Energetic and physical properties of Moroccan biochar nutshells and their energy briquettes

The heat treatment of nutshells, followed by the densification of its biochar particles, can be used as a process to improve its quality for use as a solid fuel. In this study, Taguchi method, gray relational analysis (GRA), and analysis of variance (ANOVA) were used to elucidate the effect of compressive force, particle size, and binder content on physical properties of biochar briquettes produced from nutshells, they were also used to determine the optimum conditions of compressing the fuel briquettes. The percentage contribution of each controllable factor was also determined. The solid fuel briquettes were produced by compacting the mixture of the ground biochar and the binder (molasses) at ambient temperature, using a piston and mold process. The results showed that the obtained biochar has a good fuel quality; the amount of binder is the most influent parameter; and that the energy briquettes obtained under the optimal conditions (compressive force of 112 MPa; binder amount of 40%; particle size <200 µm) present a high density, high calorific value, and a good compressive strength.