Binding Agents Affect on Physical and Chemical Attributes of Nitrogen Fortified Poultry Litter and Biosolids Granules.

Northwest Arkansas (NWA) is a region of high density confined animal feeding operations (CAFO) that produces annual surpluses of poultry litter (PL) and municipal biosolids (BS) that can be used in organic fertilizer formulations. The objective of this study was to evaluate the effect of various binding agents and a nitrification inhibitor [dicyandiamide (DCD)] on granule physical strength and nutrient water solubility. We produced 4 different granule formulations using agglomeration techniques with a pin mixer in a 2 × 2 × 3 factorial arrangement. Treatments included granules with and without BS, with and without DCD, and bound with lignosulfonate, urea formaldehyde, or water. These 12 granular products were tested for bulk density, physical strength and water soluble N and P. Overall, granulated products were bulkier (0.48 to 0.64 g cm^-3) than commercial urea fertilizer and BS (0.81 and 0.76 g cm^-3, respectively), but had a higher bulk density than fresh PL (0.40 g cm^-3). Compared to urea and triple super phosphate (TSP) fertilizers, granules were more resistant to crumbling during force crush tests but degraded faster during attrition tests. Generally, the heat dependent granulation process increased granule DRP concentrations by up to 278% compared to unprocessed ingredients. Based on ingredient and production costs, granules can be produced for $0.82 to $1.24 per kilogram of N, similar to commercially available urea ($0.99 kg^-1 N). Organic, granular fertilizers also contain other macro and micronutrients that adds additional value to the formulations not accounted for in this study. Using the granulation process, significant amounts of PL and BS could economically be transported out of sensitive nutrient surplus watersheds in NWA to areas suffering from nutrient deficiencies.