Binder Performance in Biochar Densification: Critical Analysis of Trade-offs between Mechanical and Energy Properties and Implications for Developing Countries

Abstract

The compaction of biochar into briquette form offers a viable method for improving the energy utilization of leftover biomasses, especially in underdeveloped nations. The intrinsically poor cohesiveness of biochar necessitates the use of binders, whose characteristics and ratios directly affect the mechanical, energy, and environmental attributes of the briquettes. This paper presents a comprehensive analysis of the primary binder types, categorized into organic, mineral, intrinsic, and hybrid classifications, alongside the relevant physicochemical mechanisms, including particle coating, hydrogen bond generation, and thermoplastic phenomena. The investigation indicates that organic binders, including molasses and starch, enhance cohesiveness and augment calorific value, although possess restrictions about their hygroscopicity. Conversely, mineral binders offer substantial mechanical strength at the cost of calorific value. Intrinsic binders, such as lignin, have intriguing possibilities but are contingent upon the conditions of implementation. Hybrid binders present a viable way to enhance these trades-offs. Ultimately, targeted recommendations are presented for Guinea, emphasizing the utilization of local resources and by-products to facilitate the advancement of sustainable solid fuels.