A Comparison of Diesel and Biodiesel Emissions Using Dimethyl Carbonate as an Oxygenated Additive

Diesel vehicles account for the majority of new vehicles sales in Europe. This is due to inherent fuel efficiency and high reliability. Global warming concerns have seen demand for renewable alternatives to fossil diesel with low carbon dioxide (CO2) producing emissions. Oxygenated biodiesel fuels such as rapeseed methyl ester (RME) can be utilized in an unmodified conventional diesel engine. RME combustion produces low emissions of unburnt total hydrocarbons (THCs), carbon monoxide (CO), and particulate matter (PM). This is due in part to fuel-born oxygen content (10.8% wt). This study examines the effect of adding fuel-born oxygen in the form of dimethyl carbonate (DMC) (a nontoxic potentially bioderived 53.3% wt oxygenated additive) to conventional pump diesel. It was found that nitrogen oxides (NOx) increased and that THCs, CO, and PM were reduced by up to 50% with a 96% diesel, 4% DMC blend. Interestingly 2% DMC in diesel can generate comparable particulate, THCs and CO emissions to RME combustion, at just 1.1% wt oxygen. A DMC blend may also have potential in the reduction of as yet unregulated carcinogenic emissions such as benzene and 1,3-butadiene.