Extraction and characterization of coffee husk biodiesel and investigation of its effect on performance, combustion, and emission characteristics in a diesel engine

Abstract

Biodiesel and its blends with diesel are used in engines to overcome the problems of environmental pollution and fast depletion of conventional fuels. The purpose of this research is to extract oil from coffee husk, convert it into coffee husk oil methyl ester (CHOME) by transesterification, and test the suitability of this biodiesel as an alternate, renewable, sustainable fuel for a diesel engine. The physicochemical characteristics of the developed biodiesel are studied and compared with regular diesel. The results showed that the fundamental properties of the produced fuel are comparable to that of diesel. The performance, combustion, and emission characteristics of a diesel engine fueled with CHOME biodiesel are investigated. The experiments are conducted in a single-cylinder direct injection diesel engine at a constant speed by varying the loads (0, 25, 50, 75, and 100%) for different biodiesel-diesel blends (B10, B20, B30, B40, B50, and B80), and the results are compared with the baseline diesel. The brake thermal efficiency (BTE) of the blends, B10, B20, B30, and B50 dropped by 0.6, 0.7, 1.29, and 3%, respectively compared with the neat diesel. Similarly the brake specific energy consumption (BSEC) is reduced by 0.1, 0.3, 0.44, and 0.77% for B10, B20, B30, and B50, respectively. Exhaust gas emissions are reduced for all biodiesel-diesel blends. Compared to regular diesel, at full load, CO, HC, and smoke opacity of B30 reduced by 13.2%, 4%, and 12%, respectively. CO2 of B30 at full load is increased by 8.63%. In general, it can be stated that CHOME biodiesel is a promising alternate biodiesel that can be used in an internal combustion engine without major modifications.