There is an unnecessary debate about aerobic composting vs. Anaerobic digestion, as if they are mutually exclusive. They aren't. In fact, they are complementary. Generally the most efficient way to get value out of so-called waste materials when they are organic, is to let the anaerobic consortia work on them through digestion in an air free environment, capturing the energy rich CH4 bonds as the gaseous byproduct known as biogas. Then the liquid and solid materials left over from anaerobia pass to an aerobic composting operation where thermophilic organisms release even more energy that can be captured as heat while producing a safely cured compost.