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Direct nitrogen stripping and upcycling from anaerobic digestate during conversion of cheese whey into single cell
Silvio Matassa1, Vincenzo Pelagalli2, Stefano Papirio3
1Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, via Claudio 21, 80125 Naples, Italy; Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, via G. di Biasio 43, 03043 Cassino, Italy.
Abstract:
The environmental impact of the dairy industry is heavily influenced by the overproduction of nitrogen- and carbon-rich effluents. The present study proposes an innovative process to recover waste contaminated nitrogen from anaerobic digestate while treating excess cheese whey (CW) and producing high-quality, clean single cell protein (SCP). By relying on direct aeration stripping techniques, employing an airflow subsequently used in the aerobic cheese whey fermentation step, the investigated process was able to strip 41-80% of the total ammonium nitrogen (N-NH4+) from liquid digestate. The stripped ammonia gas (NH3) was completely recovered as N-NH4+ in the acidic CW, and further upcycled into SCP having a total protein content of 74.7% and a balanced amino acids profile. A preliminary techno-economic analysis revealed the potential to directly recover and upcycle nitrogen into SCP at costs (4.3-6.3 €·kgN-1) and energetic inputs (90-132 MJ·kgN-1) matching those of conventional feed and nitrogen management processes.
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