The Seoul Metropolitan Government announced Wednesday plans to have all 450 shuttle buses running between Incheon Airport and Seoul powered by clean energy by 2030.

Currently, all 450 airport buses are diesel-powered. Airport shuttle buses run about 550 kilometers a day on average -- shuttling from the airport to a final destination twice a day -- double that of city buses, meaning the amount of carbon they emit is 30 times more than that of sedans, according to Seoul city.

In Seoul city's plan, two-thirds of the current airport shuttle buses will be replaced with hydrogen-powered ones by 2026, and all of the buses will be replaced by 2030.

This scheme is in line with the green transition underway for city buses. By 2026, 1,300 buses, including airport shuttles and city buses, will be hydrogen-powered.

All of Seoul's 7,400 city buses transitioned to compressed natural gas by 2011. Among them, some 830 buses were replaced with electric buses, and 27 city buses now run on hydrogen.

In addition, hydrogen stations will be created in five public bus garages in Seoul, including one established in Gangseo-gu, Seoul last year. Seoul currently houses 13 hydrogen stations across the city.

Seoul city on Wednesday signed nonbinding agreements on the matter with the Ministry of Environment, liquefied hydrogen provider SK E&S, automotive manufacturer Hyundai Motor and mobility services firm Tmap Mobility.

These nonbinding agreements are in line with Seoul municipal government's green push, as nearly 20 percent of greenhouse gases are emitted in the field of transportation. Seoul has encouraged public transit operators and residents to adopt cars run on renewable energy.

Seoul in 2020 declared its goal of achieving carbon neutrality by 2050.