This book chapter begins with an overview of the chemical, physical, and biological changes that occur during thermophilic composting, thereby providing an example of how several sciences can be integrated in the study of composting. The overview is followed by more detailed, separate sections on compost chemistry, physics, and biology.

Much of the information in the chemistry and physics sections focuses on thermophilic composting.

The biology section includes a discussion of the microbes that are present in all types of composting, and of the diversity of invertebrates that live in outdoor and some worm composting systems.