Ships Vs Land Transport: Who's The Bigger Polluter?

Shipping is a vital part of the global economy, with seagoing vessels carrying over 12 billion tons of cargo in 2023. However, the industry also contributes significantly to climate pollution, particularly through the emission of sulphur oxides, nitrogen oxides, and carbon dioxide. While it is challenging to make a direct comparison between the polluting effects of ships and land transport, some estimates indicate that the international shipping industry produces as much carbon dioxide as a large country like Germany. Additionally, a 2009 study by Dr. James Corbett suggested that 15 of the world's largest container ships could produce as much sulfur pollution as all 760 million cars globally. However, this conclusion has been disputed, and the shipping industry is taking steps to reduce its environmental impact, such as transitioning to cleaner fuels and improving fuel efficiency.

Sulfur emissions from ships

In 2020, the United Nations' International Maritime Organization (IMO) imposed a sulfur cap, limiting the sulfur content in ship fuel to 0.5%, down from 3.5%. This regulation aimed to reduce atmospheric sulfur oxide emissions, which pose a threat to public health and the environment. The cap has been successful, with a 70% drop in sulfur oxide emissions from shipping observed in the following year.

To comply with the new regulations, most ships switched to cleaner, less polluting fuels. However, the IMO also allows countries to certify "alternative mechanisms," such as exhaust gas cleaning systems or "scrubbers." These scrubbers treat the sulfur emissions before they are released into the sea, rather than requiring a switch to cleaner fuels. While scrubbers can reduce air pollution, they have been criticized for diverting sulfur emissions from the air to the ocean, often without adequate treatment of the contaminated water. The guidelines for assessing the environmental risk of scrubber discharge have been criticized as inadequate, and there are concerns about the potential impact on marine life.

The reduction in sulfur emissions from ships has had a visible impact on the environment. Ship tracks, the polluted marine clouds that trail ocean-crossing vessels, have decreased significantly due to the lower sulfur content in ship fuel. These clouds, visible from space, are like "ghostly fingerprints" tracing shipping lanes globally. The decrease in ship track formation indicates that the IMO's sulfur cap has successfully reduced air pollution from shipping.

While the IMO's sulfur cap has positively impacted air quality, it is important to consider other aspects of shipping's environmental impact. According to the International Council on Clean Transportation (ICCT), international shipping contributes significantly to carbon dioxide (CO2) emissions. In 2015, shipping produced 812 million tonnes of CO2, equivalent to the emissions of the sixth-largest emitter country. Container ships are the largest producers of CO2, followed by bulk carriers and oil tankers. Modern ships are designed to be more fuel-efficient, and alternative power sources, such as battery power and sails, are being explored to further reduce emissions.

In conclusion, the IMO's sulfur cap has successfully reduced sulfur emissions from ships, improving air quality and reducing the environmental impact of shipping. However, the diversion of emissions from air to ocean due to scrubber use highlights the need for comprehensive regulations that consider the overall ecological impact of the shipping industry.

CO2 emissions from land transport

The transport sector is a significant contributor to global CO2 emissions, accounting for around one-fifth of total emissions. Within the transport sector, road transport is the largest contributor, responsible for three-quarters of transport emissions. Passenger vehicles, including cars and buses, are the dominant source, making up 45.1% of road transport emissions. Trucks carrying freight contribute an additional 29.4%.

Efforts have been made to reduce emissions from road transport, such as the increasing deployment of electric vehicles. However, the impact of these efforts has been limited, and emissions from the transport sector have remained relatively stable in recent years. According to projections, road transport emissions are expected to decrease in the coming years, but this decrease will be offset by increases in aviation and maritime emissions.

The International Energy Agency (IEA) predicts that global transport will increase in the coming decades due to population growth, rising incomes, and increased access to cars, trains, and flights. This will result in a significant rise in transport emissions, highlighting the urgent need for more effective emission reduction strategies.

To achieve net-zero CO2 emissions from global energy by 2070, the IEA's Sustainable Development Scenario outlines pathways for different transport sub-sectors to decarbonize. For example, emissions from motorcycles are expected to be phased out by 2040, rail by 2050, and small trucks by 2060. However, emissions from cars and buses are not projected to be completely eliminated until 2070, and other transport sectors, such as aviation and maritime, will pose significant challenges in the path towards decarbonization.

Health risks of shipping pollution

Shipping pollution has been linked to a range of health risks, including respiratory issues, lung cancer, heart disease, and stroke. According to a study by the World Health Organization, air pollution kills as many people as tobacco, making it a significant health concern.

The health risks associated with shipping pollution are primarily due to the emission of harmful pollutants such as carbon dioxide, sulfur dioxide, nitrogen oxide, and particulate matter. These pollutants can have both direct and indirect impacts on human health. For example, sulfurous particles from ship fuel can infiltrate human lungs, pass into the bloodstream, and thicken blood vessels, increasing the risk of cardiovascular and respiratory problems.

One of the most significant health risks of shipping pollution is the emission of sulfur dioxide, which has been linked to asthma and cancer. It has been estimated that a single giant container ship can emit as much cancer and asthma-causing chemicals as 50 million cars. The low-grade bunker fuel or fuel oil used by ships can contain up to 2,000 times more sulfur than the diesel fuel used in automobiles, contributing to the high levels of sulfur dioxide emissions.

