Composted food scraps provide the trace minerals and elements that your plants need to be healthy, as long as you are eating a varied diet. Compost also holds a balance of organically producted N, P, and K. These are the key nutrients for fertility.
Compost provides a rich habitat for worms and other decomposers that create channels for air and water to follow.
Compost binds soil particles together, which helps to reduce erosion. It can also bind pollution and keep it from waterways and plants in your garden.
Compost increases the water-holding capacity of soil. The organic matter (carbon) in the compost holds four times its weight in water and releases it slowly. When your soil has good levels of carbon in it, you need to water less.
Organisms found in compost help keep pathogens and pests in check.