Impact of Biodiesel Blends on Emissions

A study by the International Council on Clean Transportation (ICCT) found that biodiesel blends impact air quality. Compared to diesel, the ICCT estimates that every 10 percent increase in biodiesel blend increases nitrogen oxides (NOx) by 0.8 percent. Simultaneously, however, it reduces particulate matter (PM) by 4.3 percent, unburned hydrocarbons (HC) by 2 percent, and carbon monoxide (CO) by 2.5 percent. NOx, HC, and CO are byproducts of vehicle engine combustion and contribute to exhaust emissions.

The ICCT's findings are based on a linear regression analysis of 132 studies examining the effect of biodiesel blend levels on vehicle exhaust emissions. This means that with each increase in biodiesel blend, the effect on the increase or decrease in pollutant levels is proportional.

According to the ICCT, this regression model explains approximately 48 percent of the correlation between biodiesel blends and pollutants. The remaining 52 percent encompasses other variables such as feedstock properties, test cycle conditions, and diesel technology advancements.

Further analysis focusing solely on palm oil-based biodiesel revealed a significant increase in emissions. NOx levels could increase by 12 percent at B30, 17 percent at B40, 21 percent at B50, and 41 percent at B100. The reduction in other pollutants, PM, CO, and HC, is largely influenced by modern fuel injection systems and fuel quality.