In addition to air pollution, shipping activities also contribute to water pollution, which poses risks to public health. Blackwater and greywater discharges from ships can contain harmful bacteria, viruses, intestinal parasites, and nutrients that can contaminate fisheries and shellfish beds. Oil spills, both accidental and intentional, are another significant source of water pollution, posing risks to marine ecosystems and potentially impacting human health through the consumption of contaminated seafood.

The impact of shipping pollution on human health is particularly pronounced in coastal regions and port cities, where emissions from ships can mix with the atmosphere and affect the air quality. A study focusing on East Asian shipping vessels found that shipping emissions accounted for 16% of global shipping carbon dioxide emissions, with 60% of their pollution occurring within 20 nautical miles of the shore. This proximity to populated coastal areas increases the health risks for those living nearby.

Regulations on shipping emissions

The International Maritime Organization (IMO) has been working on reducing greenhouse gas emissions from ships since 1997, when it revised the International Convention for the Prevention of Pollution from Ships, or MARPOL. In 2003, the IMO adopted a resolution urging the development of mechanisms to reduce greenhouse gas emissions from ships.

In 2011, the IMO included marine GHG emission reduction in its regulatory framework, and GHG emissions from international shipping began to be regulated by revising Annex VI of MARPOL. The regulatory phases of MARPOL 73/78 include applying new building regulations on NOx to ships equipped with 130 kW or above diesel engines. The IMO has also mandated that the upper limit on the sulfur content of ships' fuel oil be reduced to 0.50% from 3.50%, except in designated Emission Control Areas, where the limit is already 0.10%.

In 2023, the IMO approved net-zero regulations for global shipping, aiming for net-zero emissions by or close to 2050. These regulations will set mandatory marine fuel standards and GHG emissions pricing for shipping to address climate change. The IMO Net-Zero Framework will be included in a new chapter of Annex VI of MARPOL and will be formally adopted in October 2025 before entering into force in 2027. The regulations will require ships to comply with a global fuel standard and a global economic measure.

In addition to the IMO, other organizations such as the European Commission and individual countries have also implemented regulations to reduce emissions from the shipping sector. For example, since January 2018, large ships over 5,000 gross tonnage loading or unloading cargo or passengers at ports in the European Economic Area (EEA) must monitor and report related GHG emissions. The European Commission has also adopted implementing acts, such as the Commission Implementing Regulation (EU) 2023/2599, which lays down rules for the administration of shipping companies by administering authorities.

While these regulations are a step in the right direction, it is important to note that the progress of shipping carbon emissions is affected by unknown "innovative measures, fuels, and technologies." Appropriate laws and policies are needed to regulate the shipping industry and achieve decarbonization targets.

Alternative fuels for ships

The shipping industry is exploring alternative fuels to reduce its environmental footprint and comply with international regulations aimed at decreasing greenhouse gas emissions. Here are some of the alternative fuels being considered and implemented:

Liquefied Natural Gas (LNG)

LNG is increasingly being adopted as a fuel for shipping due to its potential to significantly reduce emissions. LNG has already overcome the hurdles of international legislation, and its use is expected to reduce greenhouse gas emissions and make maritime operations more sustainable. LNG accounts for about 24% of the energy consumed by ships, which is roughly equivalent to the amount of heavy fuel oil (HFO) and marine gas oil (MGO) consumed by ships combined.

Liquefied Petroleum Gas (LPG)

Liquefied Petroleum Gas (LPG) is another promising alternative fuel for the maritime industry. LPG offers a cleaner and more sustainable option for powering ships, with lower greenhouse gas emissions and a near elimination of sulphur emissions compared to conventional maritime fuels.

Hydrogen

Hydrogen is a promising candidate for zero-emission operation. Green hydrogen, produced through electrolysis powered by renewable energy, is key to sustainability. When used in fuel cells, it generates electricity with only water vapour as a byproduct, eliminating harmful pollutants. However, hydrogen's low energy density compared to conventional fuels requires larger storage tanks, impacting ship design and cargo capacity.

Ammonia

Ammonia is also being explored as a potential green fuel for propelling ships. Its high energy density and low viscosity make it suitable for long-range shipping operations. However, the widespread adoption of ammonia faces challenges related to storage and bunkering infrastructure, requiring specialised equipment and facilities that are currently limited in the shipping industry.

Biofuels

Biofuels are emerging as promising alternatives to traditional fossil fuels in the shipping industry. They offer a potential pathway to reduce greenhouse gas emissions and advance towards a more sustainable future. The maritime sector is exploring a wide variety of biofuels, including Fatty Acid Methyl Esters (FAME), hydrotreated vegetable oils (HVO), biomass-to-liquid (BTL) products, glycerol, and straight vegetable oil (SVO) products.

Methanol

Methanol is another alternative fuel that is being considered for maritime applications. It is expected to overcome legislative hurdles soon and contribute to the industry's transition to cleaner and more sustainable operations.

The exploration and adoption of these alternative fuels demonstrate the shipping industry's efforts to reduce its environmental impact and contribute to a more sustainable future.

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