Marine shipping, which is considered as the backbone of international trade, predominantly relies upon dirty fossil fuels for its operation. Tougher regional and global environmental regulations are now challenging the industry to take action – in line with the Paris Agreement goals. In the form of three research papers (two published and one conference paper), this thesis quantifies environmental benefits and financial costs of switching to cleaner alternative technologies. Hence, providing a “guiding tool” for policymakers for implementing best-case practices within the industry. Owing to its maritime dependency, proven vulnerability to shipping emissions and its reluctance for compliance with the established regulations, Ireland was selected as the research case study. Paper-1 investigated the NPV of Shore Side Electricity (SSE) adoption utilising the existing (2019) and future (2030) Irish energy mix. The future electricity supply is anticipated to be “cleaner” due to an increase in the uptake of renewable energy sources, which is expected to boost the present (2019) NPVs. The paper finds that cost-effectiveness will be higher if the ten most frequently visiting ships switch to shore side power. Paper-2 estimated and compared the NPV of three blended biofuels (FAME, HVO and FT-Diesel), against the relatively popular options of scrubbers and low-sulphur oil, used to mitigate pollutants. To comply with the proposed Atlantic-ECA regulation, blended FAME was found to be the most cost-effective option using NPV. Paper-3 analysed the NPV of four low-carbon marine fuel technologies: LNG, Methanol, Green Hydrogen, and Green Ammonia. LNG had the highest NPV, followed by methanol and hydrogen, with ammonia showing a negative NPV, due to high operational costs. To meet the future decarbonization targets, Green Hydrogen will be the most suitable alternative over LNG and methanol respectively. The three papers in this thesis combine to provide a range of policy initiatives for the Irish government to contemplate while developing its maritime action plan. Ireland needs to consider how it can rapidly progress to meet the near- and long-term emission goals and how it can influence other partners to do so. This thesis provides clear evidence about practicality of different green technologies, to help the government make informed decisions.