A new study shows that biodiesel used in buses cuts down on the amount of air pollution compared to buses using more conventional diesel. This news release from the Mineta National Transit Research Consortium (MNTRC), a coalition of nine university transportation centers led by the Mineta Transportation Institute at San Jose State University, showed that using biodiesel could effectively reduce the mass of particulate matter released in both hot and cold idle modes.
[Principal co-investigators were Dr. Ashok Kumar] said, “Physical properties of biodiesel blends are very important during engine combustion. Higher viscosity causes reduced fuel leakage during injection, which drives an advance in injection timing and an increase of mass injection rate. Density of the fuels affects the start of injection, injection pressure, fuel spray characteristics, etc. When the fuel temperature changes and enters an engine with different temperatures (hot or cold), fuel acts differently and the emissions are different.”
In sum, it is recommended that governments consider using blends of biodiesel in urban and commercial vehicles to enhance the quality of air and to promote healthy living.
Among the report’s findings:
Combustion temperature and pressure of biodiesel blends are linearly correlated with the portion of oxygen in biodiesel fuels. This information can be used to make proper blends of biodiesel with regular diesel.
The high oxygen content of biodiesel improves the oxidation of soot precursors and limits soot mass growth, resulting in less particulate matter formation.
The results also confirmed that better combustion, with less emission of elements, occurred in hot idle mode (i.e., when engines were fully warmed) rather than in cold idle mode (i.e., at morning start-up).
The results indicated that the use of biodiesel could effectively reduce elemental carbon, which is considered more hazardous than organic carbon.
Source apportionments of detected elements are done by using laboratory experiments as well as field experiments.
The neural network method along with the kinetic models is implemented to help us better understand the particulate matter formation mechanisms and come up with more efficient and effective operating conditions to reduce PM emissions.
Higher flash point of biodiesel, suggests that it is safer than other fuels, and storage process is easier.
You can read the full report here.