Reduced smoke and nitrogen oxide emissions during low-temperature combustion of ethanol and waste cooking oil

Air pollution is a major issue affecting the health of millions of citizens, notably in cities where pollutants are concentrated. Low-temperature combustion is a promising route to reduce nitrogen oxides and smoke emissions from compression ignition engines. Reduction in emissions during low-temperature combustion is known, yet emissions using oxygenated biofuels are poorly known. Therefore, I tested the potential reduction in emissions using oxygenated biofuels during low-temperature combustion, in the reactivity-controlled compression ignition mode. Ethanol, a low-reactivity fuel, was inducted in the intake manifold at 10% and 20% levels on energy basis, whereas waste cooking oil biodiesel, a high-reactivity fuel, was injected directly inside the cylinder. Results show a reduction in emission of nitrogen oxides up to 60%, and of smoke up to 29%. Nonetheless, unburned hydrocarbons and carbon monoxide emissions increased up to 2% at full load for biodiesel with 20% ethanol induction, compared to neat diesel and biodiesel.