[Mechanisms Summary and Potential Analysis of EPS as a Flame Retardant]

High value-added extracellular polymer substance (EPS) extracted from excess sludge can effectively promote resource recovery from wastewater. EPS can replace traditional alginate in the food, medicine, textile, printing and dyeing, papermaking, and household chemicals industries. Moreover, its unique performance as a flame retardant has shown attractive potential for aircraft including space shuttles. This is due to the complicated chemical structure and composition of EPS, the excellent compatibility, adhesion, and other advantages of which could yield environmental-friendly flame-retardants. Therefore, a systematic analysis and summary on the mechanisms of EPS as flame retardants is of significance for future application. On the basis of the advantages and disadvantages of other fire-resistant materials on the market, the characteristics and application potential of EPS are analyzed and summarized. Second, the possible fire-resistant mechanisms of phosphorus and alginate-like substance (ALE) in EPS are revealed, and the synergistic flame-retardant effects of extracellular-proteins are also elucidated. Based on this, the flame-retardant characteristics of EPS are comprehensively evaluated and compared with other fire-resistant materials. To further improving the performance of EPS as a flame-retardant material, some modification strategies are proposed, such as increasing their phosphorus content, purifying and enhancing the content of ALE in EPS, and optimizing the modification methods of EPS on their substrates.