I'm reading an interesting book on Composting. That is taking organic waste and turning it into top soil. There's a whole science in this and nature does it very well. As soon as a plant, animal dies microbes start the process of making compost, old leaves, wood chips, and cow, horse manure. Nitrogen rich ingrediants replinish the soil, they come from animal and some plants.
The ecosystem is a closed end system meaning every part works perfectly.
Allmost all our trash can be composted except plastics and metals.