The county government has sent nearly 50,000 stickers to trash-carting companies and local municipalities.
Other places - including the city of Durham, N.C. - have experimented with similar stickers.
Westchester County Executive Andrew Spano announced a recycling crackdown in November. The initiative includes inspecting more loads of garbage for misplaced recyclables and fining companies and municipalities that fail to separate them. Fines start at $250.