Well someone in the Seoul region is going to have to be host to a huge landfill since Incheon no longer wants to supply the land:

A waste disposal crisis is looming large in the Seoul metropolitan area for 2025 as Seoul, Incheon and Gyeonggi Province struggle to find alternative landfill sites that can replace the current one, according to environmental engineering experts.
Korea Times
In 2015, Seoul and Incheon cities, Gyeonggi Province and the Ministry of Environment set out to find a site to replace the current Sudokwon Landfill Site (SLS) which many claim is the world’s largest.
Opened in 1992, it receives an average of 12,000 tons of garbage daily, mostly home- and construction-related waste from Seoul, Incheon and Gyeonggi Province where half the country’s population lives. Years of meetings have been fruitless and a look into these reveals the complexity of waste management issues in Korea and conflicts of interest.
You can read more at the link, but authorities are considering holding a contest to see who wants the landfill in their city.