Optimizing Ammonia Recovery from Biogas Digestate Using Air Stripping: Experimental and Simulation Insights for Sustainable Waste Management

The research aimed to determine the effectiveness of an ammonia recovery process through air stripping within biogas digestate. In the first step, the chicken manure was treated to volatilize the nitrogen in the form of ammonia, and then the resulting anaerobic centrate was stripped. Experimental tests and simulations with Aspen Plus were performed in order to understand the effect of temperature, flow rate, and pH on the ammonia as well as total nitrogen concentrations in the effluents.The results demonstrated that temperature, airflow rate, and pH had a significant influence on the ammonia stripping efficiency. Increasing the temperature from 30°C to 90°C improved the ammonium reduction from 80% to 93%, while increasing the airflow rate from 500 to 3000 kg/h enhanced the ammonium reduction from 75% to 97%. The pH had the most pronounced effect, with ammonium reduction increasing from 25% at pH 7.0 to 97% at pH 9.5.The Aspen Plus simulation model accurately predicted the experimental results, with a mean absolute percentage error below 3%. The model revealed the synergistic effects of pH and temperature, with optimal operating conditions identified at pH 9.0-9.5 and temperatures of 80-90°C. The results have proved to be helpful in the construction and improvement of how biogas digestate ammonia recovery systems are designed and built as well as the production of commercially valuable fertilizers whilst reducing the environmental pollution caused by nitrogen waste streams.