Biochar in Fire protection: A sustainable alternative to other flame retardants and synergists

Biochar (BC), derived from the thermo-chemical conversion of waste organic materials like coffee grounds and sewage sludge, offers a sustainable alternative to conventional flame retardants [1-3]. Biochar’s unique properties, such as high thermal stability and charring behavior, make it an effective component in fire-safe polymeric systems like coatings, composites, and textiles. In particular, by incorporating biochar into epoxy resins, significant improvements in fire protection, such as a UL 94 V0 rating, were achieved in vertical flame spread tests (Figure 1). Coffee-derived biochar, when combined with ammonium polyphosphate (APP) and a sol-gel Si-Ti-Mg mixed oxide, reduced peak heat release rate and total smoke production by 65 and 11 %, respectively [2]. Similarly, biochar from hydrothermal liquefaction of civil sewage sludges, when combined with other additives (e.g., APP and urea), produced self-extinguishing composites with V0 rating [3]. These materials demonstrated strong flame retardancy, primarily due to the formation of a stable char and reduced smoke emission. Future research efforts will focus on optimizing biochar properties and integrating it into bioplastics or recycled polymers for a wider application toward the design of sustainable, fire-safe materials.