Greenhouse Gas Emissions from Maritime Traffic

In this research, we follow a bottom-up approach to estimate greenhouse gas emissions from vessel journeys. The methodology is based on the Fourth International Maritime Organization (IMO) Greenhouse Gas Study (2020) and was adapted by Cherryl Chico. Vessel navigation data from Automatic Identification System (AIS), and vessel specification data from Ship Register database are used to calculate emissions for the Pacific Island Countries.

Methodology

Theoretical Foundation

Emissions are calculated for two groups of greenhouse gas (GHG): energy-based—nitrogen oxide (NO_x), methane (CH₄, carbon monoxide (CO), nitrous oxide (N₂O), particulate matter (PM₁₀,PM_2.5 ), and non-methane volatile organic compounds (NMVOCs), and fuel-based—carbon dioxide (CO₂) and sulphur oxides (SO_x).

Black carbon (BC) can either be energy- or fuel-based depending on the fuel type. Energy-based GHG is expressed as the product of emission factor and power demanded adjusted by a correction factor based on engine load (Eq. 1). For fuel-based GHG, power demanded is converted to specific fuel consumption. Emissions is calculated per hour and per engine (i.e. main engine, auxiliary engine, or boiler if available) of the vessel in operation.

(1)\[Energy{-}Based\ Emission_{GHG} = \sum_E \sum_i EF_{E,GHG} \cdot P_{E,i} \cdot LCF_{E,i,GHG}\]

(2)\[Energy{-}Based\ Emission_{GHG} = \sum_E \sum_i EF_{E,GHG} \cdot P_{E,i} \cdot LCF_{E,i,GHG}\]

Where

• \(E\) is the vessel’s engine

• \(i\) is hour

• \(EF_{E,GHG}\) is the energy-based emission factor (g/kWh) for engine \(E\) and gas \(GHG\)

• \(FF_{E,GHG}\) is the fuel-based emission factor (g/kg-fuel) per for engine E and gas GHG

• \(LLF_{E,i,GHG}\) is the low load adjustment factor for gas GHG given load at hour \(i\)

• \(P_{E,i}\) is the power demanded of engine \(E\) at hour \(i\)

• \(FC_{E,i}\) is the fuel consumption of engine \(E\) at hour \(i\)

Each of the components of equations (1) and (2) are collected data by the IMO from various literature and from their own calculations which are then reviewed per iteration of the GHG study. They are presented either as an equation, decision matrix, or reference table.

Power Demanded

Power demanded is the power required to operate a vessel at a given speed and displacement. In the GHG study, the power demanded by the main engine is a function of the vessel’s speed and draught at any given hour. Power demanded is expressed as the product of engine load and maximum power, where engine load is derived from the admiralty formula including correction factors (CF). The correction factors are meant to increase the engine load due to weather and hull fouling, and to decrease the engine load for some large vessels where maximum speed corresponds to a lower engine load.

(3)\[P_i = Load_i \times P_{max}\]

(4)\[Load_i = \left( \frac{draught_i}{draught_{design}} \right)^{\frac{2}{3}} \times \left( \frac{speed_i}{speed_{max}} \right)^3 \times CF\]

Where

• \(i\) is hour

• \(draught_{i/design}\) is the vessel’s draught at hour i / design draught

• \(speed{i/max}\) is the vessel’s speed at hour i / maximum speed

• \(CF\) is the correction factor

For the auxiliary engine and boiler, the power demanded is simplified as either a fraction of the main engine power or a fixed value according to the vessel’s type, size, and operational phase.

Per the GHG study, engines that operate at engine load less than 20% have lower combustion efficiency and therefore higher emissions. To account for this, the load correction factor (LCF) is applied as a multiplier when engine load is less than 20% with varying values across GHG and ranges of engine load.

Specific Fuel Consumption

Power demanded is converted to fuel consumption using a baseline specific fuel consumption (SFC) adjusted by the load correction factor (LCF). The baseline SFC is a fixed value that varies across engine type, fuel type, and year of built. The load correction factor (LCF) is a parabolic function that results in high values for both low and high inputs of engine load, and low values with engine load near 80%. LCF is only applied for oil and LNG engines for the main engine.

(5)\[SFC_{E,i} = P_{E,i} SFC_{base} LCF_{i}\]

Where

• \(i\) is hour

• \(P_i\) is the power demanded at hour \(i\)

• \(SFC_{base}\) is the baseline specific fuel consumption

• \(draught_{i/design}\) is the vessel’s draught at hour i / design draught

• \(LCF_i\) is the load correction factor function at hour i

Data Exploration

AIS data is extracted by Exclusive Economic Zones (EEZ) from 2019 to May 2024. The charts below show the number of unique vessels per month for each economic zone.

For each vessel journey, we calculate the total emissions of various GHG components. The below summarizes monthly CO2 emissions by type of vessel (Cargo, Tanker, Fishing, Passenger, or Other). Toggle the area of interest to explore emissions by country.

The following grid expresses the same data as a stacked bar chart to explore the share of emissions produced by each vessel type.

Similarly, the tree map below shows the annual composition of CO2 emissions across areas and vessel types.

We also calculate emissions for other GHG and pollutants, including Particulate Matter and Methane. Each line in this chart represents total monthly emissions for a specific pollutant.

Data Availability

The output dataset contains monthly GHG emissions disaggregated by vessel type, status of operation and country. The dataset is publicly available through the Development Data Catalog. You can download the data as an excel spreadsheet using this link.

