Boats' Pollution: Understanding Their Environmental Impact

Boats and shipping are a major source of water pollution and air pollution. While individual boats and marinas release only small amounts of pollutants, when multiplied by the thousands of boaters and marinas, they can cause distinct water quality problems in lakes, rivers, and coastal waters. Sewage discharge from boats can cause bacterial and viral contamination of fisheries and shellfish beds, producing risks to public health. Spills and leaks of fuel, oil, and other chemicals used to maintain and repair boats also contribute to water pollution. In addition, ships produce significant air pollution and noise pollution, which can harm marine species and human health.

Sewage and waste

Cruise ships also contribute significantly to sewage pollution. A large cruise ship can generate around 150,000 gallons of sewage and greywater during a week's voyage, according to some sources, while others state that a 3000-passenger cruise ship can produce 210,000 gallons of sewage in the same period. This sewage includes waste from toilets and health facilities on the ship and is rich in bacteria and algae, which can adversely affect marine life and ecosystems. Cruise ships also produce oily bilge water, bio-waste, and other hazardous waste.

In addition to sewage, boats and cruise ships also generate solid and liquid waste, such as food waste, cans, bottles, plastics, and garbage. This waste can be dumped into the ocean or sea, further contributing to marine pollution. Federal law in the United States prohibits the release of waste of any kind into U.S. waters, including trash, garbage, oil, and other liquid pollutants. The improper disposal of toxic substances can result in civil and criminal penalties, including fines and imprisonment.

Air pollution

Marine shipping is the most energy-efficient mode of transport for large cargo volumes, but it still burns hydrocarbon fuels for energy, emitting air pollution that degrades air quality and adversely affects human health.

Commercial ships emit several types of air pollution, including greenhouse gases (GHG), nitrogen oxides (NOx), sulphur oxides (SOx), and particulate matter. GHGs, such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), contribute to climate change and ocean acidification by trapping the sun's heat. In Canada, the climate change caused by GHGs has led to increased average and extreme temperatures, shifting rainfall patterns, permafrost thawing, and more hazardous weather. These extreme weather events, including heat waves, floods, and major storms, negatively impact human health and cause premature deaths worldwide.

Nitrogen oxides (NOx) and sulphur oxides (SOx) emissions from ships also have significant health impacts. In Europe, shipping in the Baltic Sea, North Sea, and English Channel releases over 800,000 tonnes of airborne nitrogen annually, exacerbating the issue of eutrophication. Sulphur in the air creates acid rain, damaging crops and buildings and causing respiratory issues when inhaled. Additionally, through chemical reactions in the air, SOx and NOx can transform into sulphate and nitrate aerosols, respectively, which contribute to the health impacts of shipping pollution. These 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 these issues, several measures have been proposed and implemented. The International Maritime Organization (IMO) adopted stricter standards for sulphur content in marine fuels, which are expected to save 26,000 lives annually in the EU. Ships can also install scrubbers to reduce SO2 emissions, although the wash-water discharges from open-loop scrubbers have raised environmental concerns. Other methods, such as water injection, exhaust gas recirculation, and humid air motors, can help reduce NOx production during combustion, but they may not meet Tier III standards alone.

Additionally, ports are taking initiatives to improve air quality. For example, the Port of Halifax implemented shore power, reducing engine idling and decreasing GHG and air pollutant emissions. The European Parliament has also voted for a 2% green hydrogen mandate for shipping, although some argue that more ambitious actions are needed.

Water pollution

Boats and boating activities can cause water pollution in several ways. Firstly, they can contribute to oil and gas pollution in water bodies. This can occur through engine leaks, improper engine maintenance, or the discharge of uncombusted fuel from engines. Old two-stroke engines are particularly problematic, emitting up to 30% of their gas or oil mixture into the water. Upgrading to four-stroke engines can significantly reduce this issue, as they emit up to 97% less water and air pollution.

Additionally, boats can release chemicals and solvents used for maintenance and repair, such as paints, oils, and cleansers, which are harmful to aquatic life. For example, chlorine, ammonia, and phosphates found in many boat cleaners can damage plankton and fish populations. Poorly maintained sanitary waste systems on boats and at marinas can also increase bacteria and nutrient levels in the water, further contributing to water pollution.

The design and location of marinas play a significant role in water quality. Poorly planned marinas can disrupt natural water circulation, cause shoreline soil erosion, and lead to habitat destruction. Marinas should be strategically located and designed to facilitate natural flushing and renew the water regularly.

Another often-overlooked form of pollution caused by boats is noise pollution. It can disrupt communication between marine animals, impacting their ability to find food, avoid predators, and mate. Noise pollution can also drive animals to relocate to less suitable habitats or shallow waters, endangering their health. Reducing speed and maintaining engines properly can help mitigate this issue.

Plastic pollution

The primary sources of plastic pollution in the marine environment are land runoff, paint shed from shipping, discarded fishing gear, and littering. Coastal cities in middle-income countries are the world's plastic emissions hotspots, as they are often located near rivers that carry plastic from land to sea. Rivers are the primary transporters of plastic from land to sea, and coastal cities with ineffective waste management systems are particularly vulnerable to plastic emissions.

Once in the ocean, plastic can persist for long periods, as it does not easily decompose. Over time, plastic breaks down into smaller pieces called microplastics, which can be ingested by marine animals and enter the food chain. Microplastics have been found in drinking water, salt, beer, and even in the soil where we grow our vegetables. They have also been found in the bodies of marine animals, including fish, seabirds, and apex predators such as great white sharks and orcas. The ingestion of plastic can lead to starvation, suffocation, and internal injuries, and can also release toxic chemicals into the bodies of marine animals, with disastrous consequences for their health.

To address the issue of plastic pollution, it is essential to reduce the production of plastic, improve waste management systems, and promote the reuse, recycling, and repurposing of plastic materials. Public and private investment is needed to develop infrastructure that supports the circular economy and reduces the environmental impact of plastic. A global plastics treaty is also necessary to reduce plastic production, phase out harmful subsidies, and eliminate products and chemicals that contribute to plastic pollution.

Noise pollution

Most of the underwater noise emitted by ships comes from propeller cavitation, which is a complex phenomenon that can be addressed through design changes to the propeller and the hull of the ship. The engine also contributes noise, which can be mitigated by placing the engine on mounts so it does not touch the hull. In 2017, the shipping company Maersk modified several of its ships by installing efficient propellers and reconfiguring hulls, resulting in a 75% reduction in noise energy emitted.

Cargo ships can emit as much as 190 decibels of noise, which is much louder than a plane taking off and about the same noise level as a rock concert. This noise can interfere with marine mammals' ability to hear natural sounds in the ocean, disrupting their natural behaviours and communication. Marine mammals such as dolphins and toothed whales rely on echolocation, and excessive noise can disrupt these signals, causing the animal to become disoriented and unable to hunt successfully.

Small recreational boats are also a dominant source of underwater noise in coastal areas, particularly in shallow waters. Acoustic monitoring has shown that small vessels can lead to significant and potentially harmful increases in noise levels.

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