Energy Evaluation of Various Compositions of Biomass Waste Briquettes

This study focused on evaluation of energy values and performance of briquettes prepared from biomass wastes such as sawdust, rice husk and their composites using two binders (starch and clay) when fired in briquette stove. The briquettes produced are composed of locally sourced bio-wastes of uniform grain sizes (0.5 mm) and two binders in percentage composition of 90:10 which were sun-dried, prepared and compressed. Combustion-related properties (%volatile matter, % ash content, % fixed carbon and calorific value of raw materials) were determined for the sample materials (sawdust, rice husk and starch). Performance tests on 12 different briquettes which included water boiling time, burning time, ignition time, heating rate, fuel consumption rate and cooking efficiency test were carried out. The briquettes were subjected to energy evaluation tests using a bomb Calorimeter. The mean bulk densities of the briquettes produced from the different samples were determined. The test results show that the calorific value of mahogany sawdust, gmelina, oak, composite of mahogany/gmelina/oak, rice husk and gmelina/rice husk briquettes with binder starch were 4.516 kcal/g, 4.1487 kcal/g, 4.4312 kcal/g, 3.8614 kcal/g, 4.0531 kcal/g, 4.067 kcal/g respectively and with clay as binder were 1.9003 kcal/g, 1.5331 kcal/g, 1.8156 kcal/g, 1.2458 kcal/g, 1.4375 kcal/g, 1.4451 kcal/g respectively. The ignition time of 0.206 min, boiling time of 18.1 min, fuel consumption rate of 33.2 g/min and burning time of 42.21 min of mahogany briquette with starch binder is less than the values obtained for other briquettes while its cooking efficiency of 45.8% is greater than those of other briquettes. This therefore shows that it has better energy efficiency than other briquettes considered.