Impacts of biodiesel blends on PM2.5, particle number and size distribution, and elemental/organic carbon from nonroad diesel generators

• The effects of biodiesel and engine load on PM2.5, PN and size distribution, and EC/OC were investigated.
• Very different patterns have been observed between emissions and emission factors under various engine load conditions.
• Impact of biodiesel on emission depends strongly on engine type and varied under load.
• Biodiesel generally produce reduced emissions compared to diesel but higher PN has been observed with biodiesel.

As an important alternative to diesel fuel, biodiesel is considered sustainable and environmentally friendly and has attracted increased interest over the last few decades. For the evaluation of biodiesel’s impact on engine performance and emissions, most studies have focused on diesel vehicles and on-road diesel engines. There is also limited data available to assess the effect of biodiesels on emissions of unregulated pollutants, such as ultrafine particulate (UFP), particle number (PN) and size distributions. For developing successful emission control strategies, an understanding of biodiesel impact on emissions from both on-road and nonroad diesel engines is necessary. In this study, two nonroad diesel generators were tested with diesel and two biodiesel blends with 5% (v/v) (B5) and 20% (v/v) (B20) biodiesel under varied engine load conditions. The effects of engine load and biodiesel blends on emissions (g/min) and emission factor (g/kW h) of PM2.5, PN, elemental and organic carbon (EC/OC), as well as particle size distribution were investigated. A method for the determination of EC/OC in overloaded filter samples was also developed and evaluated. While emissions (except OC) were found to increase with increasing load, emission factors of PN and OC decreased with increasing load while lowest emission factors for PM2.5 and EC were recorded under medium load. Although limited, the impacts on PM2.5, PN, EC/OC, as well as particle size distribution from biodiesel blends were more noticeable under the lowest and/or the highest engine load conditions and depended strongly on engine type.