The International Maritime Organization (IMO) and European Union (EU) have set targets to reduce greenhouse gas (GHG) emissions. Focusing on ships above 5000 GT, their measures exclude several ship types, such as fishing vessels, offshore ships, and yachts. However, smaller ships generate 15–20% of the total GHG emissions. Multiple potential fuel alternatives are already in use or have been investigated to minimize carbon emissions for coastal ferries. This study evaluates the possibility of using alternative fuels for small ferries by seven different parameters: technical readiness, presence of regulations, GHG emission reduction effectiveness (with two different criteria), capital expenditure (Capex), operating expenditure (Opex), and ice navigation ability. The assessment is based on an evaluation of state-of-the-art literature as well as second-hand statistics and press releases. The study also reports the most recent implementations in each alternative technology area. As a result, it was found that although there are several measures with high potential for the future, the most feasible fuel alternatives for coastal ferries would be fully electric or diesel-electric hybrid solutions.

Global, regional and national policies and regulations are providing incentives to reduce greenhouse gas (GHG) emissions in ports, and the first step in this effort is to obtain a detailed overview of the main sources of emissions. The rapid developments in port GHG mapping have led to the need for a case study to assess the effectiveness and practical use of these methodologies and to suggest best practices for ports just starting this mapping process. Here, we present the current state of the art in the assessment of GHG emissions in ports. This analysis enabled us to identify the most promising methodologies to assess GHG emissions in ports in an efficient, reliable and near real-time manner. We then tested the best methodologies and practices that emerged from the review articles to build a GHG assessment system in the Port of Tallinn. Finally, we assess the advantages and disadvantages of current approaches and suggest promising ways forward.

The maritime sector aims to achieve carbon neutrality by 2050. Consequently, shipping companies are investigating efficient and optimal ways to minimize greenhouse gas emissions. One of these measures includes vessels that operate on alternative non-carbon fuels. In this study, we compared a diesel-fuelled catamaran’s greenhouse gas (GHG) emissions and its fully electric sister vessel, which operates on the same line. This study showed that the GHG emissions of the electric vessel were only 25% of those of its diesel-powered sister vessel. However, this figure highly depends on the source of electricity in the operating country. In this case, the energy cost of the fully electric vessel was 31% cheaper than the cost of diesel energy and the payback time without possible subsidy for replacing a diesel ferry with an electric one would be 17 years and 6 months. We also showed that the additional energy from solar panels sufficiently covers several application options for consumers even in winter, when there is low solar energy production. This study brings more insight into the academic literature on decreasing maritime CO₂ emissions from city water traffic. Regarding its managerial implications, our study findings can be used when shipping companies evaluate options for reducing their emissions. The results of this study show that using fully electric vessels has major benefits not only concerning carbon emissions but also financially.