The use of CNG in light-duty vehicles is well known and
widespread in Brazil, mainly in the state of Rio de Janeiro. In
theory, the application of this technology could provide greater
energy efficiency and lower emissions of pollutants. However, it is
known that the majority of CNG kits installed do not meet the
environmental requirements established by the Brazilian
legislation.
This work quantifies the average emissions from light-duty
vehicles converted to CNG use in the Metropolitan Area of Rio de
Janeiro, where 47% of the Brazilian CNG fleet runs. For this
purpose, initially a field survey of gas stations was performed in
this Region, in order to define the representativeness of CNG kits
in terms of technology generation and brand, as well as
manufacturer, model, displacement, original fuel and manufacture
year of vehicles in which such kits were installed.
Based on the results of this survey, six vehicles adapted with
CNG kits were selected for FTP-75 tests of emissions and fuel
economy in the Vehicle Testing Laboratory of PETROBRAS Research
Center (CENPES). Then it was calculated a weighted average of the
emission of THC, NNHC, CH₄, CO, NOx, aldehydes and CO₂ in vehicles
with CNG kits in the Metropolitan Area of Rio de Janeiro.