Phosphorus recovery from organic waste for its agronomic valorization: technical and economic evaluation

Abstract

BACKGROUND: The present work investigates the use of municipal mixed waste compost (MMWC) residue for phosphorus (P) recycling from a technical, economic, and environmental perspective. The study aims to obtain liquid extracts rich in P from MMWC with a low heavy metals content, suitable for their subsequent precipitation in the struvite form. The effect of inorganic (sulfuric/nitric) and organic (oxalic/citric) acids at different molarities and temperatures was studied using technical analysis. The preliminary economic analysis allows the costs of the extraction section for the optimal extraction strategies to be estimated and compared.RESULTS: Based on the multilevel factorial design, the P extraction optimization shows that sulfuric acid 0.5 M and 30 °C provided the highest P extraction yield, 94.2%. However, oxalic acid 0.1 M and 30 °C is the best choice to maximize the P extraction yield, while also minimizing the heavy metals concentration, reaching a P recovery of 2.5 g P/kg. The extraction kinetics for all tested acids were satisfactorily modelled using a second-order model (r 2 > 0.99). The preliminary economic analysis, estimated for a P extraction pilot plant of 100 kg h −1 of MMWC, noted that sulfuric acid 0.5 M provided the lowest total investment cost (130 000 €) and a minimum sale price of theoretical struvite at 4.96 €/kg. CONCLUSION: MMWC is a promising raw material for P recycling as fertilizer due to an appreciable P concentration (7 g P/kg), which can be used together with other residues rich in P to obtain an economical and sustainable extraction process.

Phosphorus and potassium recovery from anaerobically digested olive mill wastewater using modified zeolite, fly ash and zeolitic fly ash: a comparative study

“…Therefore, this fraction contributed to 79.9%, 50.3% and 32.6% of the total q des of CaT‐Z, ZFA and FA, respectively, being the dominant fraction on the loaded CaT‐Z and ZFA, and the second dominant fraction on FA. These values are comparable to the NaHCO 3 ‐P amounts (0.96–2.82 mg P g −1 ) extracted from animal manures 77 and higher than those recovered by the acidic extraction of municipal waste compost 17 or the very low concentrations of Olsen‐P in Greek agricultural soils 81,82 . This fraction is readily exchangeable and adsorbed through electrostatic forces of attraction resulting in formation of outer‐sphere complexes (nonspecific adsorption) between functional groups of the adsorbent surface and the dominant HPO 4 2− anions at pH > 7.2 25,70 …”

“…6,8 However, the research interest in nutrient recovery from raw or digested OMW is still limited. [9][10][11] To recover P from wastes and wastewater, various biological and physicochemical processes have been suggested such as formation of aerobic granular sludge, 12 chemical or electrochemical precipitation of struvite 9,13 and calcium phosphate, 14,15 electrodialytic and acidic extraction, 16,17 membrane filtration, distillation and bioreactors, 18,19 and adsorption on hybrid anion exchange resins, 20 natural minerals, 21 biochar 22 and industrial byproducts. 23,24 Numerous studies of phosphate (PO 4 3− ) adsorption from aqueous solutions using abundant materials, such as coal fly ash (FA) and modified zeolites, have given promising results.…”

Phosphorus Recovery from Sewage Sludge as Struvite

“…Still, it should be highlighted that it has been defined only in the operation conditions range studied and taking into account only the phosphorus recovery. An additional economical study will be necessary to determine the parameters that, in addition to maximizing the P recovery, could minimize the costs of the process [43].…”

Circular Economy Model Through Phosphorus Recovery to Obtain Struvite from Sewage Sludge

“…Still, it is emphasized that it has been defined only in the range studied and taking into account only phosphorus recovery. An additional economical study will be necessary to determine the parameters that, in addition to maximizing the recovery, it is necessary to minimize the costs [40].…”