Effect of wheat straw and peat additives on mechanical strength of poultry manure granules

Granulation of poultry manure (PM) converts malodorous and logistically challenging waste into a high‑value organic fertiliser suitable for precision agriculture. The mechanical durability of granules is essential to ensure reliable handling, transport, and field application. This study assessed the chemical characteristics of raw materials and granules, as well as the mechanical strength of PM granules produced without additives and with wheat straw (WS) or natural peat (NP). Granules were formed from fresh PM (two samples), PM with 2.5% and 7.5% WS, and PM with 7.5% and 15.0% NP. Pre‑drying was carried out to 25% moisture either at 24 °C or using a combined regime of 1 h at 70 °C followed by drying at 24 °C. Granulation was performed using a KL200B/C pellet press with 6 mm die openings, and final drying to 10-12% moisture was completed at 24 °C. Laboratory analyses determined total solids, volatile solids, and N, P, and K concentrations. The highest compressive strength (13.6 MPa) was obtained for granules containing 15% NP, while the lowest strength (7.9 MPa) occurred in granules with 5% WS. Pure PM granules pre‑dried at 70 °C for 1 h exhibited higher strength (12.8 MPa) than those dried solely at 24 °C (11.9 MPa). Overall, all granule types demonstrated sufficient mechanical integrity for handling and application without risk of structural failure.