In 2020, the industrial sector remained the largest emitter of GHGs, accounting for 31% of worldwide GHG emissions. The electric power industry contributed 28% of the worldwide emissions, with coal burning accounting for the great majority. Figure 1, based on the Rhodium Groups report, shows an independent research provider combining economic data in the United States. The information displays that the combined emissions from land use, agriculture, and garbage accounted for 18% of the global total, followed by transportation at 16% (land transport at 12%, maritime transport at 3%, and aviation at 1%) and buildings at 7% [1].

In coastal regions, seaports are among the most essential industrial zones. They consume a tremendous amount of electricity for industrial purposes, the majority of which is derived from fossil fuels that are responsible for 20% of global GHG emissions, contribute to the majority of maritime transport types that are responsible for 2.5% of global GHG emissions, and have numerous buildings for their official and industrial functions that can contribute to produce 1% and 9% of global GHG emissions, respectively, according to Figure 1.

The International Maritime Organisation (IMO) challenged the shipping industry to reduce yearly GHG emissions by 2050 to at least 50% of the 2008 levels. According to the fourth IMO GHG study in which 2008 was set as a baseline, maritime GHG emissions will likely increase by 90–130% by 2050 without significant decarbonisation. To achieve zero emissions, the shipping industry must act promptly and cooperatively and take comprehensive measures from multiple perspectives to counter the adverse effects of global warming [2].

The maritime industry relies greatly on fossil fuels. It emitted around 3% of the global GHG emissions in 2020 or approximately 1.2 gigaton equivalents of carbon dioxide (CO_2eq); this value exceeds the emissions of the world’s fifth largest GHG-emitting country [3].

The fact that 70% of ship emissions occur within 400 km of coastlines demonstrates that all of the most polluting cities in the world are located along coasts [4]. Therefore, ports, as intersecting points for marine and other modes of transportation, can play a critical role in mitigating global climate change. Moreover, the carbon dioxide emissions generated by various activities conducted at ports are one of the most significant environmental features of ports that contribute to the problem of climate change.

Hence, shifting the operations and practices at a port toward sustainability is recognised as an essential goal in several SDGs. For example, goal 7 acknowledges that all ports have a high potential for generating power from renewable energies because of their proximity to the wind, direct sunlight, and marine environment; goal 9 focuses on industry, innovation, and infrastructure; goal 11 recognises that ports are now located within cities and are part of smart cities, and goal 13 focuses on the climate change issues [5].

Notably, global societies created specific global standards, such as the Maritime Pollution Regulation (MARPOL) Annexe IV of the IMO (released in 2005 and last revised in 2022) [6], the ‘Carbon Footprinting Guidance for Ports’ issued by the World Ports Climate Initiative (WPCI) in 2008 [7], and the ‘European green deal’ by European Sea Ports Organisation in 2020 [8]. Some of these standards can be considered international community actions to reduce carbon emissions at ports.

Considering the significance of CF reduction metrics in ports, particularly for clarifying standards, guidelines, normativity, key concepts, and best practices, this reviesearch aw study aims to identify and categorise the most recent measures, actions, projects, and guidelines to reduce the carbon footprint (CF) in seaports, which are significant hubs for commerce and transportation.

2. Energy Management System

The viability of using intelligent energy systems in residential and commercial construction increased with the recent promise of information and communication technology (ICT) applications for fabrications, construction, and building automation networks. The global energy needs are expected to rise in the coming decades because of the projected population growth and potential industrial expansion. This topic focuses on increasing public knowledge of the environmental effects of energy production, delivery, and consumption. Considering the preceding points, the critical challenge for an EMS is to reduce environmental consequences while maintaining the quality and influence of energy prices ^[9][12]. A modern EMS for marine ports also offers creative, efficient, safe, and cost-effective seaport options. This system involves energy generation from all resources, including renewable sources, etc., energy distribution, and energy consumption control. At a port, energy generation refers to activities that convert fossil fuel and renewable energies, such as wind, solar, and wave energies, into electricity. In contrast, energy distribution refers to the systematic and intelligent distribution of energy to users. Using electricity for ports and port-related tasks, such as cargo handling, industrial operations, logistics, and office tasks, is energy consumption. According to an economist intelligence assessments report, by 2032, fossil fuels will still constitute 78% of the global energy mix, which is only a modest decrease from 81% in 2022 ^[10][13]. Furthermore, ports are frequently located in areas that are particularly well-suited for power generation from renewable energy sources such as wind, sun, and waves (such as Rotterdam in the Netherlands and Kitakyushu in Japan) and tide differentials (which are currently being researched, for example, in Dover, the UK, and the Port of Digby, Nova Scotia). In some cases, geothermal energy presents an opportunity to move toward greener energy, as in the case of Hamburg port. Additionally, broad, flat surfaces such as storage areas and warehouses that can be used for solar panel installation are frequently found in ports (e.g., the Tokyo Ohi Terminal or the Port of San Diego administration buildings). However, seaport energy management necessitates policies, technological developments, and operational measures. Therefore, achieving EMS goals lies at the heart of national and international EMS rules and regulations in marine ports ^[11][14]. Hence, several laws governing the use of the EMS are being passed worldwide. Some of the significant international policies are as follows:

