Diesel engine emissions: are they no longer tolerable?

Area of Science:

• Environmental Science
• Automotive Engineering
• Chemical Engineering

Background:

• Diesel engines emit complex mixtures of gases and particles, evolving from
• traditional
• to
• new technology
• emissions (EURO 3 and higher).
• Stricter emission standards (EURO 5 onwards) reduced particle emissions but increased nitrogen oxides (NOx), particularly NO2, leading to regulatory issues and the
• Diesel scandal
• due to illegal emissions-cheating software.
• The Worldwide Harmonized Light Vehicles Test Procedure (WLTP) was introduced in 2017 to simulate real-world driving emissions, becoming mandatory for new vehicle certification by September 2018.

Purpose of the Study:

• To analyze the evolution of diesel engine emissions in response to regulatory changes.
• To assess the impact of new testing protocols and CO2 emission targets on diesel and gasoline vehicles.
• To evaluate the relevance of traffic-adjacent air quality measurements for long-term population exposure assessments.

Main Methods:

• Review of historical and current diesel engine emission standards (e.g., EURO 3-6).
• Analysis of the impact of the
• Diesel scandal
• and the introduction of the WLTP testing procedure.
• Examination of fleet-wide CO2 emission regulations and their implications for manufacturers.
• Comparison of energy efficiency and CO2 emissions between diesel and gasoline engines.

Main Results:

• New technology diesel engines meeting EURO 6 standards exhibit significantly reduced emissions, comparable to gasoline engines.
• Despite regulatory advancements, localized air quality near high-traffic roads can still exceed NO2 limits, particularly for older vehicles (EURO 5 and below).
• Diesel engines retain a higher energy efficiency (up to 20%) than gasoline engines, translating to lower CO2 emissions.

Conclusions:

• Current emission regulations and testing procedures (WLTP) have substantially improved air quality from new diesel and gasoline vehicles.
• The future of diesel engines remains viable due to their inherent energy efficiency and lower CO2 emissions compared to gasoline counterparts.
• Restrictions on older diesel vehicles in urban areas based on localized, short-term pollution levels may not accurately reflect long-term population exposure risks and are debatable.