Status: Need is Closed

Low Cost SOx and NOx elimination from Ship Exhaust

Request Number

Point of Contact
Need was closed on
Aug 7, 2018

We are seeking novel approaches to eliminate SOx and NOx emissions from ship engine exhaust as a way of satisfying Sulfur Emission Control Area requirements while burning high sulfur fuels. 


The ideal solution would be roughly half the total cost (capital and installation) of traditional closed-loop, in-line wet scrubber systems and easily retrofitted onto cargo ships and passenger/freight ferries currently operating in the Sulfur Emission Control Areas. 



The companies comprising the Swedish-based Stena Sphere represent one of the largest private shipping groups in the world. We are seeking solutions that can be applied to cargo and passenger ships that travel in all of the world’s oceans.


Historically, our ships run on a wide range of fuel types (with sulfur concentrations up to 3.5%) and under a wide range of engine operating conditions.  Recent changes to SECA fuel sulfur limits (from 3.5% to 0.1%) require us to either purchase costly low-sulfur fuel, or install SOx scrubbers to eliminate the equivalent amount of sulfur from our ship engine exhaust.


Stena has had good success recently using closed-loop, in-line wet scrubber systems.  However, the cost of these systems prevent rapid, broad adoption across our fleet operating in Sulfur Emission Control Areas.


Key barriers we have encountered in reducing the cost of installing scrubbers include:

  • Current open loop systems include many components, tanks, pumps, and associated piping spread across several compartments. This drives system complexity and higher installation costs.
  • The corrosive environment within the scrubber requires expensive materials of construction.
  • Scrubbers require large volume to provide sufficient contact time between the exhaust gas and wash water droplets.

Current systems require large volumes of sea water, requiring large pumps and piping. Closed loop systems require a cooling step using large volumes of sea water.  Open loop systems require large volumes of sea water to capture SOx from the exhaust gas.  


Key success Criteria
  1. Technical Viability-- Solutions proposed must be based on sound scientific principles and have laboratory or pilot scale data that demonstrate efficacy.
  2. Scale up Potential—Solutions proposed must have a clear pathway to be application on commercial ships within 1-2 years. Solutions already practiced in marine markets have higher value. The ideal partner would be able to lead the design and installation of full-scale systems.
  3. Costs—Solutions would need to provide reasonable return on investment, consistent with the anticipated annual savings of using high sulfur fuels in place of more costly low sulfur fuels.  
  4. Ownership—Solutions covered by patents have higher value. At a minimum, proposed solutions must not be prohibited by other patents in the field. 


Possible Approaches

We would consider novel designs for wet scrubber systems that are more compact, less complex, lower capital, or easier to install on existing vessels.    

  • Alternate locations for exhaust scrubbing outside the exhaust funnel (e.g., engine room)
  • Closed loop scrubbers that don’t require a wash water cooling step
  • Open loop scrubbers with wash water cleaning to meet anticipated future environmental limits (e.g., pH, turbidity, PAH)
  • Plug-and-play or single compartment designs


We would also consider emerging technologies for SOx and NOx reduction based on alternative modes of operation.

  • Dry absorption systems with manageable pressure drop and dry chemistry logistics
  • Cold plasma


Any solution would need to be consistent with the practical space limitations for installation in existing vessels, and would not require specialized skills or extensive training of operating personnel.


Approaches not of Interest

Open loop scrubbers that discharge directly into the sea.


Due Date
Jul 31, 2018
Items to be submitted

We are looking for concise, non-confidential proposals. The proposal should describe the technical approach and should ideally include information on the technological readiness of the proposal, any proof of concept data, reference to any peer reviewed publications, and potential route to commercialization.


Client Point of Contact

Super User
Alan Gordon
Gallery Moderator(s)
Oliver Worsfold
Request Number
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Area of Interest