The introduction of biofuels is seen as a very important measure
to reduce the emissions of greenhouse gases from the transport
sector. Currently, ethanol is the most widely used renewable fuel
for transportation in the US and with the push to use increasingly
higher levels of renewable fuels, there has been an accompanying
push to further increase the ethanol level in gasoline. In addition
to ethanol, butanol, an alcohol which can be produced from biomass
sources, has recently received more attention as an alternative to
gasoline for use in spark ignition (SI) engines.
For this study, two 2007 model year and one 2012 model year
light-duty vehicles equipped with a three-way catalyst (TWC) were
employed. For the 2007 model year vehicles, emissions and fuel
economy measurements were made for E10 (reference fuel), E15, E20,
and B16 fuels. The latter corresponds to a blend of gasoline and
16% of butanol, which is the equivalent of E10 in terms of oxygen
content. For the 2012 passenger car, in addition to E10, E15, E20,
and B16, emissions and fuel economy tests were also made for
E10/B8. The alcohol mixture of E10/B8 is equivalent of E15 in terms
of oxygen content. Emissions measurements were performed over the
Federal Test Procedure (FTP) and the California Unified Cycle (UC)
test cycles for each vehicle/fuel combination on a chassis
dynamometer. Emissions included nitrogen oxides (NOx),
carbon monoxide (CO), total hydrocarbons (THC), non-methane
hydrocarbons (NMHC), methane (CH₄), and carbon dioxide (CO₂).
Additionally, carbonyl compounds were also quantified in the
exhaust for all vehicle/fuel combinations over the FTP cycle.
Particle size and number were measured with a scanning mobility
particle sizer (SMPS) in tandem with a condensation particle
counter (CPC). The concentration of black carbon was also measured
with a Multi-Angle Absorption Photometer (MAAP).