Potential impact of microbial corrosion on torrefied biochar for solid biofuel utilization: A critical review

Torrefied biochar, a promising solid biofuel produced via moderate thermal biomass processing, enhances energy density and hydrophobicity but remains vulnerable to microbial degradation under humid, warm storage conditions. This review explores the mechanisms and risks of microbial corrosion, emphasizing the roles of bacteria, fungi, and actinomycetes in biochar deterioration through enzymatic breakdown, acid production, and biofilm formation. Feedstock composition, particularly lignin and mineral content, and environmental parameters critically influence microbial activity. This study evaluates sterilization strategies including hydrogen peroxide, ultraviolet irradiation, and potassium permanganate, revealing varied efficacy in suppressing microbial colonization. Optimized storage conditions and surface modifications are recommended for long-term preservation. Findings highlight the importance of integrated biological and environmental control strategies to maintain fuel properties, mitigate emissions, and support biochar's role in carbon-neutral energy systems. This review provides a systematic framework for improving biochar stability and advancing its industrial application.