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 (r2 > 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. © 2021 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).