Composting is a natural process , it contains macro and micronutrient fibers often that are absent in the synthetic fertilizers. Composting also releases nutrients slowly over months or years unlike synthetic fertilizers. The compost buffers the soil neutralizing both acid and alkaline soils bringing ph levels to the optimum range for nutrient availability to plants. Compost helps bind clusters of soil particles called aggregates which provide good soil structure , such soil is full of tiny air channels and pores that hold air , moisture , and nutrients. Earth worms are also a great benefit of having in compost because they build tunnels through the dirt. The tunnels create percolation of water into the soil. You can use leafs , vegetables , peanut shells , newspaper shreddings , or bark in your compost.
The pictures are of phoenix school kids fixing the compost piles by going through them and sorting the dirt. The kids were putting the dirt into wheel barrows that had a mesh screen to sort pieces of compost ,getting rid of huge twigs, piles of dirt clumped together, or rocks.