EMISSIONS: Lower fuel consumption leads to less emissions
Cleaning exhaust gasses before they escape the funnel is a way to reduce emissions. However, the reduction of NOx and CO2 emissions should start before this: by burning less fuel.
There are several ways to reduce fuel consumption. New, innovative hull designs with low resistance have been developed, and much effort has been put into improving the efficiency of diesel engines and turbines.
Still, a considerable further reduction in fuel consumption can be achieved by improving the efficiency of the propulsion system.
Higher propulsive efficiency leads to a less installed propulsion power, and the engines can be smaller.
Less propulsion power leads to lower fuel consumption (reduced fuel bunkers / larger range). Lower fuel consumption leads to a reduction in emissions (smaller exhaust treatment systems).
Besides saving the environment, less emissions mean other key benefits, one being lower fuel bills.