Estimating the Cost of Biofuel Use to Mitigate International Air Transport Emissions: A Case Study in Palau and Seychelles

International air transport is one of the fast-growing sources of CO2 emissions. However, it has always been omitted from the international emission mitigation pledges. The delayed mitigation process in this area may slow down the process of global CO2 emission control. In this article, we evaluated the potential to realize the emission mitigation targets in air transport through biofuel and estimated the corresponding cost. The emission from international air transport of Palau and Seychelles was taken as the example. Then, the emission caused by each airline to these two islands was calculated by the distance-based method, with information of the travelers' arrival data, fuel consumption of different aircraft types, routes, and aircraft seat data. Future scenarios with and without commitment to CO2 mitigation targets were predicted to evaluate the emission difference. Then, we estimated the amount of biofuel required to fill the emission gap, and the corresponding cost based on the future biofuel price prediction. The results show that distance is the determining factor of international air transport emission per capita. The component of origin can decrease the aggregated emission per capita to small island destinations by 0.5-2%. The accumulated emission gaps are 3.15 Mt and 9 Mt for Palau and Seychelles, which indicates that 7.64 and 19.34 Mb of biofuel are needed for emission mitigation, respectively. The corresponding costs are $27-163 million and $72-424 million per year.