Feasibility of Struvite Crystals Obtained from Swine Wastewater and Urban Sewage Sludge Liquid Fraction as Fertilising Product

Rubén Rodríguez-Alegre, Sergi Durán-Videra, Manuel Cepero-Sánchez, Laura Pérez Megías, Carlos Andecochea Saiz and Xialei You ()
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Rubén Rodríguez-Alegre: Leitat Technological Center, Circular Economy & Decarbonization Department, Carrer de La Innovació 2, 08225 Terrassa, Spain
Sergi Durán-Videra: Leitat Technological Center, Circular Economy & Decarbonization Department, Carrer de La Innovació 2, 08225 Terrassa, Spain
Manuel Cepero-Sánchez: Leitat Technological Center, Circular Economy & Decarbonization Department, Carrer de La Innovació 2, 08225 Terrassa, Spain
Laura Pérez Megías: Leitat Technological Center, Circular Economy & Decarbonization Department, Carrer de La Innovació 2, 08225 Terrassa, Spain
Carlos Andecochea Saiz: Leitat Technological Center, Circular Economy & Decarbonization Department, Carrer de La Innovació 2, 08225 Terrassa, Spain
Xialei You: Leitat Technological Center, Circular Economy & Decarbonization Department, Carrer de La Innovació 2, 08225 Terrassa, Spain

Sustainability, 2025, vol. 17, issue 13, 1-15

Abstract: Increasing global food demand has led to an intensive use of synthetic fertilisers. In this regard, the use of non-conventional streams such as swine wastewater (SW) and urban sewage sludge liquid fraction (USS) for the production of bio-based fertilisers can increase the sustainability of both the fertiliser industry and agriculture while reducing the reliance on imported nutrients. In this work, USS and SW were assessed for the production of struvite at different PO 4 3− :Mg 2+ ratios. Significant differences were found in terms of struvite crystals’ shape and size among both feedstocks due to the different saturation indexes, and it was concluded that PO 4 3− :Mg 2+ ratios of 1:2 for SW and 1:1 for USS were the most suitable for obtaining big crystals suitable to be used for direct fertilisation. In addition, it was observed that the crystallisation process is highly dependent on the presence of interfering ions (mainly Ca) that can result in the formation of hydroxyapatite instead of struvite. Finally, recovering struvite from SW and USS could potentially reduce the European import of P by up to 6.5%.

Keywords: struvite; crystallisation; swine wastewater; urban sewage sludge; circular fertiliser; circular economy (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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