Controlling the “Silent Threat” in BS7 – Evaporative and Refueling Emissions
Throughout India, petrol-fueled internal combustion engine (ICE) vehicles emit non-exhaust evaporative and refueling volatile organic compound (VOC) emissions at levels which significantly exceed tailpipe exhaust emission.
During periods of heat waves, when air quality is often most unhealthy and severe, petrol-fueled ICE vehicles in India can have emissions of evaporative nonmethane hydrocarbons (NMHC) that are up to 30 grams per vehicle per day, which is 15x higher than the current BS6 evaporative emission certification standard (2.0 g/day) and 13x higher than the BS6 exhaust NMHC emission standard (68 mg/km).
In Delhi alone, this amounts to 113 tons per day of unburned fuel being emitted into the atmosphere. This will continue to increase as India moves to ethanol-containing fuels with higher vapor pressure. The unburned fuel in the atmosphere is a primary precursor for the formation of ozone (O3) and secondary organic aerosol (PM2.5) and regional haze.
As India evaluates options for BS7, it is important to consider the unique environmental conditions in India that warrant a different approach than simply following Euro 7, which is the weakest evaporative emission standard when comparing against the standards implemented in the other major automotive producing countries that desire to improve air quality (US, Canada, Brazil, China).
Euro 7 applied in India would not be sufficient to mitigate the high in-use evaporative emissions that occur due to the higher ambient temperatures in India. At a minimum, India should implement evaporative and refueling emission standards and limits equivalent to Brazil. These standards would reduce evaporative and refueling emissions by more than 92% during all possible in-use conditions and retain the valuable fuel vapor on the vehicle to be burned in the engine as fuel, saving consumers on fuel costs and reducing their exposure to air toxics found in petrol, such as benzene.
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