High-agronomic value of selected poultry manure valorized through aerobic fermentation: The AFRODITE® process

Chicken manure is a raw material with potential value as fertilizer. The present work documented an 8-month continuous spontaneous fermentation process, referred to as AFRODITE® (Aerobic Fermentation and Revaluation of Organic matrix to Develop and Improve The Essence of soil), where the main physical, chemical and microbiological parameters have been investigated for two years within the company FOMET S.p.A. The pelletized final product reached in both years stable value of pH (6.5–7.5), moisture (17.0–13.8%), total nitrogen (3.0–3.8%) and C/N ratio (10.46–10.66); total eubacteria population decreased (from 10 to 11 to about 7 Log CFU/g), with the selection of a thermophilic/hyperthermophilic microbiota due to the high temperatures during the process. The commercial product is microbiologically safe and rich of bacteria that were isolated and identified. The dominant species belong to the Bacillus genus, which includes several Plant Growth Promoting Rhizobacteria whose beneficial activities towards soil and plant are widely known. A greenhouse experiment in lettuce and eggplants showed the positive effect of two concentrations of the pelletized commercial product (2.5 and 5% w/w) in combination with a mixture of topsoil/river sand. In particular, 27% of fresh weight increase was observed in lettuce with both product amounts whereas the average production of eggplants was three times higher using 5% pelletized product compared to the untreated control. This work has highlighted that chicken manure fermentation followed by pelletization allows the obtainment of a stable product, rich in beneficial bacteria and nutritional elements, possessing growth-promoting effects on horticultural plants. The process represents a virtuous example of circular economy.