According to companies that handle curbside recycling, the worst items found in single-stream recycling bins are plastic shopping bags. They are the absolute last things you should put in a recycling bin. When they show up in loads of recyclables, the flimsy plastic has to be sorted, removed and disposed of as trash. And worse? Those that aren't caught wind around recycling machines and clog the system. Instead, bring clean plastic bags to designated recycling bins at your local grocery store.