NREL data sparks NOx controversy

It's generally accepted that biodiesel blends, while reducing almost all harmful diesel vehicle emissions, lead to slightly higher levels of NOx.

In the presence of air and sunlight, ambient NOx, along with hydrocarbons (HC) or volatile organic compound (VOC), undergo photochemical reactions to form ground-level ozone (O3).

Findings show consistently higher NO and NO2 concentrations on weekdays compared to weekends.

Study observed significant increases in O3 levels on weekends to that of weekdays.

This study drives home the idea that NOx may not be a governing a factor in controlling O3 formation as was once thought.

Weekend Ozone Effect

A breakthrough study - the Weekend Ozone Effect - has government scientists, policy enforcers and biofuels advocates abuzz over data indicating that less NOx is precisely what's not needed to control the formation of ground-level ozone in urban areas.

A collaborative analysis was conducted by the National Renewable Energy Laboratory (NREL), the Coordinating Research Council (CRC) and the California Air Resource Board (CARB); and funded by the U.S. Department of Energy (DOE).

Essentially, the study compares weekday and weekend traffic patterns and ambient conditions in the same areas. Less traffic on the weekends produces less NOx emissions (NO and NO2), one-third of all of which comes from diesel emissions.

After five years of data collected from southern California study points to a need for a new approach to a not-so-new problem.