Valorization of anaerobic digestion liquid residue through the production of organic fertilizer by fluidized bed granulation

Abstract

In this work the feasibility of developing a solid fertilizer by fluidized bed granulation, using digestate (liquid residue from anaerobic digestion) as binder and different minerals as seeds is analysed. Full characterization of the selected mineral particles and the liquid digestate was performed. Particularly, phosphorous and potassium content was assayed before and after granulation. Friability and breakage strength of product granules were tested as well. Also, the process operating conditions (bed temperature, fluidization air temperature and flowrate, digestate temperature and flowrate, etc.) that enable stable operation and the production of completely coated granules were successfully established for lab- and pilot-scale granulation units.