<P> In an aerobic system, such as composting, the microorganisms access free, gaseous oxygen directly from the surrounding atmosphere . The end products of an aerobic process are primarily carbon dioxide and water which are the stable, oxidised forms of carbon and hydrogen . If the biodegradable starting material contains nitrogen, phosphorus and sulfur, then the end products may also include their oxidised forms - nitrate, phosphate and sulfate . In an aerobic system the majority of the energy in the starting material is released as heat by their oxidisation into carbon dioxide and water . </P> <P> Composting systems typically include organisms such as fungi that are able to break down lignin and celluloses to a greater extent than anaerobic bacteria . Due to this fact it is possible, following anaerobic digestion, to compost the anaerobic digestate allowing further volume reduction and stabilisation . </P>

What is the similarity between digestion and decomposition