Compost is an essential element in organic gardening. Compost is made of decomposed organic matter that can be used to improve the health of garden soil. The compost adds humus, organic matter that cannot be broken down any further, to the soil. The humus aids in nutrient and moisture retention in the soil and also changes the density of the soil. Composting is not only beneficial for its soil-building properties; it also greatly decreases the amount of garbage that can end up in a landfill. The compost ingredients are naturally decomposed and reused instead of being thrown away. Compost can also help reduce the amount of toxins in soil due to pesticides or fuels. The compost can regenerate this soil and prevent the spread of the toxins to other plants and into water sources.