Anaerobic digestion is a series of processes by which microorganisms decompose biodegradable materials in the absence of oxygen. The process is used for industrial or domestic purposes in waste management and/or fuel production.

Anaerobic digestion occurs naturally in some soils and in sediments of lakes and ocean basins, where it is commonly referred to as “anaerobic activity”. Anaerobic digestion is a source of methane as discovered by Alessandro Volta in 1776.

As part of an integrated waste management system, anaerobic digestion reduces landfill gas emissions to the atmosphere. Anaerobic digestion systems – reactors can also be fed with energy crops such as corn, rapeseed, etc.

Anaerobic digestion is widely used as a source of renewable energy. The process produces biofuel, consisting of methane & carbon dioxide as well as traces of other ‘impurity’ gases. Biogas can be used directly as a fuel in gas engines for combined heat and power. The resulting nutrient-rich product of digestion can also be used as a fertiliser.
Biodegradable wastes that can be used in ANEROBIC FUMIGATION SYSTEMS (alone or in combination) are:

1. commercial food waste (catering waste),
2. forestry residues (tree bark, woody debris),
3. agricultural waste (farmyard manure, crop residues, etc.)
   According to the Greek Statistical Service (ESS), in 2014 the total estimated annual amount of animal waste (manure) amounted to 11.529 million tonnes. Based on European and Greek legislation, to prevent nitrate pollution of water, it is prohibited to dispose manure directly into the soil without prior treatment in order to reduce the pollutant load. The use of which is a successful method of organic waste management.
4. waste from the food and drink industry (breweries, wineries, oil mills, fruit and vegetables, meat and meat products, cheese milk, etc.) and of course
5. the sewage sludge.