There is no waste in functioning natural ecosystems. All organisms, dead or alive, are potential sources of food for other organisms. A caterpillar eats a leaf; a robin eats the caterpillar; a hawk eats the robin. When the plant, caterpillar, robin, and hawk die, they are in turn consumed by decomposers.
One hundred trout are needed to support one man for a year. The trout, in turn, must consume 90,000 frogs, that must consume 27 million grasshoppers that live off of 1,000 tons of grass.