Unregulated emissions from oxygenated fuels

Before proposing newer fuels for combustion engines, it is imperative to determine the potential emission advantages or liabilities of these fuels. Considerable research work and legislation concerning the regulated emissions from newer proposed fuels are covered in the literature. However, the emphasis on reducing the unregulated emissions (aromatic hydrocarbons, carbonyl compounds, etc.) is minimal, even though there are severe health hazards associated with them. The regulated emissions such as carbon monoxide and NOx are somehow countered by various natural processes (carbon dioxide cycle, nitrogen cycle, etc.). There is no well-known natural process that helps to balance the unregulated emissions. Oxygenated fuels have been continuously recognized as a clean, sustainable, and renewable feedstock for combustion engines by the research community. Oxygenated fuels help to reduce the particulate matter and other regulated emissions significantly. However, knowledge about the unregulated emissions from the combustion of these fuels in combustion engines is limited and inconsistent. Therefore the present study aims at analyzing and consolidating the existing knowledge on emissions of carbonyl, aromatic hydrocarbons, and their derivatives from oxygenated fuels.