Investigations into Physical and Fuel Characteristics of Briquettes Produced from Cassava and Yam Peels

Abstract

Globally, 140 billion metric tons of biomass is generated every year from agriculture. This volume of biomass can be converted to an enormous amount of energy and raw materials. These residues are usually dumped and flared on the farms, where they constitute health risk to both human and ecology. Densification of these residues would improve their bulk handling, transportation and storage properties. Therefore, this work investigated densification characteristics of cassava and yam peels using an experimental briquetting machine.

The ASAE standard methods were used to determine the moisture contents (dry basis) and densities of the milled residues and briquettes, while ASTM standard methods were used to determine the proximate and ultimate analyses of the residues. The initial, maximum and relaxed densities were also determined using ASAE standard methods. Also evaluated were compaction, density and relaxation ratios of the briquettes. The mechanical properties were determined using universal testing machine, while the heating value was determined using Ballistic Bomb calorimeter. The mean moisture contents of cassava and yam peels residues were 10.19% and 9.27% respectively, while those of relaxed briquettes were 8.76% and 7.95% respectively.  The initial, maximum and relaxed densities were 251.50 kg/m³; 741.13 kg/m³ and 386.4 kg/m³ respectively for briquettes produced from cassava peel, while the corresponding values for briquettes produced from yam peel were 283.40 kg/m³; 911.45 kg/m³ and 512.54 kg/m³ respectively. The compaction ratio of 2.94 and 3.21 were obtained for briquettes produced from cassava and yam peels respectively. The compressive strength of briquette from cassava peel was 1.53kN/m² (SD 0.05), while that of yam peel was 1.76kN/m² (SD 0.04). The higher heating value of briquettes from cassava peel was found to be 12,765kJ/kg (SD 30), while the corresponding value for yam peel was 17,348kJ/kg (SD 20). The results of this work indicate that briquettes produced from the two biomass residues would make good biomass fuels. However, findings show that yam peel briquette has more positive attributes of biomass fuel than its cassava peel counterpart. It has a moderate moisture content of 10.95 %, higher density of 911.45 kg/m³ and lower relaxation ratio of 1.78. Other positive attributes of yam peel briquette over cassava peel are long after glow time of 375 secs and slow propagation rate of 0.16 cm/s. It also has higher heating value of 17,348 kJ/kg and compressive strength of 1.76 kN/m² compared to cassava peel, which are 12,765 kJ/kg and 1.53 kN/m² respectively.

Keywords: agricultural wastes, briquette, briquetting machine, cassava peel, yam peel,