This paper describes the process of extracting ethanol from Jatropha curcas and its various blending effects on spark-ignited engine performance for environmental sustainability. Alternatives to conventional fuel sources have to be found because of the depletion of fossil fuels and stringent regulations. Every day, the growing population and improved transportation increase the energy demand. Bioethanol is an effective substitute for gasoline and SI engine diesel. Worldwide, passenger cars typically blend 10% bioethanol with gasoline. Some nations, like India, have stated plans to blend 20% bioethanol with gasoline starting shortly. From leftover jatropha deoiled cake (JDC), bioethanol was produced utilizing the fermentation and vacuum distillation methods. Four different blends were prepared on a volumetric basis at different engine speeds at a constant compression ratio of 10:1 and the wide-open throttle was tested for various performances and emissions. Bioethanol enrichments reduce CO and CO2 emissions but increase nitrogen oxide emissions. JDCE 15 was found to have the best engine performance out of all the fuel blends tested. This study suggests that, if NOx emission reduction measures are carried out, JDC can be used as a source for the manufacturing of second-generation bioethanol. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.