Oyster mushrooms (Pleurotus ostreatus) thrive on agricultural leftovers like coffee husks, banana leaves, rice straw, and other common farm byproducts — turning waste into high-yield food. Across dozens of tested substrates, mushrooms grew vigorously, produced strong biological efficiency, and left behind nutrient-rich spent substrate that improved soil structure and fertility. This circular model means farmers can convert low-value waste into edible mushrooms while returning enriched material to the fields, creating a closed-loop, low-cost, sustainable cultivation system.