Although decay of organic materials under normal environmental conditions is sometimes slow, most organics ultimately break down to humus that helps to build topsoil.
Many factors affect the composting process, but moisture content often is the most crucial.
At moisture levels above 60 percent, small pore spaces that allow oxygen to move into the compost become filled with water. Lacking sufficient oxygen for rapid growth, aerobic microorganisms that produce relatively little odor are soon replaced by anaerobic organisms that produce highly odorous organic acids and hydrogen sulfide. For optimum performance, maintain moisture content between 40 and 60 percent. The compost should be moist but not soggy. If moisture can be squeezed from a handful of compost material, it probably needs to be mixed with drier material.