A techno-economical case study of a thermophylic anaerobic digestion plant in Attica Region, Greece

Purpose: To present a techno-economical study of a possible thermophylic anaerobic biological degradation unit installation in Attica, which will manage 35600ton/y of fresh substrate of the source sorted organic fraction of solid municipal waste (SS-OFSMW). Methods: The anaerobic digestion unit consists of a pre-processing step (screening with hands-cutting) and the main dry anaerobic biological treatment. Two designs are taken into consideration. In the first case (Case 1) the biogas unit consist of one bioreactor while in the second case (Case 2) the main anaerobic part relies on two bioreactors. Both cases operate at high organic loading rate (OLR). Results: The thermophylic process can produce approximately 200m of biogas per ton of fresh substrate. These results are consistent with large-scale studies in the European Union where it is produced 100200mbiogas/ton. The thermophylic anaerobic biological treatment unit will produce almost 14787 MWh/y. The investment cost of the aforementioned processing unit will be around 15 million euro for Case 1 and 10% higher for Case 2. The average annual operational cost of such a unit is amounted to 700,000 euro. The pay back of the investment will be around 5 years for Case 1 and 6 years for Case 2. (Eurozone recession rates and the economical crisis in Greece the last four years are taken into consideration). Conclusions: By treating the 9.6% of annual organic waste production in Athens the 1.8-2.3% of Athens municipality electric energy demand can be covered.