Taguchi-optimized ammonia stripping for high-efficiency mascagnite recovery from anaerobic digestate in a circular economy
Bioresource Technology Reports, vol.35, 2026 (ESCI, Scopus)
- Publication Type: Article / Article
- Volume: 35
- Publication Date: 2026
- Doi Number: 10.1016/j.biteb.2026.102995
- Journal Name: Bioresource Technology Reports
- Journal Indexes: Emerging Sources Citation Index (ESCI), Scopus
- Keywords: Absorption, ammonia stripping, Digestate, Experimental design, Taguchi
- Yıldız Technical University Affiliated: Yes
Abstract
The valorization of nitrogen-rich anaerobic digestate is pivotal for advancing circular bioeconomy frameworks. This study presents a systematically optimized, high-efficiency protocol for upcycling liquid digestate into agricultural-grade Mascagnite ((NH4)2SO4) via integrated air stripping and stoichiometric acid absorption. A Taguchi L16 orthogonal array was employed to investigate the complex mass transfer dynamics governed by pH, temperature, air flow rate, and stripping time. Analysis of Variance (ANOVA) revealed that hydrodynamics, specifically air flow rate, is the dominant process driver (60.1% contribution), highlighting severe liquid-side mass transfer limitations in viscous digestate matrices. Consequently, thermodynamic and hydrodynamic enhancement proved more critical than extreme alkalinization (pH contribution: 13.7%). Under the statistically validated optimal conditions (pH 10.5, 50 °C, 8 L/min, 3 h), the system achieved a confirmed ammonia removal efficiency of 98.3%. Downstream acid absorption resulted in a 97.0% recovery yield of solid crystalline fertilizer. Advanced structural and elemental characterizations (XRD, SEM-EDS) definitively identified the recovered phase as orthorhombic Mascagnite, exhibiting high chemical stability and purity indistinguishable from analytical-grade standards. This approach successfully transforms a waste liability into a premium mineral commodity, mitigating environmental pollution while closing the agricultural nutrient loop.