Ammonia recovery from food waste digestate using solar heat-assisted stripping-absorption. (15th July 2020)

• Record Type: Journal Article
• Authors: Melgaço, Lucas A.O.; Meers, Erik; Mota, César R.
• Is Part Of: Waste management. Volume 113(2020)
• Page Start: 244
• Page End: 250
• Publication Date: 2020-07-15
• Subjects: Nitrogen recovery -- Food waste -- Stripping-absorption -- Anaerobic digestate; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2020.05.047
• Languages: English
• ISSNs: 0956-053X

Abstract

Highlights: A system with solar heating was tested to recover N from food waste digestate. Solar heater was able to keep operation temperature at 45 °C. High ammonia removal (98%) was achieved at 45 °C without chemical pH adjustment. System recovered N as ammonium sulphate crystals that could be used as fertilizer. Proposed system could be a viable option for NH3 recovery in developing countries. Abstract: The highest costs of stripping-absorption processes for ammonia recovery are related to energy (for heating and air supply) and chemical addition (for pH adjustment). In this paper, a simplified system that used no chemicals, and a renewable source of energy for heating, was tested to recover nitrogen as ammonium sulfate from food waste digestate. pH adjustment was achieved by CO2 stripping, and vacuum tube solar collectors were used to provide heating. The effect of different temperatures (25 °C and 45 °C) and gas to liquid ratios (1700 and 2600) on ammonia removal and recovery were assessed. Ammonia removal efficiencies higher than 91% were achieved for all evaluated experimental conditions. The solar heater showed adequate capacity to increase the temperature of the liquid digestate by 21 °C and maintain the temperature at 45 °C throughout the experiment. Tests carried out at 45 °C achieved the highest ammonia removal efficiency (98%) at the lowest evaluated G/L ratio (1700). Better absorption efficiencies could potentially have been achieved if lower inlet airflow rates and packing material had been used in the absorption column.