Enhanced phosphorus recovery from biogas digestate is crucial for sustainable agriculture. This study, published in Bioresource Technology, reveals that metal salts recover up to 65% of phosphorus, outperforming modified biochar’s 52%. This efficiency improves nutrient management and reduces environmental impact by concentrating phosphorus, which facilitates easier transport and use in fertilizers.  

Phosphorus (P) is a critical resource for global agriculture, but its reserves are dwindling. In a study published in Bioresource Technology, Naga Sai Tejaswi Uppuluri, Xueling Ran, and colleagues explored enhanced P recovery from biogas digestate, a byproduct of anaerobic digestion, using modified biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More and metal salts. Their research highlights the potential of these methods to transform digestate management in agriculture, making it more sustainable and environmentally friendly.  

In this study, the researchers explored using magnesium (Mg2+) and calcium (Ca2+) modified biochar, along with metal salts, to enhance P recovery. Modified biochar increased P recovery to 52%, a notable improvement compared to the control’s 35%. However, metal salts (kieserite and CaCl2​) outperformed biochar, achieving an impressive 65% P recovery.  

The enhanced P recovery is attributed to adsorption, ion exchange, and precipitation. Metal ions in the salts react with phosphate in digestate, forming precipitates and increasing P concentration in the solid phase. While metal salts offer superior P recovery, biochar improves soil health by enhancing water retention and nutrient availability.  

These findings suggest that both modified biochar and metal salts are effective in enhancing P recovery from digestate, with metal salts demonstrating higher efficiency. The study contributes valuable insights for developing sustainable agricultural practices and improving nutrient management in biogas plants. Further research is needed to optimize these methods for industrial applications and assess their long-term environmental and economic viability.  

SOURCE: Uppuluri, N. S. T., Ran, X., Guo, J., & Müller, J. (2025). Enhanced phosphorus recovery from digestate via solid-liquid separation using Mg2+ and Ca2+ modified biochar. Bioresource Technology, 427, 132409.