Phosphorous and Silica Recovery from Rice Husk Poultry Litter Ash: A Sustainability Analysis Using a Zero-Waste Approach

Phosphate rocks are a critical resource for the European Union, and alternative sources to assure the future production of a new generation of fertilizers are to be assessed. In this study, a statistical approach, combined with a sustainability evaluation for the recovery of materials from waste containing phosphorus (P), is presented. This work proposes a strategy to recover P and silica (SiO2) from rice husk poultry litter ash (RHPLA). The design of experiment (DoE) method was applied to maximize the P extraction using hydrochloric acid (HCl), with the aim to minimize the contamination that can occur by leachable heavy metals present in RHPLA, such as zinc (Zn). Two independent variables, the molar concentration of the acid, and the liquid-to-solid ratio (L/S) between the acid and RHPLA, were used in the experimental design to optimize the operating parameters. The statistical analysis showed that a HCl concentration of 0.34 mol/L and an L/S ratio of 50 are the best conditions to recover P with low Zn contamination. Concerning the SiO2, its content in RHPLA is too low to consider the proposed recovery process as advantageous. However, based on our analysis, this process should be sustainable to recover SiO2 when its content in the starting materials is more than 80%.

Simultaneous amorphous silica and phosphorus recovery from rice husk poultry litter ash

Rice husk poultry litter ash (RHPLA) is proposed as a valuable secondary source to recover phopshorus and amorphous silica in three steps.

Granulated Poultry Litter Ash Acidulation and Physical Characteristics

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.

Fertilizer Efficacy of Poultry Litter Ash Blended with Lime or Gypsum as Fillers

Ash from power plants that incinerate poultry litter has fertilizer value, but research is lacking on optimal land application methodologies. Experiments were conducted to evaluate calcitic lime and flue gas desulfurization gypsum (FGDG) as potential fillers for poultry litter ash land applications. The ash had phosphorus (P) and potassium (K) contents of 68 and 59 g kg−1, respectively. Soil extractable P and K were measured in an incubation pot study, comparing calcitic lime to FGDG at filler/ash ratios of 1:3, 1:2, 1:1, 2:1, and 3:1. After one month, soils were sampled and annual ryegrass (Lolium multiflorum Lam.) seeds were planted to investigate how plant growth and uptake of P and K were influenced by the fillers. Application of ash alone or with fillers increased soil extractable P and K levels above unamended controls by 100% and 70%, respectively. Filler materials did not affect biomass or P and K concentration of the ryegrass. A field study with a commercial spinner disc fertilizer applicator was conducted to compare application uniformity of ash alone and filler/ash blends. Overall, test data suggested that uniform distribution of ash alone or with fillers is feasible in field applications using a commercial fertilizer spreader.