Characterisation of ashes from waste biomass power plants and phosphorus recovery

• Published in: The Science of the total environment Vol. 690; pp. 573 - 583
• Main Authors: Leng, Lijian, Bogush, Anna A., Roy, Amitava, Stegemann, Julia A.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 10.11.2019
• Subjects: Acid neutralization capacity; Animal manure; Fertiliser; Incineration; Phosphorus recovery; Acid neutralization capacity; Animal manure; Incineration; Phosphorus recovery; Fertiliser
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.06.312

Biowastes, such as meat and bone meal (MBM), and poultry litter (PL), are used as energy sources for industrial combustion in the UK. However, the biomass ashes remaining after combustion, which contain nutrients such as phosphorus, are landfilled rather than utilised. To promote their utilisation, biomass ashes from industries were characterised in terms of their elemental and mineral compositions, phosphorus extractability, and pH-dependent leachability. These ashes were highly alkaline (pH as high as 13), and rich in calcium and phosphorus. The P bio-availabilities in the ash evaluated by Olsen's extraction were low. Hydroxyapatite and potassium sodium calcium phosphate were identified by X-ray powder diffraction (XRD) as the major phases in the MBM and PL ashes, respectively. The leaching of P, Ca, and many other elements was pH dependent, with considerable increase in leaching below about pH 6. P recovery by acid dissolution (e.g., with H2SO4) seems feasible and promising; the optimized acid consumption for ~90% P recovery could be as low as 3.2–5.3 mol H+/mol P. [Display omitted] •Meat and bone meal (MBM) and poultry litter (PL) biomass ashes were characterised.•P is mainly Ca5(PO4)3(OH) in MBM ashes and KNaCa2(PO4)2 in PL ashes.•P recovery by acid dissolution seems feasible and promising.•Optimized acid consumption for ~90% P recovery is as low as 3.2–5.3 mol H+/mol P.