# Economic Feasibility of Retrofitting an Ageing Ship to Improve the Environmental Footprint
## 1 Introduction
Comparison employing the Life Cycle Assessment (LCA) of specific ships operating in a particular area may show an advantage when using one or another fuel. This way, a feeder container ship and a passenger ferry operating between Mainland China and Taiwan are compared [19]. For both ships, two scenarios are considered with HFO and LNG as fuel. The study indicated possible improvement in total fuel-life cycle GHG emissions from using LNG. The reduction in the emissions of NO\({}_{x}\) is (38-39%) and CO (42-43%). Remarkable reduction is obtained using LNG in SO\({}_{2}\) (99.8%) and \(PM_{10}\) (97.5%), while methane emissions increase significantly when LNG is used as an alternative fuel for both ships. Comparative studies also appear with the continuous improvement of technologies to produce alternative fuels. A recently presented study [20] compares seven alternative marine fuels--LNG, liquefied biogas (LBG), methanol from natural gas, renewable methanol, hydrogen for fuel cells produced from (1) natural gas or (2) electrolysis based on renewable electricity, and Hydrotreated Vegetable Oil (HVO), and HFO. Ten performance criteria rank the marine fuels and different stakeholder groups set their relative importance in Sweden. The criteria include economic, environmental, technical and social aspects. Economic criteria are the most important for ship owners, fuel producers and engine manufacturers, while the Swedish government authorities prioritise environmental criteria, specifically GHG emissions. Based on the views of the first group members, LNG is ranked the highest, with HFO second, then the fossil methanol, followed by biofuels. For the second group of stakeholders, hydrogen is ranked highest, followed by renewable methanol and HVO. The Getting to Zero Coalition [21] is an alliance of more than 200 companies and organisations from the maritime, energy, infrastructure and financial sectors, supported by governments and international organisations. The goal of the coalition is to bring into operation commercial alternative fuels with zero emissions by 2030, leading to the complete decarbonisation of maritime transport by 2050. To achieve this goal, an S-curve has been defined [22] according to which, by 2030, scalable zero-emission fuels (SZEF) as hydrogen and hydrogen-derived fuels, such as ammonia, e-methanol and synthetic hydrocarbon, should be 5% of all fuels used, 27% of all fuel used by 2036 and 93% of all fuel used by 2046. Such a pace is needed to meet the goal of the 2016 Paris climate agreement to limit global warming to well below 2, preferably to 1.5 degrees Celsius, compared to pre-industriallevels [23]. A major obstacle to achieving these goals is the significant price gap between fossil and zero-emission fuels. For example, the estimated production price (EUR/GJ) by 2025 of e-hydrogen, e-ammonia, e-methane and e-methanol is 6 to 7.3 times higher than that of LNG [24]. A summary of the use of alternative fuels as of 2022 was made by Det Norske Veritas [25]. Of the total gross tonnage of ships operating today, 5.5% use alternative fuels and one-third (33%) are on order and can work with alternative fuels. The report evaluates 24 scenarios for the maritime energy mix in 2050 among five groups: fossil fuels, biofuels, electro fuels, blue fuels and electricity. A preferred alternative fuel cannot be specified due to uncertainty about the availability of sufficient amounts of biomass for biofuels or sufficient renewable electricity for electric fuel production. In addition, considerable investments in this direction are needed in the coming decades, which are estimated at $8 billion (bn) USD to $28 bn USD annually in investment on ships in a transition phase towards decarbonisation in 2050 and about $28 bn USD to $90 USD bn per year for onshore to scale up production, fuel distribution and bunkering infrastructure to supply 100% carbon-neutral fuels by 2050 [25]. There is considerable research on alternative marine fuels' environmental and economic aspects.