Properties of Poultry-Manure-Derived Biochar for Peat Substitution in Growing Media

Peat is considered a contentious input in horticulture. Therefore, there is a search for suitable alternatives with similar properties that can be used for partial or complete peat substitution in growing media. Poultry-manure-derived biochar (PMB) is considered such an alternative. This study aimed at determining the properties of PMBs obtained through pyrolysis at selected temperatures and assessing their potentials to substitute peat in growing media based on the selected properties. The scope included the laboratory-scale pyrolysis of poultry manure at the temperatures of 425-725 °C; the determination of selected physico-chemical and physical properties of the obtained biochars, including the contaminants; and the assessment of the potentials of produced biochars to be used as peat substitutes. PMBs contained less than 36% of total organic carbon (TOC). The contents of P and K were about 2.03-3.91% and 2.74-5.13%, respectively. PMBs did not retain N. They can be safely used as the concentrations of heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinatd biphenyls (PCBs), dioxins, and furans are within the permissible values (except for Cr). Due to high pH (9.24-12.35), they can have a liming effect. High water holding capacity (WHC) in the range of 158-232% w/w could allow for the maintenance of moisture in the growing media. PMBs obtained at 525 °C, 625 °C, and 725 °C showed required stability (H/C_org < 0.7).