Retailer is asking customers to recycle old flip-flops that can then be used to help build playgrounds. Concord’s Old Navy store is flipping out about Earth Day. Beginning today and running through May 21, shoppers at the store can bring in old flip-flops for recycling, turning those summer shoes into children’s playgrounds. By bringing in these hard-to-recycle products to their local stores, consumers help keep waste out of their community landfills, said Stacey Cusack, the spokesperson for TerraCycle, the New York-based “upcycling” and recycling company that is working wth the clothing chain to urge the recycling. Founded in 2001, TerraCycle is the world’s leader in the collection and reuse of non-recyclable post-consumer waste, Cusack says.