The term 'anaerobic digestion' when describing a process for managing waste refers to the bacterial breaking down of organic materials in the waste in the absence of oxygen. Wastes within a landfill site degrade in an anaerobic process, since the layers of waste are compacted and covered, excluding air. A compost heap provides a similar bacterial break-down, but in an oxygen-rich or aerobic atmosphere.
This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities. Agenda 21 recommends developing and encouraging processes for recycling organic and inorganic waste into the soil structure without harming the environment, plant growth or human health.