The consumption of fuel by vehicles emits nitrogen oxides (NOx) and non-methane hydrocarbons
(NMHCs) into the atmosphere, which are important ozone precursors. Ozone is formed as a secondary
pollutant via photochemical processes and is not emitted directly into the atmosphere. In this paper, the
ozone increase resulting from the use of biodiesel and diesel fuels was investigated, and the different
ozone formation trends were experimentally evaluated. Known amounts of exhaust gas from a power
generator operated using biodiesel and diesel fuels were added to ambient air. The quality of the ambient
air, such as the initial NMHC and NOx concentrations, and the irradiation intensity have an effect on the
ozone levels. When 30 cm3 of biodiesel fuel exhaust gas (BFEG) or diesel fuel exhausted gas (DFEG) was
added to 18 dm3 of ambient air, the highest ratios of ozone increase from BFEG compared with DFEG in
Japan and Vietnam were 31.2 and 42.8%, respectively, and the maximum ozone increases resulting from
DFEG and BFEG compared with the ambient air in Japan were 17.4 and 26.4 ppb, respectively. The ozone
increase resulting from the use of BFEG was large and significant compared to that from DFEG under all
experimental conditions. The ozone concentration increased as the amount of added exhaust gas
increased. The ozone increase from the Jatropha-BFEG was slightly higher than that from waste cooking
oil-BFEG.