Engineered Pelletized Organo-Mineral Fertilizers (OMF) from Poultry Manure, Diammonium Phosphate and Potassium Chloride

In this work, we engineered a pilot scale process for the production of granulated organic- and organo-mineral fertilizers (OGF and OMF) from poultry manure. We investigated the effects of moisture content in the manure, energy consumption during the three main stages of the process and the possibility to obtain nutrient balanced fertilizers using conventional straw drying and granulation equipment, common on the farms. Poultry manure was dried and shredded to no less than 90% of dry mass at 95 °C. Granulation was performed via extrusion with and without mineral additives, such as diammonium phosphate (DAP) and potassium chloride (KCl). This process was used to achieve 4-3-3 OGF, as well as tunable NPK content (4-4-2, 4-3-6 and 4-4-9) OMF. Energy consumption as the manure dried was about 100 kWh/t of product. This limiting step of the process suggests that the maximum achievable drying of sub 10% water currently commonly used is not necessarily economically optimal. DAP was used to increase water-soluble phosphate concentration and was limited to 6% of the total amount by the emission of ammonia during the granulation process. Additionally, the presence of hygroscopic KCl in combination with DAP resulted in significant moisture absorption and loss of the granulized pellet structural integrity after 72 h at 30 °C and 80% RH. Significant increases in yields of rapeseed and potato crops were observed with the 2 t/ha application of OGF or DAP/KCl enhanced OMF. The engineered process will provide for sustainable production of nutrient balanced organo-mineral fertilizers on the manure production sites using conventional equipment already used for straw processing.