Leading passenger vehicle markets such as the European Union are opting for other fuels.

The story so far: On April 25, Maruti Suzuki, India’s top carmaker, announced that it would phase out production of diesel models from April 1, 2020, when stricter Bharat Stage VI emission standards come into force. What does this mean for the auto industry?

Why did Maruti take this decision?

Explaining its rationale, the leading passenger vehicle manufacturer said the enhanced emission standards would make diesel engines costlier by up to ₹1.5 lakh, and the acquisition cost of diesel vehicles for consumers would be markedly higher than petrol equivalents. Given the market dynamics, it would not make business sense for the company to invest in developing new diesel engines to meet the BS VI norms. Compressed Natural Gas could be a replacement for both fuels, according to Maruti.

Diesel cars account for about 23% of Maruti’s domestic sales and it sold a total of 4.63 lakh diesel-powered vehicles during 2018-19.

On the consumer side, diesel vehicles are not particularly attractive today. The traditional advantage of lower operating costs due to a wide gap between expensive petrol and lower cost diesel has narrowed significantly. On Saturday, the price of diesel in a city like Chennai was ₹70.48 per litre compared to ₹75.92 per litre for petrol.

Environmentally, diesel is a heavy polluter and is losing ground in leading passenger vehicle markets such as the European Union. The rigging of emissions data by Volkswagen to show lower levels of nitrogen oxides accelerated the move away from diesel. Even in Germany, which is a leading maker of diesel cars, cities want to ban them.

Why is the move significant?

India has a growing vehicle-to-population ratio, although it is still lower than several other big countries. While Maruti’s is a business decision, policy decisions on emission norms will steer the industry, and are therefore critical to improving air quality.

Ambient air quality has deteriorated so badly that 15 Indian cities led by Gurugram are among the 20 most polluted cities globally as per the IQAir AirVisual ‘World Air Quality Report’ for 2018, based on fine particulate matter (PM2.5) that penetrates the lungs and bloodstream. Transport emissions, particularly from diesel, are a major contributor.

As of 2017, India’s installed capacity for vehicle production stood at 7 million four-wheelers and 27.56 million two and three-wheelers. Commercial three-wheelers, such as large autorickshaws, sold in the past include heavily polluting diesel models that continue to operate even in densely populated cities.

During 2017-18 the auto industry produced over four million passenger vehicles and just under 900,000 commercial vehicles, according to the Society of Indian Automobile Manufacturers.

After the decontrol of diesel pricing about five years ago, the share of diesel models in car sales has dropped from nearly 43% in 2012-13 to 23% at the end of 2018.

What is diesel’s pollution profile?

The Auto Fuel Vision and Policy 2025 published by the erstwhile Planning Commission, which laid out the road map for a transition to less polluting fuels, pointed out that sulphur in diesel is a contributor to particulate matter both in the vehicular exhaust and in the atmosphere. Sulphur is found in petrol too, but for comparison, it was 2,000 parts per million (ppm) in petrol before introduction of standards in 2000, but in diesel it was 10,000 parts per million (ppm) in 1996. Sulphur content was reduced with each phase of upgradation of emission standards to touch 50 ppm under BS IV. In BS VI, which is already dispensed in Delhi, it is 10 ppm.

Sulphur plays a key role since higher concentrations have an impact on technologies for control of other pollutants in the emissions, such as carbon monoxide, particulates, oxides of nitrogen and hydrocarbons.

The importance of cleaner diesel was studied in Karnataka, and data show that adoption of Bharat IV diesel in 2015 had an impact on the sulphur dioxide (SO2) concentrations. The sulphur content of diesel changed from 350 ppm to 50 ppm. There was a 25% drop in nitrogen dioxide (NO2) concentrations too, which could also be linked to change in the fuel quality. But such gains were neutralised by traffic growth. The rise in larger PM10 concentrations by 50%, was linked to growing numbers of vehicles and dust resuspension, besides construction activity.

Even with cleaner fuel, increase in vehicle numbers, especially those running on diesel cut into the gains. It was witnessed in Delhi, where, in spite of a shift of buses and autorickshaws to CNG during 1998-2002, the air quality gains were soon lost to explosive motorisation.

Bengaluru also had a similar experience, as a study by the Air Pollution Knowledge Assessment City Program by Urbanemissions.info showed. The city has steadily motorised, and number of vehicles registered per 1,000 population increased from 150 in 1990 to 300 in 2001 and 600 in 2016.

Within the transport sector, more than 70% of PM2.5 emissions were found to originate from a small fraction of diesel-powered vehicles. Also an estimated 200 million litres of diesel are used by diesel generator sets in the city annually.

Data for Delhi from 2011 led researchers to conclude that on-road commuters are exposed to 1.5 times the average ambient concentrations. Automotive emissions add to the pollution burden imposed by manufacturing and construction activity, power plants, biomass burning for cooking and heating, and incineration of farm residues and garbage.

How can eliminating diesel improve health?

Air pollution is a leading contributor to non-communicable diseases and accounts for a large number of premature deaths. The World Health Organisation describes diesel exhaust as an occupational cancer-causing agent.

In India, the Global Burden of Disease Study 2017 attributed 8% of the disease burden, and 11% of premature deaths in people below 70 years of age to air pollution.

An assessment by researchers published by The Lancet Planetary Health in December 2018 said most Indian States, particularly those in north India, and 77% of the country’s population were exposed to an annual population-weighted mean [fine particulate matter], PM2·5, greater than the 40 microgrammes per cubic metre of air limit recommended by the National Ambient Air Quality Standards.

Even with a reduction in the sulphur content in BS VI fuels, the health effects of lower emissions would be lost due to a growing number of vehicles. The best scenario to reduce PM2.5 exposure in India is, therefore, not just shifting to BS VI fuels but bringing about a reduction in use of private vehicles through augmented public transport and promoting alternative fuels including the use of electric vehicles.

In his book, The Invisible Killer, air pollution scientist Gary Fuller says diesel cars were promoted by a variety of actors, such as oil companies, governments, and vehicle manufacturers in the 1990s in order to create a market for the middle fractions of crude oil. Real-world emissions in new cars have not always aligned with expected type-approval tests. While test cycle nitrogen oxide emissions decreased by 80% since 1992, the real driving emissions from diesel cars increased about 20%, says Prof. Fuller in a recent paper.

In Europe, trucks and buses were already running on diesel, and industries and governments promoted its use in cars, giving petrol a lesser profile. Car makers produced newer diesel engines and promoted them citing lower carbon dioxide (CO2) emissions compared to petrol equivalents.

India has slowly moved towards stricter regulation through mass emission norms for vehicles. The first standards came into force in 1991 for petrol vehicles, and a year later, for diesel vehicles. Based on Supreme Court orders of 1999, the Central government notified the Bharat Stage II norms for the National Capital Region and Bharat Stage I for the rest of India, from 2000. After transitioning over the years to BS III and BS IV, BS VI (the equivalent of Euro VI) standard will cover vehicles manufactured on or after April 1, 2020. (BS V has been skipped altogether.) Its 10 ppm sulphur standard will be less polluting, since the current level is 50 ppm.