Digestate stability: Comparison between one-stage and two-stage anaerobic digestion process

The Bio2Energy project aims at improving the efficiency of public utility facilities using anaerobic digestion process. This purpose is carried out through the production of bio-fuels and bio-products such as digestate. The use of digestate as agricultural fertilizer and soil conditioner is one of the objectives of the project that position it within the Circular Economy concept. The aim of this work is to compare the performance of the traditional one-stage anaerobic digestion process with its implementation in a two-stage process in terms of outgoing digestate stability. The stability index is assessed using SOUR test. This respirometric technique allows to determine anaerobic digestion process efficiency and which configuration between one-stage and the two-stage process has better results referring to digestate biostabilization. The configuration with the dark fermentation used as preliminary treatment of anaerobic digestion process results to be the most efficient in terms of stability index. This configuration allows 79.42% of SOUR reduction for the out coming digestate in particular with a typical co-digestion substrate.