How Boats Pollute The Air And What We Can Do

Boats and ships are a major source of air pollution, contributing to the degradation of air quality, adverse health effects, and climate change. The burning of high-sulfur content fuel oil, diesel engines, and hydrocarbon fuels leads to the emission of sulfur dioxide, nitrogen oxide, carbon monoxide, and particulate matter. These emissions have severe health impacts, causing approximately 400,000 premature deaths annually worldwide and costing society over €58 billion. Shipping's impact on air quality is expected to increase with the sector's growth, and while technological solutions exist, their implementation is crucial to mitigating the environmental and health consequences. Marinas and recreational boating activities also contribute to non-point source pollution through chemical spills and unmaintained sanitary systems.

Shipping's impact on air quality

Shipping has a detrimental impact on air quality, which is only increasing as the sector grows. Ships are responsible for more than 18% of nitrogen oxides pollution and 3% of greenhouse gas emissions. The large diesel engines on ships burn high-sulfur content fuel oil, also known as bunker oil, which produces sulfur dioxide, nitrogen oxide, and particulate matter, as well as carbon monoxide, carbon dioxide, and hydrocarbons. These emissions contribute to ozone and carbon monoxide in the air, which has a range of adverse health effects.

Ships create air pollution that degrades air quality, adversely affects human health, and contributes to the wide-reaching effects of climate change. The tiny airborne particles emitted by ships are linked to premature deaths, with around 400,000 premature deaths per year worldwide attributed to poor air quality caused by international shipping, at an annual cost to society of over €58 billion. These particles enter the lungs and are small enough to pass through tissues and enter the blood, triggering inflammations that can eventually cause heart and lung failure. Ship emissions may also contain carcinogenic particles, with diesel exhaust classified as a likely human carcinogen by the U.S. Environmental Protection Agency (EPA).

Technological solutions to reduce emissions are available, such as shore-side electricity, alternative fuels like liquefied natural gas (LNG), and the installation of scrubbers to cut sulfur dioxide emissions. However, the implementation of these solutions has been slow, and the growth in emissions continues to overwhelm gains in efficiency. The substantial tax privileges enjoyed by the shipping industry have contributed to the growing emissions problem.

Some ports and governments are taking steps to improve air quality. For example, the Port of Montreal has reduced its GHG emissions by 33% since 2007, and the Port of Halifax has implemented shore power, reducing engine idling and associated emissions. The European Parliament has also voted for a 2% green hydrogen mandate for shipping, but more action is needed to address the impact of shipping on air quality.

Scrubbers and other technological solutions

Marine transport is a highly energy-efficient way of moving cargo. However, like all forms of transport that burn hydrocarbon fuels, ships create air pollution that degrades air quality, adversely affects human health, and contributes to the wide-reaching effects of climate change.

To address this issue, the International Maritime Organization (IMO) has set limits on sulphur content in fuels for marine transport. Ships can comply with these new standards by burning low-sulphur fuels or by installing scrubbers, also known as exhaust gas cleaning systems (EGCS). The number of ships with scrubbers has grown from just three in 2008 to over 4,300 in 2020.

Scrubbers are effective at reducing sulphur dioxide (SO2) emissions by 99%. They work by spraying exhaust gases with water to remove SOx, creating acidic washwater that is then discharged into the aquatic ecosystem. However, scrubbers do not address the issue of NOx production during the combustion process. To prevent this, other techniques such as water injection and exhaust gas recirculation (EGR) for 4-stroke engines can be used. Another method is to add water vapour to the combustion air to reduce NOx emissions.

While scrubbers can help reduce air pollution, they have been criticised for simply turning an air pollution problem into an ocean pollution problem. The washwater from scrubbers contains not only sulphur but also a range of other toxic polluting substances, including carcinogens such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals. These substances are highly toxic to marine life, including zooplanktonic organisms, which are central components of marine food chains. As a result, some have called for unilateral action to restrict or prohibit scrubber discharges, and for the IMO to consider prohibiting the use of scrubbers on new ships and phasing them out on existing ships.

Other technological solutions to reduce air pollution from marine transport include shore-side electricity, which can reduce engine idling and decrease GHG emissions. The Port of Halifax, for example, implemented shore power in 2013, resulting in a 7% reduction in engine idling and a decrease of 370,000 kg of GHG and air pollutant emissions. The Port of Montreal has also made efforts to reduce emissions, providing liquefied natural gas (LNG) refuelling for commercial vessels and reducing GHG emissions from port operations by 33% since 2007.

The environmental impact of boating activities

To address air pollution from boating activities, several measures have been proposed and implemented. These include the adoption of alternative fuels, such as liquefied natural gas (LNG), and the installation of scrubbers to reduce emissions of sulfur dioxide and other pollutants. While scrubbers offer a potential solution, there are concerns about the environmental impact of wash-water discharges from open-loop scrubbers, which can increase pH levels in surrounding waters. As a result, open-loop scrubbers are not considered a sustainable option for marine sulphur standards. Other techniques, such as water injection, exhaust gas recirculation, and the use of humid air motors, can help reduce nitrogen oxide emissions during the combustion process.

