NOx emissions of biodiesel as an alternative diesel fuel

As an environmental friendly alternative fuel for compression-ignition (diesel) engines, fatty acid alkyl monoesters, commonly known as biodiesel, are produced from renewable feedstocks Such as vegetable oils and animal fats. Without engine modification, when a diesel engine is fuelled with biodiesel, it provides significant reductions in particulate matter, carbon monoxide and unburned hydrocarbons compared with petroleum-based diesel fuel. In contrast to these reductions, many studies show that the use of biodiesel increases NOx emissions, while only a few papers have reported no changes or reduction in NOx emissions. Various arguments have been used in the literature to explain the increase in NOx emissions when biodiesel is used. This study discusses the combustion characteristics of biodiesel and its fuel properties which are effective in the NOx formation.