Last updated on March 10, 2026
Understanding the role of emission capture and control technology in reducing maritime pollution and achieving at-berth compliance.
Ocean-going vessels transport 80% of global goods—more than 10 billion tons annually. While essential to international trade, ships emit significant air pollutants both at sea and while docked at ports that are harmful to the environment and public health.
Regulators worldwide are tightening emissions standards. At berth, California has enacted the most stringent port air-quality regulations in the world. Under the California Air Resources Board (CARB), vessels must use either shore power or a CARB-approved Capture and Control Emissions Control Strategy (CAECS).
As the maritime industry moves toward the International Maritime Organization’s (IMO) goal of achieving net-zero shipping emissions “by or around” 2050, emissions capture and control service providers like STAX—which offer shippers and companies a flexible and cost-effective solution—have emerged as a flexible compliance tool.
This article will answer commonly asked questions about emissions capture and control systems, including how they work, whether they’re effective, and where ships can access them today.
What technologies reduce maritime at-berth emissions?
Air pollution that comes from docked vessels can be reduced through a handful of technologies:
- Shore power, which allows ships to turn off their engines and plug into the electrical grid
- Cleaner fuels, such as liquefied natural gas (LNG), methanol, or ammonia
- Exhaust gas cleaning systems, often called scrubbers
- Emissions capture and control systems, like STAX
For at-berth compliance under CARB regulations, only two solutions qualify:
- Shore power systems
- CARB-verified Capture and Control Emissions Control System (CAECS)
What is emissions capture and control technology?
Emissions capture and control technology, like STAX’s, is a system that attaches directly to a ship’s exhaust ducts, while the vessel is at berth, and filters harmful pollutants before they enter the atmosphere. These systems are particularly useful for:
- Vessels not equipped for shore power
- Ports without full electrification infrastructure
- Operators seeking flexible, short-term compliance solutions
How does emissions capture and control work?
Capture and control systems connect to a vessel’s exhaust stacks using flexible ducting. Polluted exhaust gases are pulled into a filtration unit, where emissions like nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter (PM) are then removed before a purified gas is released.
- STAX’s XCAP system has the longest placement arm in the industry, spanning over 250 feet, which allows it to reach nearly any vessel configuration, even in the most congested ports.
- Equipped with two ducts that attach to a ship’s exhaust pipes, emissions are pulled into the STAXbox purification system. Harmful air pollutants are then purified into a pollution-stripped gas.
What are the benefits of emissions capture and control vs shore power?
When comparing emissions capture and control systems like STAX to shore power, several key benefits are clear:
Infrastructure flexibility and vessel compatibility
Shore power requires dedicated portside infrastructure and oftentimes, vessel retrofits. Emissions capture systems can be deployed to container ships, roll-on/roll-off (ro-ro) vessels, and tankers without permanent modifications.
Additionally, shore power depends on grid capacity and landside electrical upgrades. Emissions capture systems operate independently of the grid.
Lower costs
Shore power involves high upfront costs that may require years to integrate into a budget. It also comes with associated electrical utility fees. Emissions capture technology reduces emissions without substantial investment or extra utility costs.
Emissions coverage
Shore power eliminates auxiliary engine emissions but does not address boiler emissions. Emissions capture systems treat both.
Are there alternatives to electrifying ports?
Yes. While electrification is a long-term decarbonization strategy, mobile emissions capture systems offer an alternative pathway, particularly for:
- Developing ports
- Congested terminals
- Older vessels that cannot easily be retrofitted
- Ports facing grid limitations
This makes capture and control a complementary strategy to electrification, rather than a competing one.
How can developing ports reduce emissions?
Developing ports often face financial and infrastructure constraints that make rapid electrification difficult. Mobile capture systems allow ports to:
- Reduce emissions immediately
- Avoid multi-year construction timelines
- Minimize upfront capital expenditure
- Meet compliance requirements while infrastructure upgrades are underway
This flexibility makes capture technology especially relevant in emerging markets and smaller terminals.
Are capture and control systems effective?
Yes. STAX’s capture and control system has been third-party tested to show that it can remove up to 99% of PM and 95% of NOx. Ports and vessel operators can embrace solutions like emissions capture and control—enabling sustainable operations without compromising productivity or uptime—to prepare for future emissions regulations.
- Compared to shore power, STAX captures 12% more pollution when used with containerships, and 4% more when used with ro-ros. It also captures boiler emissions, which shore power does not.
- Approved by CARB to service all major vessel classes—including container, auto carrier (ro-ro), and tanker vessels—STAX currently operates the largest CARB-authorized fleet capacity for at-berth emissions control.
Why is STAX focused on pollution capture and not carbon capture?
STAX is meeting a pressing and long-standing need to remove pollutants from the air that are harming people’s health today. When people inhale polluted air, particulates embed in their lungs and bloodstreams, causing a variety of problems.
Communities near these ports, often marginalized populations, are particularly vulnerable. CARB has implemented strict emissions regulations targeting these pollutants, achieving an impressive 80% reduction in harmful emissions to date.
However, carbon capture represents the next frontier in tackling shipping emissions. Carbon dioxide (CO2) is a leading cause of global warming. The United States, the European Union, and Japan are heavily investing in Carbon Capture and Storage (CCS) systems, which are advanced technologies designed to capture CO2 for future use or safe storage.
As a recipient of a CARB technology grant, STAX is actively working on modifying and upgrading its system to capture carbon. In the spring of 2025, STAX, in partnership with Seabound, performed a comprehensive emissions and carbon capture test at the Port of Long Beach. The project showcased the first fully integrated emissions and carbon capture system for docked cargo ships, achieving removal rates of up to 99% of PM, 95% of NOx, 90% of sulfur, and 98% of CO2.
Where is STAX capture and control technology available?
STAX is currently servicing ports in California, including:
- The Port of Long Beach
- The Port of Los Angeles
- The Port of Oakland
- The Port of Hueneme
- The Port of Benicia
Emissions capture and control will soon be expanding outside of California. STAX is actively working to operate internationally, with a potential £38 million investment to deploy emissions capture and control technology across UK ports.
Schedule a Call with STAX
In 2025 alone, STAX treated 1,670 at-berth vessels and controlled 240 tons of pollutants. Schedule a call with our team to learn more about how we can help treat your vessel’s emissions while at berth.