• Energy Management, ISO 50001 ^[12][15];
• Energy Management Systems, EN 16001 ^[13][16];

• Plans for Managing Port energy (PeMP);
• Environmental Management Systems Address Energy Management (EMS);
• Green Port Policies and Port Environmental Management Plans (PEMP).

Furthermore, following the implementation of an EMS in a seaport, the following areas must be covered by technological and operational steps to improve its performance:

• Classification of port-related activities (direct and indirect or land-based and maritime-based);
• Important operational metrics;

• Primary technological solutions for vehicles and equipment at ports and terminals;
• Energy saving port structures;
• Additional facilities and infrastructure to support port energy efficiency.

Nowadays, an EMS may be considered a component of the distributed energy resources (DER) programme, which is defined as ‘energy-producing services that are directly connected to medium voltage or low voltage delivery grids rather than bulk energy broadcasting systems’ ^[9][12]. Through the DER, the components of EMS can be divided into eight primary categories: (i) intelligent network, (ii) virtual plant, (iii) ICT, (iv) Internet of Things (IoT), (v) microgrids, (vi) artificial intelligence (AI), (vii) distribution of production, and (viii) renewable energies. An intelligent network employs microgrids and virtual power plants (VPPs) as hardware and ICT, IoT, and AI as software to support efficient product distribution. It leads to a new perspective that controls energy use through DER. For all procedures, the use of renewable energy rather than fossil fuels was essential, especially given the growing threat of global warming and climate change. All the components, which include software and hardware, operate with an intelligent control system to form an intelligent network.

3. Infrastructure and Equipment

The second component of the carbon reduction measures in seaports is related to the infrastructure and equipment utilised to reduce directly or indirectly reduce the CF of the ports. The categorisation in this section is based on numerous aspects and approaches. The two main categories are as follows: (i) creating new or developing current infrastructure, and (ii) CF mitigation equipment and tools and installations in seaports that use cutting-edge technologies with high efficiencies, resulting in reduced energy use and a smaller CF. All the studies discussed here are classified accordingly into these two groups (see Table 1). In some cases, these infrastructures, tools, and installations were already in place and were simply updated, whereas in others, they were built from scratch: Note that some infrastructure and equipment already exist and should be ecologically friendly and upgraded before attempting to build new ones. However, for the use of new infrastructures, tools, and applications, as well as for the implementation of legislation, the rules and policies, are required.

4. Guidelines and Regulations

Owing to the 7th, 9th, 11th, and 13th goal of SDGs, green ports became especially important; these goals are related in order to obtain affordable, clean, and sustainable energy; sustainable industries; innovation and infrastructures and sustainable cities; and climate change mitigation [5]. On the other hand, the concept of a ‘green port’ is closely related to environmental integration and states that the port’s management and operations should all be in harmony with the environment ^[30][51]. The measures taken to realise green ports can be classified based on several criteria, such as the use of EMS, CI, and so on, to minimise carbon emissions during port activities. However, all these actions necessitate the implementation of specific mandatory criteria for all involved parties. The third section of seaport CO₂ reduction actions in this researchtudy states that enacting appropriate laws, standards, and regulations enables the applicable policies to connect the equipment and facilities with energy management in all stages of generation, distribution, and consumption.