As the calculation of GHG emissions depends on the emission
factors used in the study, a Monte Carlo simulation was performed
to evaluate how sensitive of the calculated GHG emissions due to
the uncertainty of emission factors. The range of emission values
for air freight was set to 912e963.45 g CO2-eq/tonne-km as suggested
by Cristea et al. (2013). The ranges of emission values for sea
and land freight were set based on the works of Cristea et al. (2013)
and other international/regional studies (Cadarso et al., 2010;
Psaraftis and Kontovas, 2009; Tarancon and del Río, 2007).
Scenario analysis was performed to determine how much GHG
emissions can be reduced by changing some percentage of a
particular mode of transport (for example air transport that produces
the largest amount of GHG per tonne-km of cargo) to another
mode such as sea and land transport.