Performance and emission evaluation of diesel engines using Karanja biodiesel blended with diethyl carbonate

• Experimental assessment of Karanja biodiesel with the addition of Diethyl Carbonate (DEC) in a CI engine. • DEC addition (maximum 10 %) enhanced BTE by 6.5 % and cut down NOx, CO, HC, and smoke emissions considerably. • Carbon credit and fuel economy analysis demonstrate environmental and economic potential of DEC-blended biodiesel. This research investigates the application of Diethyl Carbonate (DEC) as an oxygenated additive in Karanja biodiesel (B20) fuel blends to promote combustion performance and decrease emissions in a compression ignition engine. Different from frequently researched additives like DEE, ethanol, or DMC, DEC possesses a special set of characteristics with high cetane number, high oxygen content, and low volatility, promoting complete combustion with lower peak flame temperatures. Experimental findings revealed that a 10 % DEC blend provided 6.5 % better brake thermal efficiency and 7.8 % lower BSFC than B20. NOx, CO, HC, and smoke emissions reduced by 13 %, 29.8 %, 24.5 %, and 42.5 %, respectively. These gains indicate that DEC does not only avoid the common NOx–particulate trade-off but also maximizes fuel economy without sacrificing engine operation. An initial carbon footprint analysis approximated a yearly CO₂ savings of 382.22 kg per engine. Although this is indicative of future carbon credit possibilities, techno-economic evaluation at a scale is needed to assess full-scale viability. On the whole, the results suggest that DEC-upgraded biodiesel blends provide a promising avenue toward stricter emissions compliance and greater adoption of sustainable biofuels.