Granulated Poultry Litter Ash Acidulation and Physical Characteristics

Abstract

HighlightsPhosphoric acid (PA) increased water-soluble phosphorus (WSP) from 0.31 to 47.4 g P kg-1 in poultry litter ash (PLA).Ideal granule size was identified at 29% acidulation (14.5 g acid to 50 g PLA) with granules averaging 3.14 mm.Bulk fertilizer production needed 32% PA addition, and adequate mixing equipment is important for PA efficiency.Granule size and strength were adequate as compared to industry standards and commercial fertilizers.Abstract. Manure-to-energy systems effectively recycle poultry litter (PL) into poultry litter ash (PLA) that densifies and concentrates the phosphorus (P) content by a factor of 4 to 10. However, high conversion temperatures reduce nutrient solubility and produce small particulate materials. To redistribute manure nutrients beyond the original production location by improving the physical and chemical characteristics of PLA, the objectives of this research were to: (1) determine the phosphoric acid (H3PO4) acidifying effect on water-soluble P (WSP), measurable total P (TP), granulation point, and granule size and (2) conduct large-scale granulated poultry litter ash bulk (GPLA-B) granulation to determine the larger-scale formulations and granule physical characteristics produced. We measured bulk density, force and friction resistance, and granule size as compared to industry-standard triple superphosphate (TSP). Acidulation experiments were arranged in a completely randomized design with four replications per H3PO4 acidulation percentage. Increasing acidulation percentages from 0% to 50% H3PO4 (laboratory-grade white phosphoric acid) increased measurable TP from 50.63 to 116.90 g kg-1 and WSP from 0.31 to 47.4 g P kg-1 (LSD0.05 10.13 and 2.65 g P kg-1, respectively). Acidulation dose response relationships created simple linear regression equations to predict changes in measurable TP and WSP, pH, and exothermic reaction temperature, which all increased with acidulation. The loose (1.01 g cm-3) and packed (1.03 g cm3) bulk densities of GPLA-B were significantly less than those of TSP (1.14 and 1.30 g cm3, respectively) (LSD0.05 = 0.03 and 0.02 g cm-3). Compared to TSP particles (2.86 mm), GPLA particles (3.73 mm) were significantly larger (LSD0.05 = 0.61 mm); however, the force resistance of GPLA (4.53 kgf) was significantly less than that of TSP (5.95 kgf) (LSD0.05 = 0.61 kgf). Results showed that the physical characteristics of GPLA met industry standards and validated the adaptability of GPLA as an alternative P source. Furthermore, GPLA has higher elemental analysis, greater solubility, and improved form, which addresses the undesirable characteristics of ungranulated PLA and supports the use of GPLA for fertilizer and nutrient distribution. Keywords: Acidulation, Fertilizer, Granulation, Phosphorus, Poultry litter ash.