Advancing livestock waste valorization high-value irganomineral struvite fertilizer : a pilot-scale study
Date Issued
June 3, 2022
Abstract
The Mediterranean region faces significant challenges concerning food security and safety. A
major cause of this problem is the disposal of inadequately treated livestock waste in soil and
water resources with adverse environmental implications1,2. Currently, the most common
manure management practice is solid-liquid separation, while a small percentage of these
waste is anaerobically digested (6.4% in EU 273
). Therefore, in order to alleviate this problem,
technologies and processes that turn hazardous waste into valuable and profitable resources,
are urgently needed. CUT participated in the Interreg MED project RE-LIVE WASTE, where the
existing struvite crystallization reactor (SCR) from a previously built pilot that anaerobically
treated livestock waste, was upgraded and re-operated to convert livestock waste into highvalue commercial organo-mineral fertilizers (struvite). A series of pilot-scale struvite
crystallization experiments was first conducted utilizing ultra-filtration (UF) permeate as
starting material. Pig slurry or mixed livestock were anaerobically treated, with the digestate
effluent filtered through filter bags and UF ceramic membranes prior to struvite precipitation
in the 250-L SCR. The produced struvite precipitates were analysed for their quality
characteristics by X-Ray Diffraction (XRD), Scanning Electron Microscopy coupled with Energy
Dispersive X-ray analysis (SEM-EDX), and X-Ray Fluorescence (XRF), spectroscopic techniques.
Several analytical techniques for fertilizers were used for the determination of parameters
such as polycyclic aromatic hydrocarbons (PAHs), and hexavalent chromium (Cr6+). Struvite
precipitates from UF permeate mixed waste and pig slurry had high purity, more than 90%
w/w, based on XRD analysis using Reference Intensity Ratio method. Typical struvite
structures such as orthorhombic were observed in SEM-EDX. The precipitates complied with
the regulatory requirements for pathogens, carcinogens (PAHs, PCBs, and Cr6+), and heavy
metals (XRF) (Regulation (EU) 2019/1009). Overall, results from our pilot-scale process
unveiled that nutrient recovery from recalcitrant livestock waste is feasible, producing a highvalue solid organo-mineral fertilizer.
major cause of this problem is the disposal of inadequately treated livestock waste in soil and
water resources with adverse environmental implications1,2. Currently, the most common
manure management practice is solid-liquid separation, while a small percentage of these
waste is anaerobically digested (6.4% in EU 273
). Therefore, in order to alleviate this problem,
technologies and processes that turn hazardous waste into valuable and profitable resources,
are urgently needed. CUT participated in the Interreg MED project RE-LIVE WASTE, where the
existing struvite crystallization reactor (SCR) from a previously built pilot that anaerobically
treated livestock waste, was upgraded and re-operated to convert livestock waste into highvalue commercial organo-mineral fertilizers (struvite). A series of pilot-scale struvite
crystallization experiments was first conducted utilizing ultra-filtration (UF) permeate as
starting material. Pig slurry or mixed livestock were anaerobically treated, with the digestate
effluent filtered through filter bags and UF ceramic membranes prior to struvite precipitation
in the 250-L SCR. The produced struvite precipitates were analysed for their quality
characteristics by X-Ray Diffraction (XRD), Scanning Electron Microscopy coupled with Energy
Dispersive X-ray analysis (SEM-EDX), and X-Ray Fluorescence (XRF), spectroscopic techniques.
Several analytical techniques for fertilizers were used for the determination of parameters
such as polycyclic aromatic hydrocarbons (PAHs), and hexavalent chromium (Cr6+). Struvite
precipitates from UF permeate mixed waste and pig slurry had high purity, more than 90%
w/w, based on XRD analysis using Reference Intensity Ratio method. Typical struvite
structures such as orthorhombic were observed in SEM-EDX. The precipitates complied with
the regulatory requirements for pathogens, carcinogens (PAHs, PCBs, and Cr6+), and heavy
metals (XRF) (Regulation (EU) 2019/1009). Overall, results from our pilot-scale process
unveiled that nutrient recovery from recalcitrant livestock waste is feasible, producing a highvalue solid organo-mineral fertilizer.