Abstract
Most of the population of Ethiopia, like that of other Sub-Saharan African countries, depends on traditional biomass for cooking and baking food. Most rural people in the country have no access to electricity and the price of fossil fuel is increasing in alarming rate. On the other hand there are large amounts of coffee husks in coffee growing areas which are left unused. In most cases, they are either left in the fields or burning in open air and this causes severe environmental problems.
A comprehensive study was carried out in Dilla town, a representative coffee growing area of the country, to assess the potential of coffee husks for production of briquettes to be used as a source of household energy. The amount of coffee husk produced in the town was assessed and briquettes were prepared with different carbonized coffee husk with different particle size using clay soil as a binder. The briquettes were characterized following ASTM procedure. The result showed that an average of 57,700.96 tone coffee husk is produced in the town every year. The coffee husk in the town is mostly used as fertilizer and traditional source of fuel. There was no proper way of coffee waste management to controlling environmental pollution. The extent of simple dumping of coffee husk were 83.4%, 90% and 80% in chichu, Sisota and Gola kebeles, respectively The minimum average LHV of the produced briquettes from coffee husk (dry process) as a factor of different particle size and charcoal to clay soil binder ratio was 17.7MJ/kg. The mean average value for fixed carbon content(FCC) and calorific value of the briquettes (particle size 1mm, 3.35mm, 5.60mm, and charcoal to binder ratio of 3:1, 4:1 and 5:1) were: 55.95±0.99 % and18.1±0.4 (MJ/kg); 48.17±3.24 % and 17.7±0.1 (MJ/kg );48.07±4.18% and 17.47±0.65(MJ/kg) and 47.85±3.27& 17.12%±0.26(MJ/kg); 49.92±3.05% &17.27 ±0.37(MJ/kg) and 52.76±1.53 &18.54±0.45(MJ/kg) respectively. The result showed that the calorific value of the raw material was lower than the briquettes produced in all the cases. Briquettes produced from higher charcoal to binder ratio was having the highest calorific value while briquettes produced from higher particle size observed to have the lowest calorific value. In general, coffee husk found to have better physicochemical properties as compared to other agricultural residues, especially in calorific value. Therefore, the use of coffee husk for briquette making to be used as a source fuel has to be considered in coffee growing areas. Further studies should be conducted regarding the effect of different varieties of coffee species and conditional/ environmental impact on the calorific value/ heat energy of briquettes produced from coffee husks.
Key words: biomass, briquette,briquetting,charcoal, coffee husk,fuel quality,