Insight into transformation of phosphorus species in biomass gasification at different stages

Amid growing concerns over global phosphorus scarcity and the shift toward gas-biochar co-production, biomass gasification offers a promising route for phosphorus recovery. This study investigated phosphorus transformation across the pyrolysis, reduction, and oxidation stages of gasification, which involves complex thermal and atmospheric shifts. The findings revealed that during the high-temperature pyrolysis stage, phosphorus mineralization was initiated, leading to a rapid increase in both inorganic phosphorus and total phosphorus content in the biochar. In the reduction stage, the proportion of metaphosphate increased significantly, reaching 60%, indicating that the strongly reducing atmosphere promoted the polymerization transformation of phosphorus. In the oxidation stage, the phosphorus recovery rate decreased, and with increasing oxidation temperature, phosphorus gradually transformed into more stable forms, particularly hydrochloric acid-extractable phosphorus and residual phosphorus. This study reveals new pathways for phosphorus transformation during biomass gasification, providing a theoretical foundation for gas-char co-production in gasification technology.