Agronomic and energy value of digestate from anaerobic digestion of trout byproducts: Contribution to the autonomy of freshwater farms in Morocco

Abstract

Anaerobic digestion is a technology used to treat organic waste and recover biogas and digestate. In this study, three subjects were investigated: agronomic and microbiological characterization of the digestate obtained at the end of anaerobic digestion, co-digestion of rainbow trout byproducts (RTBP) and their digestate, and a combined pre-treatment (thermal pre-treatment of RTBP at 110 °C for 30 min followed by co-digestion with their digestate). Experiments were carried out in biodigesters operating at mesophilic temperature and with batch feeding mode. The results showed that the digestate is rich in the nutrients required for plant development, and also contains fungi (mycelial fungi, yeasts) that break down organic compounds and help maintain the soil's biological stability. The methane yield for co-digestion was 289.44 Nml/g.VS with a biodegradability of 64.34 %, while for combined pre-treatment, the methane yield was 267.95 Nml/g.VS with a biodegradability of 60.46 %. Five kinetic models were used in this research to estimate theoretical methane production (Modified Gompertz, First order, Transference function, Modified Richard, and Logistic function). The two models, Modified Richard and Logistic function, presented results identical and close to those of the study that dealt with co-digestion, whose methane yield was 294.45 Nml/g.VS; and for combined pretreatment, the Modified Gompertz model showed a methane yield equal to 262.97 Nml/g.VS and is the closest to the experimental one.