Combining Novel Membrane Technologies for Sustainable Nutrient Recovery from Digestate: Effect of Solid Content

Berta Riaño, Verónica Oliveira (), Celia Dias-Ferreira, Beatriz Molinuevo-Salces and Maria Cruz García-González
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Berta Riaño: Agricultural Technological Institute of Castilla y León (ITACyL), Ctra. Burgos, km. 119, 47071 Valladolid, Spain
Verónica Oliveira: Polytechnic University of Coimbra, Rua da Misericórdia, Lagar dos Cortiços—S. Martinho do Bispo, 3045-093 Coimbra, Portugal
Celia Dias-Ferreira: Research Center for Natural Resources, Environment and Society (CERNAS), Polytechnic University of Coimbra, Bencanta, 3045-601 Coimbra, Portugal
Beatriz Molinuevo-Salces: Department of Agroforestry Sciences, Escuela Técnica Superior de Ingenierías Agrarias de Palencia, University of Valladolid, Avenida de Madrid 44, 34004 Palencia, Spain
Maria Cruz García-González: Department of Agroforestry Sciences, Escuela Técnica Superior de Ingenierías Agrarias de Palencia, University of Valladolid, Avenida de Madrid 44, 34004 Palencia, Spain

Sustainability, 2025, vol. 17, issue 7, 1-20

Abstract: Nutrient recovery from anaerobic digestate has gained increasing importance in recent years due to its potential to reduce resource dependency and to close nutrient cycles. The aim of this work is to evaluate the influence of a previous solid–liquid separation phase on nutrient recovery efficiency using two innovative membrane technologies, namely, gas-permeable membranes (GPM) and electrodialytic (ED) processes, applied individually or in combination. The obtained results were compared with those obtained through the centrifugation of the raw digestate and direct chemical precipitation followed by centrifugation in terms of the efficiency in the recovery of N (nitrogen) and P (phosphorous). A total of nine scenarios of digestate processing were compared. GPM technology allowed for the recovery of 65% of the N content in the raw digestate (41.5 g total solids (TS) kg −1 ) and 67% of N in the liquid fraction (28.0 g TS kg −1 ), without any significant difference between the two scenarios. However, the results revealed significant differences in the P recovery with ED from the raw digestate (15%) and the liquid fraction (34%), suggesting that phosphorous extraction can be improved by the application of a prior solid–liquid phase. The recovery of N with the GPM technology also enhanced the further recovery of total P with the ED processes. Furthermore, the combination of these technologies allowed for the recovery of N- and P-rich solutions, which were used to precipitate secondary struvite with an efficiency of up to 85%. This research provides a practical framework for sustainable nutrient management, advancing solutions for resource efficiency and environmental stewardship.

Keywords: nitrogen; phosphorous; chemical precipitation; gas-permeable membrane; electrodialytic process; sustainable use of resources (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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