MINDANAO, Philippines — Maggots are considered gross since they thrive best in stinky, decaying organic matter such as animal waste and plants. The mere sight of them in a household often prompts a frantic search for a can of insecticide. But in Davao City, the hometown of Philippine President Rodrigo Duterte, the black soldier fly or BSF (Hermetia illucens), an insect that many confuse with a wasp, is making a buzz as an innovative solution to address the problem of kitchen waste — benefiting both the environment and agriculture. Located 960 kilometers (600 miles) south of the capital Manila,...