There’s a smell emanating from my kitchen.

The days are marching toward Tokyo’s unrelenting, mold-inducing summer, but I’m not concerned: This odor is earthy, rich and fragrant.

I’m making compost in a cardboard box, a method that’s become popular in Japan over the past decade. The cardboard box composting system’s draw is that it is both cheap and simple, bad-odor-free and well-suited to small Japanese spaces. I don’t need to buy any special equipment apart from coconut peat and kuntan (rice husk ash), both of which are readily available from gardening centers. Nor do I need a special place to set my box up, though sunlight and ventilation are important for success.