In the thesis report below a cost benefit analysis of the OCCS system is going to be performed for two categories of vessels, tankers and bulkers. The cost benefit analysis will take place in two scenarios. In the first the 2-tier levy proposed from IMO will not be implemented. In the second scenario the 2-tier levy will be implemented. The goal of this thesis is to research the conditions, in both scenarios, upon which this system will create an ROI beneath 10 years making this installation a sound investment for a company.