The use of Biodiesel in a conventional diesel engine results in substantial reduction of unburned hydrocarbons, carbon monoxide, and particulate matter compared to emissions from petroleum diesel fuel.
In addition, the exhaust emissions of sulphur oxides and sulphates (major components of acid rain) from Biodiesel are essentially eliminated compared to petroleum diesel.
Of the major exhaust pollutants, both unburned hydrocarbons and nitrogen oxides are ozone or smog forming precursors. The use of Biodiesel results in a substantial reduction of unburned hydrocarbons.
Emissions of nitrogen oxides are either slightly reduced or slightly increased depending on the duty cycle of the engine and testing methods used. Based on engine testing using the most stringent emissions testing protocols required by EPA for certification of fuels or fuel additives in the US, the overall ozone forming potential of the hydrocarbon emissions from Biodiesel was nearly 50 percent less than that measured for diesel fuel.