Ammonia Air Stripping from Different Livestock Effluents Prior to and after Anaerobic Digestion

Ester Scotto di Perta (), Raffaele Grieco, Stefano Papirio, Giovanni Esposito, Elena Cervelli, Marco Bovo and Stefania Pindozzi
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Ester Scotto di Perta: Department of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Italy
Raffaele Grieco: Department of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Italy
Stefano Papirio: Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, 80125 Naples, Italy
Giovanni Esposito: Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, 80125 Naples, Italy
Elena Cervelli: Department of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Italy
Marco Bovo: Department of Agricultural and Food Sciences, University of Bologna, 40127 Bologna, Italy
Stefania Pindozzi: Department of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Italy

Sustainability, 2023, vol. 15, issue 12, 1-10

Abstract: Livestock digestate provides nutrients and organic matter to the soil while increasing agricultural sustainability. Nevertheless, nitrogen (N) losses due to the nutrient surplus in regions characterized by intensive animal farming activities still represent an unsolved issue. For this purpose, digestate needs proper treatment and management to avoid N losses in the environment. In the livestock farming context, anaerobic digestion (AD) can be accompanied by an ammonia stripping (AS) process for N recovery. This paper aims to investigate the feasibility AS prior to and after AD of the manure, focusing on two different livestock farms, representative of dairy cattle and pig breeding in southern Italy. AS was performed at a lab scale by injecting microbubbles of air, which allowed the pH to increase, and thus the removal of ammonia. The results show that treating a dairy raw slurry with high intermediate alkalinity (IA) (6707 mg CaCO 3 L −1 ) with AS may not be convenient in terms of total ammonia nitrogen (TAN) reduction. As a matter of fact, the loss of buffering capacity during the stripping process resulted in a pH never exceeding the value of 9, which could not promote free ammonia volatilization, whereas integrating AD with AS allowed us to obtain a 34% higher TAN reduction under the same stripping conditions at a temperature (T) of 38 °C and a gas-to-liquid ratio (G/L) of 1:1. Therefore, the AS removal efficiency strongly depends on the characteristics (mainly IA) of the treated matrix. High IA values suggest a possible high concentration of volatile fatty acids, which hinders pH increases and, thus, enables ammonia stripping. Despite the initial matrix origin, a low IA compared to the total alkalinity (TA) (<20% of TA) ensures a greater ammonia removal efficiency, which could be similar between digestate and raw manure in the same operative process conditions. Nonetheless, the amount of ammonia stripped is related to the initial TAN concentration of the specific matrix.

Keywords: ammonia stripping; nitrogen recovery; anaerobic digestion; digestate; manure management (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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