Thousands of Derby homes will not have household recycling services even after an upcoming expansion of the system.
About half the 14,000 city centre households are to get recycling bins but the council is still considering how to include flats and apartments.
This type of residence does not have room for the traditional containers but their inclusion is important in reaching targets, a spokesman said.
He added they had ideas but wanted to be sure they were practical.
One idea was for lockable communal recycling bins which residents could take their own bags to.
City Waste Strategy Officer Rachel Bailey said: "We have made sure we got the easier schemes sorted out first before moving on to this problem.
"It requires solutions tailored to the particular areas and these have to be workable for all concerned as well as cost effective."