Emission characteristics and efficiency impacts of waste pig fat oil biodiesel in CI engine operation

In this work, the influence of the waste pig fat-based biodiesel in the diesel fuel on the emission profiles and performance characteristics of a compression-ignition engine is investigated. At a fixed 25% load, tests were performed with engine speeds extending from 800 to 1400 r/min. The emission profiles such as CO, hydrocarbon, CO 2 , NO x , and smoke opacity, along with the evaluation of brake-specific fuel consumption and brake thermal efficiency in dual-fuel operation, were considered important aspects of this investigation. At an engine load of 25% and a rotational speed of 800–1400 r/min, the increase of waste pig fat biodiesel percentage resulted in a remarkable decrease of CO, hydrocarbon, and smoke opacity emissions. B80 decreased the CO emission from 0.37% to 0.21% (diesel: 0.75% to 0.43%) and the hydrocarbon emission from 34 to 19 ppm (diesel: 55 to 34 ppm). Also, the smoke opacity was reduced from 11% to 4.5% for B80 and for diesel from 14.5% to 8.5%. However, CO 2 concentrations were increased from 0.85 to 1.94% with increasing biodiesel content, as also NO x concentrations from 99 to 312 ppm. The engine performance was deteriorated with an increase in brake specific fuel consumption from 3.94 to 5.42 kg/kWh and a decrease in brake thermal efficiency from 24.2% for diesel to 17.82% for the B80 blend. After weighting among these competing factors, B20 is the best compromise, in that it offers a good balance of substantial reductions in CO, hydrocarbons, and smoke emissions, with moderate increases in NO x and decreases in efficiency that are acceptable for non-tempered engines.