If you’re looking for somewhere to ditch an old car seat, Walmart has a deal for you.   The retail giant announced that from Monday to Sept. 30 it will offer customers a $30 gift card if they trade in an old seat. The promotion is good at nearly 4,000 U.S. stores.   If you’re interested in cashing in, contact Walmart Customer Service. There is a limit of two gift cards per household and booster-seat recycling is not included in this event.   “Safety — especially car seat safety — is a top priority for Walmart’s Baby department, so we wanted to use our size and scale to create an event that offered unprecedented access to trade in an outgrown car seat,” Walmart Baby Vice President Melody Richards said in a statement.   She added that sustainability is of “equal importance. So we’re happy to work with TerraCycle who will recycle every component of the car seats.”   The promotion comes as part of National Baby Safety Month and is held in conjunction with TerraCycle, a New Jersey-based recycling business that works with manufacturers to reprocess difficult products that would normally be thrown away.