Monitoring the Dynamics in Nitrogen and Phosphorus Contents during Aerobic Digestion of Swine Slurry

Abstract

This study aimed to monitor the changes in the content and types of nitrogen (N) and phosphorus (P) in swine slurry (SS) across three aerobic digestion processes in public livestock recycling centers. In total, 148 swine slurry samples, including raw swine slurry from the three digestion cells, were collected from 37 livestock recycling centers around Korea from early April to mid-July 2020. The physical and chemical characteristics including the total N and P and various types of N and P of the samples were determined. The contents of organic N and P were calculated as the difference between the total and mineral components of N and P. The results showed that solid separation and aerobic digestion of SS significantly reduced the amount of the total N in the effluent by almost 70.1%, but only reduced the total P by 0.17%, resulting in a significant reduction of available N and a very high P:N ratio. This study confirmed that continuous application of composted liquid swine slurry based on N content may lead to the overapplication of P. Therefore, further research is needed to improve the N content and lower the high P:N ratios.