Manure digestate storage under different conditions: Chemical characteristics and contaminant residuals

In this study, chemical characteristics and contaminant residuals in livestock manure digestate were investigated during storage under different conditions. Results show that storing digestate openly under the mesophilic condition (30 ± 1 °C) led to water evaporation and thus considerable mass reduction. As a result, concentrative effect occurred to increase the contents of organic matter, nutrients, and heavy metals during digestate storage. By contrast, ammonium (NH₄⁺) concentration in digestate decreased over storage period. The concentrative effect and NH₄⁺ reduction could be mitigated by storing digestate with coverage and/or under psychrophilic conditions (e.g. 15 ± 1 °C). Regardless of storage conditions, organic matter was further biodegraded, thereby reducing the residuals of antibiotics in digestate. Antibiotic removal was more notable when digestate was stored under mesophilic conditions. Nevertheless, additional processes to control heavy metals and antibiotics in digestate are still necessary before agricultural applications.