t is the biological breakdown of organic materials by living anaerobic organisms (e.g. bacteria). As the word anaerobic implies, these organisms thrive in environments in the complete absence of oxygen. This differs dramatically from most of the other discussions we have been having on this site. Usually, we discuss the need for lots of oxygen within a compost pile; however, it must be noted that you can still obtain a breakdown of compost ingredients even in oxygen poor piles.