What are the key emissions from ships—and how is the maritime industry working to reduce them?
The air around ports can be as polluted as a major highway. Ships idling at berth, burning low quality fuel oil, quietly emit tons of harmful pollutants—many invisible, but all impactful.
From carbon dioxide and sulfur oxides to particulate matter and black carbon, maritime emissions are an often overlooked contributor to climate change and public health risks.
But thanks to growing awareness and mounting pressure, the maritime industry is working toward a cleaner future. Alternative fuels, new regulations, and emission-reduction technologies are promising steps forward—but will require quick action, as emissions related to shipping are projected to grow to 10% of all global greenhouse gas (GHG) emissions by 2050.
To understand the solutions that can help the industry reach zero emissions, we first need to understand the problem: what maritime emissions are, where they come from, and why they matter.
What are maritime emissions?
Maritime emissions refer to the pollutants released into the atmosphere and marine environment by vessels operating in oceans, ports, and various waterways.
Carbon dioxide (CO₂): The leading GHG emitted by ships and the largest contributor to climate change, CO₂ traps heat as it accumulates in the atmosphere. Currently, the shipping industry accounts for nearly 3% of global CO₂ emissions.
Sulfur oxides (SOₓ): NOₓ and hydrocarbons react with sunlight to produce ozone—a major component of smog—and contribute to respiratory diseases like asthma and COPD. NOₓ also forms particulate matter which adds to the PM problem (see PM below).
Particulate matter (PM): Tiny particles released from ship exhaust can penetrate the lungs, causing chronic respiratory diseases and heart conditions.
Black carbon: Produced by the incomplete combustion of fuels, black carbon is a soot-like substance that absorbs sunlight, darkens snow and ice surfaces, and accelerates Arctic ice melt.
Methane (CH₄): Methane slip occurs when unburned methane escapes from LNG-powered vessels. Methane is 84 times more potent than CO₂ over a 20-year timescale, making it a significant climate concern.
Hydrocarbons (HC): Hydrocarbons emitted in the exhaust are products of incomplete combustion (essentially unburned fuel) and react with NOₓ and sunlight to produce ozone, a major component of smog. Many HC are often toxic air pollutants that are known to cause cancer and other health related issues.
The impact of maritime emissions
Maritime emissions trigger a cascade of environmental and public health challenges. From rising global temperatures to localized health risks in port communities, their effects are wide- ranging and increasingly urgent.
Climate change
Greenhouse gases like carbon dioxide (CO₂) and methane (CH₄) trap heat in the atmosphere for centuries, driving long-term global warming. Meanwhile, short-lived pollutants like black carbon have outsized regional impacts—particularly in polar regions where they accelerate Arctic ice melt and sea level rise. These disruptions ripple through marine ecosystems and contribute to more frequent and severe weather events.
Ocean acidification, driven by CO₂ absorption, also threatens coral reefs and endangers marine biodiversity. Without aggressive emissions reduction, maritime pollution will continue to compound these climate risks.
Air quality and public health
Airborne pollutants from ships—primarily SOₓ, NOₓ, HC, and PM—directly degrade air quality and threaten human health.
Port communities bear the brunt of these health consequences. According to the International Council on Clean Transportation, emissions from ships contribute to an estimated 60,000 premature deaths annually worldwide, with high concentrations of pollutants around coastal cities like San Francisco, Singapore, and Hong Kong. These pollutants are associated with higher rates of asthma, heart disease, and lung cancer.
Ecosystem impacts
Maritime emissions disrupt marine and coastal ecosystems. Sulfur compounds, particularly sulfur dioxide (SO₂), contribute to acid rain, endangering fish and other aquatic species. Both SO₂ and CO₂. contribute to ocean acidification. Increased nitrogen levels can also trigger harmful algal blooms, depleting oxygen in the water and leading to dead zones where marine life cannot survive.
How the maritime industry is reducing emissions
These industry measures aim to minimize the footprint of maritime emissions while ensuring compliance with evolving regulations:
Shore power (cold ironing)
When ships dock at port, they often rely on onboard engines to generate power—releasing CO₂, PM, and other pollutants into the surrounding air. Shore power allows ships to plug into the local electrical grid, cutting emissions from those auxiliary engines while at berth. However, shore power does not reduce emissions from other onboard systems like boilers that may still run while docked. The grid also produces CO₂ emissions, so it is simply transferring the problem.
Exhaust treatment technologies
Many vessels are equipped with scrubbers, which remove SOₓ from exhaust gases before they are released into the air. While effective at reducing SOₓ pollution, scrubbers do not eliminate CO₂ NOₓ, or black carbon, leaving major greenhouse gas emissions unaddressed.
Operational efficiencies
Slow steaming—reducing a ship’s speed—lowers fuel consumption and emissions, while AI- driven route optimization minimizes unnecessary fuel use by identifying the most efficient paths. Though helping to mitigate certain pollutants, none provide a comprehensive approach to capturing and controlling all harmful emissions.
Alternative fuels
Ammonia and hydrogen can be produced from renewable sources, offering the promise of near- zero emissions. Methanol, produced from biomass or captured carbon, also provides a cleaner option. However, widespread adoption is challenged by high production costs and significant infrastructure investments.
Emissions capture and control
Advanced emissions capture and control solutions, such as those developed by STAX, help vessels comply with regulations while significantly reducing their environmental footprint.
Unlike scrubbers and shore power, which require specialized port infrastructure or modifications to individual vessels, STAX’s technology attaches to any vessel’s exhaust system to remove pollutants at the source.
Now, with the integration of carbon capture technology, STAX is taking emissions control even further by trapping CO₂ before it escapes into the atmosphere to provide the most comprehensive emissions reduction solution available today.
STAX for maritime emissions reduction
Driven by climate goals and growing public demand for cleaner air and water, the shipping industry is accelerating its shift to more sustainable operations.
Emissions capture and control technologies provide an immediate solution for mitigating pollution, allowing maritime companies to meet environmental targets without waiting for long-term fuel transitions.
STAX is at the forefront of this shift, providing flexible, mobile technology that doesn’t require costly infrastructure or vessel modifications. Vessel and terminal operators can book STAX by the hour while their ship is at berth, making it a cost-effective solution for emission reductions, regardless of port capabilities.
Help your fleet achieve sustainability goals and meet compliance requirements. Read more about STAX’s technology.
