# Port-Related Shipping Gas Emissions--A Systematic Review of Research
## 3 Discussion and Results
### Analysis of the Most Commonly Applied Methodologies and Datasets--Third Layer
#### 3.3.5 EEA Research  
General guidance for the control of ship emissions in the EU has been provided by the European Environment Agency (EEA) through the EEE 20 Guidebook, Section 1. A.3.d. [85]. The key function of the EEA 20 Guidebook is to offer estimation methods and emission factors for developing inventories at various levels of sophistication that are transparent, consistent, complete and comparable [85]. Guidelines of different complexities for calculating ship-sourced gas emissions are incorporated in its three-tier system. The less data-demanding Tier 1 and Tier 2 approaches use fuel sales as the primary activity indicator and assume average vessel emission characteristics to calculate emissions estimates. The Tier 3 methodology is based on ship movement information for individual ships and requires detailed ship motion activity data, as well as technical information about ships [16]. The practical aspect of the Tier 1 and Tier 2 approaches is that they require less detailed data and are better suited for quantifying gas emissions at the national level, while the Tier 3 activity-based level can provide detailed site-specific results. For this reason, the Tier 3 methodology, applicable to port areas, is conceptualised in FB Equation (9) and EB Equation (10) [16]. \[\mathrm{E_{Trip,i,j,m}}=\sum_{\mathrm{P}}\left(\mathrm{FC_{j,m,p}}\times \mathrm{EF_{ij,m,p}}\right) \tag{9}\]  
\[\mathrm{E_{Trip,i,j,m}}=\sum_{\mathrm{P}}\left[\mathrm{T_{P}}\sum_{\mathrm{e}} (\mathrm{P_{e}}\times\mathrm{LF_{e}}\times\mathrm{EF_{ij,j,m,p}})\right. \tag{10}\]  
where:  
\(\mathrm{E_{Trip}}\): Emission over a complete trip--in metric tonnes (t);  
FC: Fuel consumption--in metric tonnes (t);  
EF: Emission factors of different pollutants in regard to engine category, engine type, fuel type, activity mode--in kilograms per ton of fuel (g/t) or grams per kilowatt hour (g/kWh);  
i: Pollutant;  
m: Fuel type;  
j: Engine type;  
p: The different phase of trip (activity);  
LF: Average load factor of engine at berth/manoeuvring--as a percentage of engine power (%);  
P: Engine nominal power--in kilowatts (kW);  
T: Average time spent in phase of trip (activity)--in hours (h);  
e: Engine category. Comparative Analysis of Key Components and Proposition of Relevant Methodology for Estimation of Ship Emissions in Ports--Fourth Layer  
After reviewing the selected studies, it was concluded that the general methodologies for estimating ship emissions in ports are based on a combination of data about ship engines, fuel consumed and movements, along with their effects on engine performance and EFs based on energy consumption. Depending on their complexity, all of the aforementioned factors contain several key components that, by interacting with each other, largely determine the amount of gas emissions from the ship. The key components, that is, the data that define them, can be considered static and dynamic. The static data on particulars of the ships and their engines describe components for emission calculations, such as engine power (EP), engine function, engine type and fuel type. It can therefore be said that TD can be described as static while MA can be considered dynamic data. Ship MA is categorised by the operational mode of the ship's propulsion system and defined by dynamic information on the percentage of ME and AE working load expressed as LF. Since different activities do not have the same impacts on emissions, it is equally important to consider the time spent in each operational mode. Finally, as the central and most complex segment of the emissions quantification process, EF depends on both static data about engine function, engine type and fuel type and dynamic information about the characteristics of the ship's activities. Throughout the analysis of the studies, it was also found that mainly a combination of maritime traffic statistics from local or national maritime organisations and AIS informationwas used in data collection.