Biogas residue biochar integrated with phosphate from its ash for the effective recovery of nutrients from piggery biogas slurry

Abstract Magnesium ammonium phosphate (MAP) precipitation generally requires an external phosphorus source to increase the recovery of NH 4 + -N from biogas slurry. However, P-rich piggery residue has been ignored as a source. In this study, was carbonized into biochar (BRC), followed by acid leaching synthesize functionalized BRC and release PO 3− -P its ash The effects different acids on efficiency morphological changes P in were investigated, slurry recovered with MAP precipitation. results showed that oxalic acid-hydrochloric mixed could leach more than 96% BRC, while weakening inhibitory effect Ca 2+ mainly composed inorganic P, most nonapatite IP apatite (Ca 3 (PO ) 2 leached during leaching, latter easily leached. Under optimal conditions, method had significant (96.4%) (99.3%) through chemical (forming MgPO ·H O precipitate) bonding -OH, C = C-H functional groups. final product also BRC-based slow-release N-P fertilizer rich struvite. This study solved disposal problems N-rich providing innovative technology for resource utilization faecal sewage at pig farms. Graphical