What happens to landfills after they are no longer active?

They can be covered in topsoil, and left to digest. Things like cans of mountain dew and plastic wrappers will probably be an issue for a century, but otherwise sustainable with care. Abandoned Landfill Project Completed in Popular Nature Sanctuary. Please don't advertise though :-). read more

Of nine landfills in Massachusetts, three will have to close before the end of the decade. No new landfill has been built there for about 20 years. No new waste-to-energy plants have come online, either. In fact, the state had a moratorium on building new incinerators between 1990 and 2010. read more

I know of an ex-landfill site in Launceston, Tasmania, Australia where the site was regenerated to provide ‘open-space’ for the public. It now provides ‘neighbourhood’ facilities (walking, bbq and playground equipment) for families. read more

A municipal solid waste landfill (MSWLF) is a discrete area of land or excavation that receives household waste. A MSWLF may also receive other types of nonhazardous wastes, such as commercial solid waste, nonhazardous sludge, conditionally exempt small quantity generator waste, and industrial nonhazardous solid waste. read more