# Comparative Analysis of Marine Alternative Fuels for Offshore Supply Vessels
###### Abstract
However, hydrogen faces significant challenges in storage and transportation due to its low energy density and need for cryogenic or high-pressure storage [5]. Ammonia, while offering the potential for zero-carbon emissions at the point of use, poses safety concerns due to its toxicity, as well as technical challenges related to combustion and storage [6]. Methanol is gaining attention as a cleaner alternative fuel, particularly because of its simpler storage and handling compared to LNG and hydrogen [7]. It is highlighted in studies for its ability to reduce SOx and NOx emissions and its adaptability to existing engine designs with minor modifications. However, methanol's lower energy density compared to conventional fuels means larger fuel tanks are required, which poses logistical challenges, particularly for space-constrained vessels. Biodiesel, derived from renewable sources such as vegetable oils and animal fats, is considered a near-term alternative that can be used with minimal engine modifications [8]. On the other hand, biodiesel's scalability and its potential to increase NOx emissions are critical concerns, which limit its long-term viability for widespread adoption in the shipping sector [9]. [PERSON], [PERSON] [10] (p. 100033) points to the crucial role of regulatory frameworks in driving the adoption of alternative fuels. Studies on policy impacts indicate that strong international regulations, such as the International Maritime Organization's (IMO) 2030 and 2050 emissions targets, are key drivers for fuel transition. The adoption of market-based measures such as carbon pricing is identified as an essential tool to incentivise the shift to alternative fuels [11]. In conclusion, while significant research has been conducted on alternative marine fuels, it is clear that each fuel option presents its own set of advantages and limitations. Fuels like LNG reduce emissions short-term but face challenges like methane slip, while hydrogen and ammonia offer long-term potential with technical barriers. Methanol and biodiesel also have trade-offs. A multi-criteria decision-making approach is crucial to evaluate environmental, technical, and economic factors for optimal fuel selection in maritime decarbonisation. In terms of decision-making processes, multi-criteria decision-making (MCDM) approaches are frequently mentioned. These frameworks allow for the evaluation of multiple factors, including cost, environmental impact, fuel availability, and regulatory compliance, to support strategic decision making in the selection of marine fuels [12]. Several studies consistently highlight the importance of integrating sustainability criteria alongside economic and operational considerations to ensure the most effective fuel transition for various vessel types and operational profiles [13]. Several studies have applied MCDM approaches to assess the viability of various alternative fuels in the maritime sector. For example, [PERSON], [PERSON] [14] (p. 2600) utilised the AHP method to rank alternative fuels based on environmental, economic, and technical criteria. Similarly, [PERSON], [PERSON] [14] (p. 2600) applied the TOPSIS method to evaluate the most sustainable fuels by considering emissions reduction, cost, infrastructure requirements, and safety. Their findings emphasised the difficulty in balancing environmental performance with economic and technical feasibility. For instance, although hydrogen emerged as an ideal candidate for zero-emission shipping, the costs associated with its production, storage, and transportation were prohibitive when considering current technological capabilities. [PERSON], [PERSON] [12] (p. 7498) applies the TOPSIS and AHP methods to assess LNG and hydrogen for maritime use, incorporating uncertainty into the evaluation process. This highlights the difficulty of weighing short-term benefits (like LNG's maturity) against long-term environmental impacts (hydrogen's zero-emission potential).