ports are also significant sources of pollution, with major air pollutants generated by port activities including carbon monoxide, volatile organic compounds, nitrogen oxides, sulfur oxides, and particulate matter.

Ships burn high-sulphur content fuel oil, producing sulphur dioxide

Ships burn high-sulphur content fuel oil, also known as bunker oil, which produces sulphur dioxide, nitrogen oxide, and particulate matter, in addition to carbon monoxide, carbon dioxide, and hydrocarbons. These emissions lead to the formation of aerosols and secondary chemical reactions, including the formation of HCHO and ozone in the atmosphere.

The combustion process in diesel engines contributes to the production of sulphur dioxide. During combustion, as air contains over 70% nitrogen by volume, some of it reacts with oxygen to form nitrous oxide. The amount of nitrous oxide produced is dependent on the combustion temperature, with higher temperatures resulting in increased production. However, it is important to note that other pollutants, such as unburned or partially burned hydrocarbons (hyperfine particulates or soot), are more prevalent at lower combustion temperatures. This presents a trade-off between nitrogen oxide and soot emissions.

Sulphur dioxide emissions from ships have significant environmental and health impacts. Sulphur dioxide, along with nitrogen oxide, undergoes chemical reactions in the air to form fine particles, sulphate, and nitrate aerosols. These secondary particles, in addition to those directly emitted by ships, such as black carbon, increase the health risks associated with shipping pollution. The tiny airborne particles can enter the lungs and pass through tissues into the bloodstream, triggering inflammations that can lead to heart and lung failure.

To address the issue of sulphur dioxide emissions, the International Maritime Organization (IMO) adopted a sulphur standard for shipping fuels in 2008, which was implemented in 2020. This regulation reduced the permitted sulphur exhaust limit for all marine fuel from 3.5% to 0.5% outside Emission Control Areas (ECAs). Additionally, ships can switch to low-sulphur fuel or alternative fuels, such as liquefied natural gas (LNG), to reduce sulphur dioxide emissions and particulate matter.

Shipping emissions are a major contributor to port pollution

Shipping vessels typically use heavy fuel oil, which is much cheaper than petrol used in land transport. However, it has an extremely high sulphur content—2700 times higher than road fuel. As a result, ships emit large quantities of sulphur dioxide (SO2) and nitrogen oxide (NOx), which contribute to air pollution and have detrimental health effects. In 2005, international shipping in European seas was estimated to emit 1.7 million tonnes of SO2 and 2.8 million tonnes of NOx annually.

The combustion process in engines leads to the production of NOx, and higher combustion temperatures result in increased NOx emissions. Other pollutants, like unburnt or partially burnt hydrocarbons (hyperfine particulates or soot), are more prevalent at lower combustion temperatures. Thus, there is a trade-off between NOx and soot emissions.

To address the issue of shipping emissions, various measures have been proposed and implemented. These include alternative energy sources, such as shore power, which can reduce SOx, NOx, and particulate matter emissions by over 88% while in port. Switching to low-sulphur fuel or alternative fuels can help reduce SOx emissions and particulate matter. Additionally, internal engine modifications, such as water injection and exhaust gas recirculation, can prevent NOx production during combustion. While scrubbers can effectively reduce SO2 emissions, open-loop scrubbers have raised environmental concerns due to their wash-water discharges, which increase pH levels in surrounding waters.

While shipping emissions contribute significantly to port pollution, it is important to acknowledge the efforts made to reduce this pollution. Ports are implementing measures to improve air quality, and the European Parliament has voted for a 2% green hydrogen mandate for shipping. However, more stringent regulations and the widespread adoption of technological solutions are necessary to mitigate the detrimental impact of shipping emissions on air quality and human health.

Shipping accounts for 3% of greenhouse gas emissions

Shipping is a major contributor to global carbon dioxide (CO2) emissions, with the industry accounting for about 3% of the world's greenhouse gas emissions. This figure is expected to increase as the sector grows, with shipping currently carrying more than 80% of world trade.

The maritime transportation industry's carbon footprint is significant, with international shipping alone responsible for a large proportion of global CO2 emissions. Shipping vessels typically run on heavy fuel oil, which is much cheaper than petrol but has a far higher polluting impact. The sulphur content of heavy fuel oil, for example, is 2700 times higher than that of road fuel. As a result, ships are a major source of sulphur dioxide (SO2) emissions, which, along with nitrogen dioxide (NOx) emissions, have severe health impacts. These emissions contribute to an estimated 400,000 premature deaths per year worldwide, at an annual cost to society of over €58 billion.