In addition to air pollution, boating activities also contribute to water pollution. Marinas and recreational boating activities can lead to nonpoint source pollution through the spillage or discharge of chemicals, oils, paints, cleansers, and uncombusted fuels into the water. Poorly maintained sanitary waste systems aboard boats and inadequate pump-out stations at marinas can further elevate bacteria and nutrient levels in the water, degrading water quality and posing risks to aquatic ecosystems.

Furthermore, the boating industry's contribution to greenhouse gas emissions and climate change cannot be overlooked. Ships are responsible for approximately 3% of global greenhouse gas emissions, and the sector's growth overwhelms gains made through efficiency improvements. The high tax privileges enjoyed by the shipping industry have also contributed to increasing emissions. To mitigate this impact, regulators are encouraged to mandate the adoption of technological solutions, such as shore-side electricity, to reduce the carbon footprint of boating activities.

The health impact of air pollution from boats

Air pollution from boats and ships is a leading threat to human health worldwide. Shipping vessels with engines run on heavy fuel oil, which is cheaper than petrol but has a high polluting impact. The sulphur content of heavy fuel oil is 2700 times higher than that of road fuel. Marine shipping is the most energy-efficient way to move large volumes of cargo, but like all other forms of transportation that burn hydrocarbon fuels for energy, ships create air pollution that degrades air quality and adversely affects human health.

The health effects of prolonged exposure to ship emissions include respiratory diseases, cardiovascular disease, lung cancer, and premature death. A recent study found that emissions from diesel engines, commonly used in the freight industry, are significantly more harmful to humans than those from petrol vehicles. More than 30 human epidemiological studies have found that diesel exhaust exposure directly increases cancer risk. In addition to diesel exhaust, the negative health effects of exposure to inhalable particulate matter are also well documented.

In 2019, ambient air pollution, particularly particulate matter (PM) and ozone (O3), was responsible for approximately 4.5 million premature deaths worldwide. Ship traffic is globally increasing and is becoming an important source of air pollution, especially in coastal areas. Sea transport accounts for 80% of goods transported worldwide, and the demand for sea trade is expected to grow by almost 40% by 2050.

In 2005, in the seas surrounding Europe, sulphur dioxide (SO2) emissions from international shipping were estimated at 1.7 million tonnes a year, nitrogen dioxide (NOx) emissions at 2.8 million tonnes, and particulate matter (PM 2.5) at 195,000 tonnes. Due to the application of the 0.1% MARPOL limit in Sulphur Emissions Control Areas (SECAs) in the North and Baltic Sea and English Channel since 2015, ship-sourced sulphur emissions have reduced considerably in these areas.

Technological solutions like shore-side electricity are available, but regulators should require the industry to implement them. Ports are critical to economies worldwide and are hubs of economic activity, but they are also major sources of ship pollution, vehicle emissions, dust, and noise. Ports are often close to heavily populated urban areas, exposing millions of inhabitants to additional pollution.

The cost of shipping air pollution

One of the main contributors to shipping air pollution is the burning of high-sulfur content fuel oil, also known as bunker oil, in diesel engines. This process produces sulfur dioxide, nitrogen oxide, and particulate matter, as well as carbon monoxide, carbon dioxide, and hydrocarbons. These emissions lead to the formation of aerosols and secondary chemical reactions, resulting in ozone, HCHO, and other harmful substances. The US Environmental Protection Agency (EPA) has classified diesel exhaust as a likely human carcinogen, highlighting the serious health risks associated with shipping air pollution.

The impact of shipping air pollution is not limited to the atmosphere but also extends to the oceans. Nitrogen oxide emissions from ships, for example, contribute to the increasing acidification of the oceans, which can have far-reaching consequences for marine ecosystems and the organisms that depend on them. Furthermore, the application of the MARPOL limit on sulfur emissions in the North and Baltic Seas and the English Channel has resulted in a significant reduction in ship-sourced sulfur emissions in these regions. This success story demonstrates that regulatory measures can effectively mitigate shipping air pollution.

To address the issue of shipping air pollution, various solutions have been proposed and implemented. One approach is to install scrubbers on ships, which can reduce sulfur dioxide emissions by 99% and decrease other polluting particles. However, open-loop scrubbers have faced criticism due to their wash-water discharges, which contribute to higher pH levels in surrounding waters. Other methods, such as internal engine modifications like water injection and exhaust gas recirculation, aim to prevent NOx production during the combustion process. While these techniques are beneficial, they may not be sufficient to meet the Tier III standard for emissions reduction.

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