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Experimental investigation has been carried out to utilize biogas as an alternative source of energy in compression ignition (CI) engine under dual fuel operational mode. Biogas was inducted into the inlet manifold at different flow rates along with fresh air through inlet manifold and diesel was injected as a pilot fuel to initiate combustion under dual fuel mode. The engine performance and emission characteristics of dual fuel operational mode were analyzed at different biogas flow rates and compared with baseline conventional diesel fuel. Based upon the improved performance and lower emission characteristics under the dual fuel operation, the optimum flow rate of biogas was observed to be 2.2 kg/h. The lower brake thermal efficiency (BTE) and higher brake-specific energy consumption (BSEC) were noticed with biogas-diesel fuel under dual fuel mode when compared with neat diesel operation. Test results showed reduced NO emissions and smoke opacity level in the exhaust tailpipe emissions. However, higher hydrocarbon (HC) and carbon monoxide (CO) emissions were noticed under dual fuel mode at entire engine loads when compared with baseline fossil petro-diesel. Hence, the use of low-cost gaseous fuel such as biogas would be an economically viable proposition to address the current and future problems of energy scarcity and associated environmental concerns.

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Aim :Methodology : Results : Interpretation :Biodiesel is an attractive fuel option for diesel engines in view of issues related to fossil fuel crisis and environmental degradation. The present study aimed to prepare biodiesel from non-edible grade castor oil and to evaluate the emission characteristics of castor biodiesel fuelled diesel engine at different engine operating loads.The biodiesel was prepared from non-edible grade castor oil by single step alkaline transesterification process at room temperature.The fuel properties like kinematic viscosity, density, calorific value, flash point, pour point, and cloud point were measured as per ASTM D-6751 specifications.The engine used for experimental work is a single cylinder, four stroke, constant speed, direct injection diesel engine. The engine testing was performed at different engine loads (0.9, 1.8 and 2.7 bmep) and at constant speed of 1500 rpm with different tested fuel blends B0, B20, B40 and B60. The emission parameters like nitrogen oxides, hydrocarbons and carbon monoxide were evaluated using flue gas analyzer.Production yield of 96.5% was obtained using biodiesel synthesis and castor oil based biodiesel was found to possess similar fuel properties when compared to fossil petro-diesel. At full engine load condition of 2.7 bmep, the hydrocarbon emission was lowered by 24.6, 39.6 and 42.1% for B20, B40 and B60 fuels, respectively, and the carbon monoxide emission was reduced by 12.9, 17.1 and 26.2% for tested fuel blends B20, B40 and B60, respectively, when compared to petro-diesel.At 2.7 bmep load condition, the NO emissions was higher by 28.2% for B60 fuel when compared to petro-diesel, while, at 0.9 bmep load condition, NO emissions increased by 11.8 and 15.1% for B20 and B40 blends, respectively, when compared with petro-diesel.The non-edible grade of castor oil can be used as a raw material for biodiesel production and its blend with diesel is a suitable fuel candidate for use in diesel engine without modifications, which results in overall low emissions.i.e.