Metadata

The dataset contains the following fields.

Field	Definition
Country	Indonesia
year	year
month	month
type	Type 1&2 - with Ship Register data, Type 3 - without Ship Register data
_vessel_group_ais	“Cargo, Tanker, Fishing, Passenger, Others Type 3 is based on vessel_type field in ais, Type 1&2 based on Ship Register”
_vessel_class_no	Type 1&2 only, follows IMO grouping
_vessel_class	Type 1&2 only, follows IMO grouping
_w_fishing	Flag to indicate if the hourly activity is a fishing activity according to GFW data
_op_phase	At Berth, Anchored, Maneouvring, Sea (increasing speed)
count_vessel	Count of unique vessels
count_vessel_day	Total number of days of activity for all vessels
_missing_hours	Total number of hours of activity interpolated due to missing AIS data
_total_hours	Total hours of activity
_ch4_energy	Main engine emission for CH4 (Methane)
_co_energy	Main engine emission for CO (Carbon Monoxide)
_n2o_energy	Main engine emission for N2O (Nitrous Oxide)
_nmvoc_energy	Main engine emission for NMVOC (Non-Methane Volatile Organic Compounds)
_pm10_energy	Main engine emission for PM10 (Particulate Matter)
_pm25_energy	Main engine emission for PM2.5 (Particulate Matter)
_nox_energy	Main engine emission for NOx (Nitrogen Oxide)
_bc_energy	Main engine emission for BC (Black Carbon)
_ch4_energy_pilot	Pilot fuel emission for CH4 (Methane)
_co_energy_pilot	Pilot fuel emission for CO (Carbon Monoxide)
_n2o_energy_pilot	Pilot fuel emission for N2O (Nitrous Oxide)
_nmvoc_energy_pilot	Pilot fuel emission for NMVOC (Non-Methane Volatile Organic Compounds)
_pm10_energy_pilot	Pilot fuel emission for PM10 (Particulate Matter)
_pm25_energy_pilot	Pilot fuel emission for PM2.5 (Particulate Matter)
_nox_energy_pilot	Pilot fuel emission for NOx (Nitrogen Oxide)
_bc_energy_pilot	Pilot fuel emission for BC (Black Carbon)
_ab_ch4_energy	Auxiliary Boiler emission for CH4 (Methane)
_ab_co_energy	Auxiliary Boiler emission for CO (Carbon Monoxide)
_ab_n2o_energy	Auxiliary Boiler emission for N2O (Nitrous Oxide)
_ab_nmvoc_energy	Auxiliary Boiler emission for NMVOC (Non-Methane Volatile Organic Compounds)
_ab_pm10_energy	Auxiliary Boiler emission for PM10 (Particulate Matter)
_ab_pm25_energy	Auxiliary Boiler emission for PM2.5 (Particulate Matter)
_ab_nox_energy	Auxiliary Boiler emission for NOx (Nitrogen Oxide)
_ab_bc_energy	Auxiliary Boiler emission for BC (Black Carbon)
_ae_ch4_energy	Auxiliary engine emission for CH4 (Methane)
_ae_co_energy	Auxiliary engine emission for CO (Carbon Monoxide)
_ae_n2o_energy	Auxiliary engine emission for N2O (Nitrous Oxide)
_ae_nmvoc_energy	Auxiliary engine emission for NMVOC (Non-Methane Volatile Organic Compounds)
_ae_pm10_energy	Auxiliary engine emission for PM10 (Particulate Matter)
_ae_pm25_energy	Auxiliary engine emission for PM2.5 (Particulate Matter)
_ae_nox_energy	Auxiliary engine emission for NOx (Nitrogen Oxide)
_ae_bc_energy	Auxiliary engine emission for BC (Black Carbon)
_co2_fuel	Main engine emission for CO2 (Carbon Dioxide)
_sox_fuel	Main engine emission for SOx (Sulphur Oxide)
_bc_fuel	Main engine emission for BC (Black Carbon)
_co2_fuel_pilot	Pilot fuel emission for CO2 (Carbon Dioxide)
_sox_fuel_pilot	Pilot fuel emission for SOx (Sulphur Oxide)
_bc_fuel_pilot	Pilot fuel emission for BC (Black Carbon)
_ab_co2_fuel	Auxiliary Boiler emission for CO2 (Carbon Dioxide)
_ab_sox_fuel	Auxiliary Boiler emission for SOx (Sulphur Oxide)
_ab_bc_fuel	Auxiliary Boiler emission for BC (Black Carbon)
_ae_co2_fuel	Auxiliary engine emission for CO2 (Carbon Dioxide)
_ae_sox_fuel	Auxiliary engine emission for SOx (Sulphur Oxide)
_ae_bc_fuel	Auxiliary engine emission for BC (Black Carbon)
_ch4_e	Total emission for CH4 (Methane)
_co_e	Total emission for CO (Carbon Monoxide)
_n2o_e	Total emission for N2O (Nitrous Oxide)
_nmvoc_e	Total emission for NMVOC (Non-Methane Volatile Organic Compounds)
_pm10_e	Total emission for PM10 (Particulate Matter)
_pm25_e	Total emission for PM2.5 (Particulate Matter)
_nox_e	Total emission for NOx (Nitrogen Oxide)
_bc_e	Total emission for BC (Black Carbon)
_co2_f	Total emission for CO2 (Carbon Dioxide)
_sox_f	Total emission for SOx (Sulphur Oxide)
_bc_f	Total emission for BC (Black Carbon)