Most of the actual industrial research efforts are aimed at reducing environmental burdens associated with human activities in the context of sustainable development. This trend has become increasingly prevalent in the naval transportation sector shown by a growing number of scientific publications dealing with life cycle assessments of maritime-related activities. However, the life cycle assessment framework provides practitioners with a variety of alternatives for conducting the analyses, giving room for defining key factors, such as functional units, system boundaries, and impact assessment methods, among others. This lack of standardization resulted in a wide range of assumptions and findings that are seldom comparable. The goal of this review is providing a systematic literature analysis, focusing on the characteristics of life cycle assessments dealing with the environmental impacts of various maritime vessel categories. In the first part, a qualitative analysis of the available scientific literature has been performed, providing a bibliometric analysis and a general overview of the characteristics of the studies (i.e., life cycle impact assessment methodologies, background data, and software tools used). The outcomes of the bibliometric analysis are then summarized and discussed to understand current practices and future trends in this field, providing the basis for the normalization phase of the results. The second section of the paper offers advice for naval practitioners on how to perform results normalization to produce comparable analyses. Two approaches for normalization have been proposed in the frame of this study: an “horizontal” one, which is based on vessel features and allows a comparison among different vessel typologies, and a “vertical” one that enables to fairly compare vessels of the same category to one another. In addition, each section reports the outcomes of greenhouse gas-related impact categories, which have been subjected to the proposed normalization procedure, along with the order of magnitude of the results for each life cycle phase. The overall work provides an overview of LCA impact results as well as a collection of procedures and recommendations for future life cycle assessments based on specific vessel types, in terms of functional unit selection, system boundary definition, impact assessment approach, presentation of the outcomes, and normalization basis.

大多数实际的工业研究工作旨在减少与可持续发展背景下的人类活动相关的环境负担。这种趋势在海军运输部门越来越普遍，越来越多的科学出版物涉及海事相关活动的生命周期评估。然而，生命周期评估框架为从业者提供了多种进行分析的替代方案，为定义关键因素提供了空间，例如功能单元、系统边界和影响评估方法等。这种缺乏标准化导致了广泛的假设和发现，这些假设和发现很少具有可比性。本综述的目的是提供系统的文献分析，重点关注生命周期评估的特征，以应对各种海上船舶类别的环境影响。在第一部分，对现有科学文献进行了定性分析，提供了文献计量分析和研究特征的一般概述（即生命周期影响评估方法、背景数据和使用的软件工具）。然后对文献计量分析的结果进行总结和讨论，以了解该领域的当前实践和未来趋势，为结果的标准化阶段提供基础。本文的第二部分为海军从业人员提供了有关如何执行结果标准化以产生可比分析的建议。在本研究的框架中提出了两种标准化方法：一种是“水平”方法，它基于血管特征并允许在不同血管类型之间进行比较，另一种是“垂直”方法，可以公平地比较相同的血管类别相互。此外，每个部分都报告了与温室气体相关的影响类别的结果，这些影响类别已经过拟议的标准化程序，以及每个生命周期阶段的结果的数量级。总体工作提供了 LCA 影响结果的概述以及一系列程序和建议，用于基于特定船舶类型的未来生命周期评估，包括功能单元选择、系统边界定义、影响评估方法、结果呈现、和标准化的基础。