# Multicriteria Analysis of Alternative Marine Fuels in Sustainable Coastal Marine Traffic
## 4 Application and Analysis of the Results
### Application of Multicriteria Approach for Alternative Fuel Selection  
The alternative fuel selection problem is represented in a hierarchical form with four levels, in order to facilitate the structure of the problem. We propose a hierarchical structure (Figure 4) starting with the main goal at the top--that being the achievement of sustainable marine coastal traffic. The main goal is supported by three objectives that need to be accomplished in order to achieve such a goal. In this way, we managed to reduce the degree of the complexity in the further analyses by separating the main goal and particular objectives. Those objectives are (a) \"maximization of environmental aspects\", (b) \"maximization of technological aspects\", and (c) \"maximization of economic aspects\".  
Each of the three objectives is divided into supporting or sub-objectives, representing criteria for evaluation of the alternatives. Objective (a) is supported by three sub-objectives, objective (b) by four sub-objectives, and objective (c) by three sub-objectives. Alternatives are placed at the bottom of the structure and they are connected to all criteria groups, meaning that their evaluation considers the maximum utilization of all objectives.  
The criteria chosen for the analysis consider the environmental, technological, and economic aspects. Each selected aspect consists of several criteria (shown in Table 3) and is further evaluated by the stakeholders. The selection of these particular criteria, however, was based on the combination of similar research [16; 25; 41; 43] and discussion with stakeholders. The result is 10 criteria in total (three are related to environmental, four to technological, and three to economic aspects). The environmental criteria consider climate change impact from marine coastal traffic through global warming potential, acidification of the sea due to CO\({}_{2}\) dissolvement, and exhaust emissions considering the air quality in the vicinity of marine transport routes and potential health impact. The technological criteria consider the existence and availability of alternative fuel-related infrastructure, the reliability of fuel supply, possibility and requirements for adaptation of ship engines to alternative fuel, and the safety of the alternative in terms of general use. The economic criteria consider the required investment size due to new technological requirements, operational costs considering the requirement for possible additional personnel or crew, maintenance or insurance policies, and the last criterion is the fuel purchase price.  
Following the hierarchical scheme presented in Figure 4, the importance of each main objective is evaluated followed by the evaluation of the sub-objectives or criteria. The evaluation is based on a questionnaire that was presented to each stakeholder and their task was to estimate the relative importance of each element within every group. A comparison matrix was created based on the pairwise comparison data, and the overall criteria weights were determined based on the AHP methodology.  
In the second part of the evaluation, stakeholders evaluated the performance of each alternative in relation to every sub-objective or criterion. Alternatives are selected according to Act on the establishment of alternative fuel infrastructure [13]. The evaluation of the performance is based on the stakeholders' knowledge, opinions, and experience. The performance of all criteria was evaluated on an absolute scale and using the SAW approach the results were normalized and implemented into the final ranking results.  
Figure 4: Hierarchical structure of the alternative fuel selection problem.