Selective Catalytic Reduction (SCR) systems for marine vessels

SCR technology is a cost efficient proven system capable of meeting (and exceeding) the regulatory requirements set for marine diesel engines operating in ECAs

SCR technology reduces the level of nitrogen oxides (NOx) with the use of a catalyst. It is compact, proven and is commonly used in land-based engines (eg heavy-duty vehicles, industrial plants and other applications). SCR technology can achieve over 98% NOx reduction in combustion processes.

Over 1300 NOxCare Marine SCR Systems Installed Worldwide

Our proven NOxCare Marine SCR Technology is already in operation in ships around the world. NOxCare Marine SCR systems are designed to be effective, robust, compact and easy to operate. Whether planning a new build or retrofitting an existing ship, our experts can help you ensure your ship complies with shipping environmental regulations. 

Yara is a leader in the design and installation of SCR technology for NOx reduction in maritime applications. Yara’s core NOx reduction know-how has been reinforced in recent years following acquisitions of Yarwil’s SCR activities and that of H+H Umwelt- und Industrietechnik GbmH also.

For more general information about the acceptance of Marine SCR Technology, visit the IACCSEA website.

NOx Reduction benefits of the NOxCare SCR system

Further benefits of reducing NOx emissions using the NOxCare SCR system:

  • Type approved NOx analyser is provided per engine, with continuous monitoring to control the cleaning efficiency of the catalyst and provide data for emission reporting 
  • An emission reporting module in accordance with IMO's NOx Technical Code (NTC 2008) can also be supplied 
  • The sensor is small, robust and easily replaceable. It can be installed directly on the stack, together with the analyser, avoiding unnecessary use of excessive gas piping for sampling
  • Small units save installation space
  • Applicable to all vessel types
  • Compatible for both new builds and retrofits 
  • The system is extremely robust 
  • Small control units and NOx analyzers save installation space 
  • The user friendly system ensures easy operation and maintenance 
  • Service packages tailored according to customer needs 
  • To save space the silencer can be integrated as part of the catalyst housing
Specially designed injector unit

Specially designed injector unit which produces a fine mist of urea droplets with minimal air consumption

Need a marine SCR system and urea solution to reduce your NOx emissions? 

Our NOxCare Marine brand is a complete NOx control solution specifically for our shipping clients. NOxCare Marine includes:

  1. Marine engine SCR design, construction and installation 
  2. NOxCare 40 Marine: Yara’s high-purity, specially developed urea solution for use as a marine SCR NOx reduction reagent 
  3. Service and spare-parts: delivery, spare parts, maintenance and technical support to help maintain your marine vessel’s SCR system and ensure optimal operation performance 

Read more on NOxCare 40 Marine (AUS40), our NOx reduction reagent for marine engine SCR systems 

Contact our NOx control experts today for Marine SCR systems, NOxCare 40 Marine or additional NOx Reduction services.

How Selective Catalytic Reduction (SCR) works in a maritime vessel

NOx is reduced using a catalyst together with NOxCare 40 Marine, a high purity urea solution. 

  • Exhaust gas passes through the catalyst, where the NOx is converted into harmless nitrogen and water 
  • Over 98% NOx reduction can be achieved – ie approaching zero emissions of NOx 
  • No increase in fuel consumption or CO2 emissions
NOxCare Marine – How SCR works

NOxCare Marine – How SCR works

NOxCare SCR Marine 

  • Is installed between the engine and the funnel (on some engines, typically large 2-stroke engines, it is installed before the turbocharger) 
  • Varies in size dependent on engine size and NOx reduction requirements
  • Can be tailored to match the layout of most engine rooms and casings 
  • Can replace existing silencers on retrofits with specially designed integrated SCR/Silencer units to accommodate space restrictions
  • Requires the vessel to be fitted with tanks for storage of NOxCare 40 Marine urea solution

NOxCare Marine is the only complete product offer which covers all your NOx reduction requirements through global availability of NOxCare SCR, NOxCare 40 urea solution and our global network of NOxCare Marine service engineers.

NOxCare Marine: 

  • Offers a cost efficient and effective alternative
  • Training ensures optimal operation performance
  • On-call experts will keep your system running smoothly 
  • Results in lower operational costs

SCR systems and Reagents (Reducing Agents)

SCR technology in marine vessels requires a specific urea solution (urea solution 40%, also known as AUS40) to function and reduce NOx emissions. Yara can supply a quality reagent, produced to Yara’s high quality standards, anywhere in the world. 

Read more about the availability of NOxCare 40 Marine, Yara’s urea reducing agent (AUS40) for use with Marine SCR.

How does the marine SCR system work with marine urea solution (AUS40)?

  • The SCR system is usually installed between the engine and the exhaust outlet, in some cases also pre-turbo
  • Urea solution 40% is injected into the SCR system 
  • The exhaust gases pass through the SCR catalyst 
  • A chemical conversion takes place between the reagent and the NOx gases 
  • The NOx is converted into harmless nitrogen and water and emitted to the atmosphere


NOxCare 40 Marine is sprayed into the exhaust gas, upstream of the catalyst where it is converted to ammonia. The ammonia mixes with the exhaust gas and reacts with the NOx molecules on the catalyst surface and form harmless nitrogen gas (N2) and water (H2O).


NOx reduction chemical reaction