This paper investigates the feasibility of mitigating emissions from diesel engines through the combined application of alternative fuels and an unconventional catalytic converter employing cost-effective catalysts. The dwindling reserves of fossil fuels necessitate the exploration of sustainable power sources for internal combustion engines, thereby reducing our dependence on these finite resources. This study evaluated the performance parameters and emissions of a single-cylinder, four-stroke, stationary diesel engine fueled with blends of 10%, 20%, and 30% cottonseed oil in diesel (by volume). Following the identification of the optimal blend, a performance test was conducted again with the inclusion of a custom-designed and fabricated catalytic converter. Exhaust emissions were subsequently measured with and without the converter in operation. The design of the unconventional catalytic converter considered the engine's specifications, incorporating cerium oxide and sponge iron as oxidation catalysts for CO and hydrocarbon (HC) conversion. Charcoal was employed as a reduction catalyst to specifically target NOx emissions.