This study evaluates parametrically various emission reduction methods considering the IMO carbon emission constraints for 2030, 2040, and 2050. It proposes an onboard aftertreatment CCS in conjunction with different AFs to assess their potential for carbon reduction. The study calculates values for carbon factors and specific fuel consumption based on the resulting emissions. Additionally, the parametric analysis uses projected total fleet sizes and estimated carbon emissions across short, medium, and long-term time frames. The findings of the study demonstrate a surge in the utilisation of AFs, with LNG leading its position as the predominant AF, projected to account for a range of 10 %-30 % by the year 2030. Zero-carbon fuels like hydrogen and ammonia and CCS applications, providing approximately 95 % CO2 reduction for each fuel, are expected to aid in meeting 2030 targets, though widespread adoption is not forecasted. Stricter 2040 targets will require the utilisation of carbon-neutral and low-carbon fuels integrated with CCS, which constitute 60 %-80 % of marine fuels. By 2050, hydrogen and ammonia with rates exceeding 60 % are projected to surpass conventional fuels; however, if zero-carbon or AFs do not dominate, CCS technologies must be universally implemented to meet emissions targets.