The size of the sails / solar / wind turbine to replace this would be...? You get the idea.
As for carbon reduction, the engines already run at ~50% efficiency so there is little waste. The amount of carbon produced is the reality of pushing such a huge weight through the water.
I should have made it clearer in my post but I wasn't suggesting replacing diesel engines with Sail power, just augmenting it in the same manner as the SkySails (see response from jk4930 and markdown).
I also don't see why covering the deck in solar panels, or installing some form of wind turbine, wouldn't go some way to reducing the demand from diesel power generators.
In either case, I don't think you understand just how brutal the maritime environment is. A typical oceangoing ship has steel panels at main deck level dented in from the impact of the sea. I don't think solar panels are going to hold up so well.
Unless you can find a way for that wind turbine to both generate electricity and work as a "sail" so it propels the ship, it is just going to add drag that is counterproductive to the problem you're trying to solve.