Compilation of emission factors for biofuels into the GAINS model script
The use of ethanol and biodiesel in the transport sector is increasing in line with the latest legislation, stimulating use of biofuels in efforts to reduce CO2 emissions. At the same time, the aspect of effects from use of biofuel on air quality is a rather contradictory issue, which is currently being studied in many countries. The GAINS model, developed by the International Institute of Applied System Analysis (IIASA) and widely used to provide support to air quality policies, does not provide a possibility to consider emission factors for biofuels used in the transport sector (with exception for CO2).The objective of this study is to link the biofuel share in the transport sector to available emission factors for biofuels, to provide a new emission calculation equation based on this linkage (emissions as a function of biofuel use), to introduce the equation into the GAINS Sweden script, and to compare the results obtained for several scenarios for the Swedish transport sector with different assumed levels of biofuel use. An equation, taking into consideration lower emission factors for NOx and PM from ethanol-fuelled passenger cars, has been derived and successfully compiled into the GAINS Sweden script. A generic equation applicable to other pollutants has also been derived. Calculation results indicate that introducing emission factors for biofuels does not have a significant effect on air pollutant emissions from the transport sector in Sweden. Full replacement of gasoline with ethanol for passenger cars in 2020 reduces emissions of NOx by 1.48 kt and PM by 0.06 kt, according to the baseline scenario (2009). An important prerequisite for obtaining reliable emission results in the GIAINS model is properly quantified emission factors. Further research on emission factors for biofuels is needed since currently used factors are not commonly accepted. The study has been performed within the SCARP research program.