Parents looking to get rid of their children’s outgrown car seats can trade them in from Sept. 16 to Sept. 30 at Walmarts across the country for a $30 gift card.   In honor of National Baby Safety Month, customers can trade in up to two car seats each. All collected car seats will then be recycled through Trenton-based TerraCycle, and each component will be diverted from the landfill.   “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 for a gift card, perfect for using on your baby’s next car seat,” said Walmart Baby Vice President Melody Richards in a prepared statement. “Sustainability is of equal importance to Walmart, so we’re happy to work with TerraCycle who will recycle every component of the car seats.”   Through the event, TerraCycle Chief Executive Officer Tom Szaky said he expected to divert the plastic equivalent of approximately 35 million water bottles from landfills.