the increase in world population has led to the growth in energy demand. the primary sources of this energy come from the combustion of conventional fuels, which are contributing to polluting the environment. biodiesel offers a solution as an alternative fuel for internal combustion engines, however it emits higher (nitrogen oxides) nox emission. exhaust gas recirculation (egr) systems, as well as methods that supply steam into the intake air system of diesel engines, are used to lower nox emissions. this study focuses on determining the effects of egr, methods that supply steam into the intake air systems, canola biodiesel, and emulsions consisting of diesel-biodiesel blends with additives on diesel engine performance and emissions. experiments using two modern diesel engines (a light-duty and a heavy-duty) were investigated at various operating conditions. the results showed that canola biodiesel increased fuel consumption and nox, but decreased other emissions including carbon monoxide (co) and hydrocarbon (hc) emissions. the use of both egr, methods that supply steam into the intake air system, and emulsion consisting of diesel-biodiesel blend with diethyl ether (dee) showed a significant reduction in nox emission and exhaust temperature; however, there were slight increases in fuel consumption, co, and hc emissions.