Characteristics of Briquette as an Alternative Fuel Made of Mixed-Biomass Waste (Dairy Sludge and Coconut Shell)

Coal is used mainly in boiler units as a heat energy generator. The non-renewable nature of coal encourages creating alternative fuels, such as briquettes. The abundance of organic material in dairy sludge has potentially becomes briquettes. To improve the quality of the briquettes, it is necessary to add other biomass with high caloric value, such as coal and coconut shell. Dairy sludge and coconut shell will undergo pyrolysis to produce charcoal later mixed with the coal. The formulation was determined using linear programming, with the decision variables consisting of coal (X1), dairy sludge charcoal (X2), coconut shell charcoal (X3), and binder (X4). The purpose of linear programming is to maximize the heating value of the briquettes and obtain proximate characteristics that suit Indonesian National Standard (SNI 01-6235-2000) for wood charcoal briquettes. The charcoal yield from pyrolysis was 44.35% for dairy sludge and 27.8% for coconut shell charcoal. The optimal briquette formulation was 10% coal, 10% dairy sludge charcoal, 75% coconut shell charcoal, and 5% adhesive. The calorific value obtained reached 9247.41 cal/gram. However, the ash content did not meet the SNI 01-6235-2000.