The unused car seat that's sitting in your garage is worth $30 in Walmart merchandise. Nearly 4,000 U.S. Walmart stores are now handing out $30 gift cards in exchange for old car seats. The trade is being sponsored by TerraCycle, a waste management company that specializes in "difficult to recycle" items -- a category that includes car seats. According to TerraCycle's Tom Skazy, the drive is expected to eliminate the "plastic equivalent of approximately 35 million water bottles from landfills." The program, which coincides with National Baby Safety Month, runs through September 30th. Booster seats are not eligible for trade in.