Let’s talk about gardening technology. Not some fancy gadget for monitoring water or sunlight, but technology that feeds the dirt itself. Washington, D.C.’s wastewater-treatment plant is one of the largest high-tech plants in the world. It uses a process akin to pressure cooking to turn what’s flushed down the toilet into fertilizer fit for planters at home. Marketplace’s Kimberly Adams takes a tour to learn more about thermal hydrolysis tech.