To address this issue, various measures are being implemented to reduce air pollution from marine shipping. These include the use of alternative energy sources, such as liquefied natural gas (LNG), hydrogen, and biofuels, as well as modifications to ship components and operational efficiencies. For example, shore power, where electrical power is provided to ships while docked, can reduce SOx, NOx, and particulate matter emissions by 88% or more while in port. Additionally, slow steaming, which involves reducing the speed of cargo ships, can lower fuel consumption and greenhouse gas emissions.

Regulatory bodies and governments are also taking action to reduce emissions from the shipping industry. For instance, the International Maritime Organization (IMO) has adopted a sulphur standard for shipping fuels, expected to save 26,000 lives per year in the EU from 2020. Furthermore, the IMO's GHG strategy includes initiatives to enhance the sustainability of the industry, such as harnessing renewable energy sources and transitioning to cleaner alternative fuels.

Despite these efforts, the shipping industry still faces challenges in decarbonizing, particularly given the sector's reliance on fossil fuels. However, with the push for a net-zero future, shipping companies are investing in alternative fuels and emission-cutting technologies. Additionally, a global fee on greenhouse gas emissions has been proposed, with a tax on carbon dioxide emissions from ships, to further incentivize the reduction of pollution.

Shipping's impact on air quality increases as the sector grows

Shipping's impact on air quality is an increasingly pressing issue as the sector continues to grow. Shipping is a highly efficient method of transporting cargo, moving over 80% of the world's goods. However, the sheer size of the industry means that it has a significant environmental impact, particularly in terms of air pollution.

The main sources of air pollution from ships are their diesel engines, which burn high-sulphur content fuel oil, also known as bunker oil. This produces sulphur dioxide, nitrogen oxide, carbon monoxide, carbon dioxide, and hydrocarbons, which contribute to the formation of aerosols and secondary chemical reactions in the atmosphere. In addition, ships' engines produce particulate matter, which has been linked to a range of adverse health effects, including respiratory and cardiovascular diseases, and lung cancer.

The impact of shipping on air quality is particularly notable in port cities, where populations are exposed to high levels of pollution from ships and port activities. Ports are hubs of economic activity, but their proximity to urban areas means that millions of people are at risk of increased pollution levels. Ports are major sources of not only ship pollution but also vehicle emissions, dust, and noise.

To address the issue of air pollution from shipping, various measures are being implemented. These include the use of alternative energy sources, such as shore-side electricity, modifications to ship components, and operational efficiencies. For example, shore power can reduce SOx, NOx, and particulate matter emissions by 88% or more while ships are in port. In addition, ships can switch to low-sulphur fuel or alternative fuels, and the installation of scrubbers can cut SO2 emissions by 99%.

While these technological solutions are available, regulators and the industry must work together to implement them effectively. Reducing air pollution from ships is a complex and costly challenge, but it is a top priority for many governments and organisations working to improve air quality and protect public health.

Shipping emissions are linked to respiratory and cardiovascular diseases, lung cancer, and premature death

Shipping emissions are a major contributor to air pollution, and this has a significant impact on human health. Ships burn hydrocarbon fuels, such as heavy fuel oil, which has a high sulphur content. This produces sulphur dioxide, nitrogen oxide, carbon monoxide, carbon dioxide, and hydrocarbons, which contribute to the formation of aerosols and secondary chemical reactions in the atmosphere.

The health effects of exposure to these pollutants are well documented. Shipping emissions are linked to respiratory diseases, cardiovascular diseases, lung cancer, and premature death. The tiny airborne particles produced by ships can enter the lungs and pass through tissues into the bloodstream, triggering inflammations that can lead to heart and lung failure. These particles have also been linked to an increased risk of cancer. The US Environmental Protection Agency (EPA) has classified diesel exhaust as a likely human carcinogen, and over 30 epidemiological studies have found a direct link between diesel exhaust exposure and cancer risk.

The impact of shipping emissions on air quality and human health is a global issue. In 2005, sulphur dioxide (SO2) emissions from international shipping in the seas surrounding Europe were estimated at 1.7 million tonnes per year, with nitrogen dioxide (NOx) emissions at 2.8 million tonnes, and particulate matter (PM 2.5) at 195,000 tonnes. The growth of the shipping industry has led to an annual increase in emissions, overwhelming gains made through efficiency measures such as slow-steaming.

To address the health and environmental impacts of shipping emissions, regulators and the industry have implemented various measures. These include alternative energy sources, such as shore-side electricity, modifications to ship components, and the use of low-sulphur fuels or scrubbers to reduce emissions. Ports are also taking steps to reduce pollution, with some offering discounts to shipowners with vessels that have higher energy efficiency ratings.

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