Technical Background on India BS VI Fuel Specifications

1 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION, 2016 Technical Background on India BS VI Fuel SpecificationsBackgroundOn February 19, 2016 the Ministry of Road Transport and Highways (MoRTH) issued a draft notification of Bharat Stage (BS) VI emission standards for on-road vehicles in In addition to emission standards for new vehicles, the proposed BS VI regulation contains Specifications for reference and commercial gasoline and diesel fuels. These Specifications define requirements for physical properties and chemical composition of the fuels, and are meant to ensure that commercial fuels are of sufficient quality and compatible with engine and emission control technologies that will be required to meet BS VI emission standards.

2 From an emissions and air quality perspective, the most important parameter defined in the fuel quality Specifications is the maximum sulfur content of gasoline and diesel fuels. In both cases, sulfur content is limited to a maximum of 10 ppm in the proposed BS VI regulation, which matches global best practices. Low sulfur fuels enable the use of advanced aftertreatment control technologies, which greatly reduce emission rates of pollutants that have a significant human health burden, such as particulate matter (PM) and nitrogen oxides (NOX). 1 The Gazette of India , 19th February, 2016 No. 119. Accessed from: proposed BS VI fuel Specifications largely follow European regulations, proposed limits for several commercial gasoline and diesel fuel parameters in India differ from EU values.

3 These parameters include octane number and olefin content for regular grade gasoline; and density, 95% distillation boiling point (T95), and polycyclic aromatic hydrocarbon (PAH) content for diesel. This working paper details these differences in fuel specifica-tions for commercial gasoline and diesel fuels in India and the EU, and assesses potential air pollutant emission impacts of these differences. Gasoline Fuel SpecificationsThe proposed BS VI regulation specifies requirements for two grades of commercial gasoline, regular and premium. Table 1 compares proposed Indian gasoline Specifications with those set in other countries and regions with stringent motor vehicle emission control requirements.

4 For the parameters discussed here, octane number and olefin content, Specifications for premium grade BS VI gasoline match Euro 6 values. For regular grade BS VI gasoline, a lower octane number and higher olefin content is permitted. The potential effects of these differences on air pollutant emissions are discussed in the following sections. WORKING PAPER 2016-9 Table 1. Comparison of fuel Specifications for select gasoline parameters Fuel parameterBS VIEuro 6 EPA RFG average (2005)EPA convetional gasoline average (2005)JapanSouth KoreaWorldwide Fuel Charter (Category 4)Sulfur, ppm, ppm (Tier 2)10 ppm (Tier 3)30 ppm (Tier 2)10 ppm (Tier 3)101010 Research Octane (RON), Octane (MON), Index (AKI), 7/ 8 7/ 9 18 7/ 8 7/ 9 1 NSNSNSO lefins, vol%, max.

5 21 = Not specified; / used to separate Specifications for different gasoline grades; AKI = (RON+MON)/2aMember states are permitted to allow regular grade gasoline with MON of 81 and RON of aromatics 24 max and olefins 16 max or aromatics 21 max and olefins 19 max. Technical Background ON India BS VI FUEL Specifications 2 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION WORKING PAPER 2016-9 OCTANE NUMBERThe octane number of gasoline provides a measure of the fuel s ability to resist auto-ignition, which can cause engine knock and engine damage. The octane number is determined from laboratory testing and, depending on the test method used, expressed as a Research Octane Number (RON) or Motor Octane Number (MON).

6 In some regions, octane rating is expressed using an anti-knock index (AKI), which is equal to the average of the RON and MON of the fuel. In general, octane number is more important to engine efficiency than air pollutant emissions. Higher-octane gasoline allows for higher compression ratios and engines can be designed and optimized for thermal efficiency. However, researchers have shown that fuel RON and changes in fuel composition associated with RON do not have a significant effect on regulated pollutant emissions from gasoline This is in part due to the fact that engines are designed and calibrated to operate on fuel of a specified octane rating.

7 As shown in Table 1, RON and MON Specifications for regular grade BS VI gasoline (91 and 81) are lower than for Euro 6 gasoline (95 and 85). While these differences may have an impact on the fuel economy of the Indian fleet, they are not expected to impact air pollutant emissions. As evidenced by the United States, it is possible to have low emitting vehicles fueled by gasoline with octane ratings similar to those proposed for Indian BS VI regular grade gasoline. The AKI calculated from RON and MON Specifications for regular grade BS VI gasoline is 86. This is very close to the AKI specified for regular grade gasoline in the United States, 87.

8 Furthermore, both Japan and South Korea, where emission standards equivalent to Euro 6 have been adopted, have RON Specifications for regular grade gasoline at or below the level set in the proposed BS VI standards. This means that, with respect to octane number, India will have similar requirements to other countries that have adopted world-class emission India , ethanol is blended with gasoline blendstocks to produce a final commercial product. The current ethanol content of commercial gasoline in India is about 5% by volume. In coming years, ethanol content is expected to increase to nearly 10% by volume. Because ethanol has a higher octane number than gasoline, it serves to enhance octane rating when mixed with gasoline.

9 Anderson et al. investigated the relationship between ethanol content and octane number and developed a linear blending model to estimate the octane number of gasoline-ethanol 2 Esterhuyse, and Yates, A Study to Assess the Effect of Octane on Vehicle Emissions, 2002, SAE International, Using this model, blending 91 RON gasoline with 5% and 10% ethanol by volume would result in a blend with final RON of approximately 94 and 96 respec-tively. Similarly, blending 81 MON gasoline with 5% and 10% ethanol is estimated to produce a blend with a MON rating of 83 and 85 respectively. OLEFIN CONTENTO lefins are a class of hydrocarbon compounds charac-terized by the presence of at least one carbon-carbon double bond.

10 The presence of this double bond makes olefins more reactive than other gasoline components such as paraffinic or aromatic compounds. This reactivity has several implications for combustion dynamics and air pollutant emissions. Generally, increased olefin content improves combustion efficiency, which may lower hydro-carbon (HC) emissions and increase NOX emissions. Increased olefin content may also result in increased emissions of the air toxic 1,3-butadiene, which is a product of the incomplete combustion of olefin Because of their reactivity, olefins also tend to have higher ozone formation potentials than other hydrocar-bon components in gasoline fuels.