Study finds ethanol blending appears to reduce significantly genotoxic emissions from gasoline direct injection vehicles
A research team from Empa (Swiss Federal Laboratories for Materials Science and Technology) and the University of Applied Sciences Bern, Laboratory for Exhaust Emission Control, reports that ethanol blending appeared to reduce genotoxic emissions from a flex-fuel Euro-5 gasoline direct injection (GDI) vehicle (a Volvo V60 with a 1.6 L engine) under transient and steady driving conditions.
In a paper published in the ACS journal Environmental Science & Technology, the researchers reported that particle number emissions when operating the vehicle in the hWLTC (hot started worldwide harmonized light-duty vehicle test cycle) with E10 and E85 were lowered by 97% and 96% respectively compared with that of E0. CO emissions dropped by 81% and 87%, while CO2 emissions were reduced by 13 and 17%. Emissions of selected polycyclic aromatic hydrocarbons (PAHs) were lowered by 67–96% with E10 and by 82–96% with E85, and the genotoxic potentials dropped by 72% and 83%, respectively.
Traditional port-fuel injection vehicles are quickly being replaced by the GDI technology in many markets. It is expected that GDI vehicles will represent around 50% of the vehicle fleet in 2020. These vehicles have been introduced promising enhanced engine power and fuel efficiency and hence lower CO2 emissions in comparison with PFI vehicles. However, an important drawback of the GDI technology is the release of nanoparticles of unknown toxicity.
GDI vehicles can release up to 1012 particles/km, exceeding those of current diesel vehicles, which are now equipped with filters, by orders of magnitude. In other words, most GDI vehicles cannot fulfill the Euro-5 particle number limit of 6 × 1011 particles/km applied to diesel vehicles, which is valid for all new type approvals since September 2011 and for all new cars since January 2013.
GDI particles resemble those of diesel vehicles without aftertreatment. They are agglomerates of soot-like nanoparticles formed in the engine under high pressure. In 2012, the WHO classified untreated diesel exhaust as a group 1 carcinogen inducing lung cancer in humans. Due to the striking similarities, concerns on GDI exhausts are on the rise because these exhausts might also be carcinogenic to humans. Therefore, detailed studies on the genotoxic potential of GDI vehicle exhausts are urgently needed to assess these new risks.—Muñoz et al.
In the study, the team compared emissions of a flex-fuel Euro-5 GDI vehicle operated with gasoline (E0) and two ethanol/gasoline blends (E10 and E85) and reported effects on particle, polycyclic aromatic hydrocarbon (PAH), and alkyl- and nitro-PAH emissions and assessed their genotoxic potential.
They applied two driving cycles simulating transient and steady driving. They used the worldwide harmonized light-duty vehicle test cycle (WLTC), which includes urban, extra-urban, highway, and motorway driving. The cycle was investigated under cold- (cWLTC) and hot-start conditions (hWLTC). They also applied a steady-state cycle (SSC) representing mean velocities of the WLTC and idle.
The researchers established a relationship between particle number (PN) and PAH emissions under transient and steady driving under hot- and cold-start conditions. The findings indicated that the release of particles and PAHs, including the genotoxic ones, are well-correlated and that blending with ethanol reduces particle and PAH formation in the engine.
Ethanol blending improves the combustion efficiency and suppresses particle, PAH, and nitro-PAH formation in the engine, thereby lowering the genotoxic potential of GDI vehicle exhausts.
Maria Muñoz, Norbert V. Heeb, Regula Haag, Peter Honegger, Kerstin Zeyer, Joachim Mohn, Pierre Comte, and Jan Czerwinski (2016) “Bioethanol Blending Reduces Nanoparticle, PAH, and Alkyl- and Nitro-PAH Emissions and the Genotoxic Potential of Exhaust from a Gasoline Direct Injection Flex-Fuel Vehicle” Environmental Science & Technology doi: 10.1021/acs.est.6b02606