Emission standards came into being with a single overarching purpose: to check air pollution caused by vehicles around the world. Vehicular emission norms aim to ensure more efficient engines that have less emissions and, in turn, promote healthier living.
All countries have their own emission standards which are almost the same globally. India, too, has its own Bharat Stage Emission Standards based on the EURO emission standards.
What are Bharat Stage Emissions Norms?
In 2000, India introduced Bharat Stage Emission Standards (BSES) to regulate the output of air pollutants from engines. Established by the CPCB (Central pollution Control Board) under the Ministry of Environment & Forests and climate change, these emission standards are based on European standards and get progressively stringent. As per these norms, carmakers should produce engines that pass the emission test laid out by BSES, while oil companies are expected to refine fuel to ensure lower sulphur content. The Indian government in 2016 announced that instead of introducing BSV they would directly start with BSVI emission norms from 2020. This measure was taken to curb the alarming levels of pollution in the country.
What is BS4 (BSIV)?
The predecessor to BSVI, BSIV are Bharat Stage Emission Standards that were finalized in 2014 and enforced for all vehicles in April 2017. These norms were stricter than the previous BSIII norms and led to reduction of sulphur content along with other pollutants such as nitrogen oxide, hydrocarbons and particulate matter in fuel. Under BSIV norms, pollutants from petrol-powered passenger vehicles were restricted to a Carbon Monoxide emission of 1.0 g/km, Hydrocarbons and Nitrogen Oxides discharge of 0.18 g/km, and respirable suspended particulate matter discharge of 0.025.
With the introduction of BSIV, sale of BSIII vehicles was completely banned to ensure overall compliance with changing engine technology and reduce air pollutants.
What is BS6 (BSVI)?
A sea change from previous emission standards, BSVI emission norms came about in April 2020 as the successor to BSIV emission norms. As previously mentioned, the government implemented BSVI emission directly after BSIV, skipping BS V emission norms, citing delayed implementation of the previous norms and alarming pollution levels as the reason for the seemingly abrupt change. BS VI changes apply to engines as well as to fuel quality. How does this impact fuel prices? Fuel now is more refined and less polluting compared to earlier. BS VI fuel has lower levels of sulphur, the main polluting agent in fuels. Removal of sulphur from fuel is a complex process and it costs as much, making fuel costlier to buy.
BS4 vs BS6: Difference Between BS4 vs BS6 and how it is achieved
The most important differences between BS4 and BS6 pollution emission norms are as follows:
- BS6 sets the maximum permissible limit of Nitrogen Oxides (NOx) emissions from a petrol vehicle at 60mg per km. Under BS4 norms, it was 80mg per km.
- Particulate Matter (PM) limit is set at less than 4.5 mg per km for petrol vehicles.
- Moving on to diesel fuel vehicles, limits on NOx emissions is set at 80 mg per km under BS6 standards. BS4 norms had specified the same upper limit at 250 mg per km.
- In diesel vehicles, BS6 norms cap hydrocarbon+NOx emissions at 170 mg per km, down from 300 mg per kg set under BS4 norms.
- Particulate Matter (PM) Limit have been capped at 4.5 mg per km for both diesel and petrol vehicles. This limit was set at 25 mg per km for diesel vehicles under BS4 standards.
Clearly there’s a drop in the permissible level of exhaust gases, but the difference is more pronounced in diesel than in petrol-powered vehicles. BSVI diesel emits as much as 82 percent less particulate matter versus BSIV diesel. Similarly, diesel NOx emissions are also brought lower by a good 68 percent. This significantly narrows the gap between pollution levels caused by diesel and petrol engines. Not a bad move at all.
How are these reductions in pollutants achieved? First, BS6 norms ensure that the sulphur content in fuel gets lowered significantly. Second, it gives carmakers the mandate to build vehicles – and engines – that burn fuel more cleanly and efficiently. This is made possible with improvements in the combustion chamber and the design of the fuel injector. BSVI compliant vehicles also treat their exhausts to reduce emission levels of particulate matter and oxides of Nitrogen. They achieve this by installing a Diesel Particulate Filter (DPF) and a Lean NOx Trap (LNT) or a Selective Catalytic Reduction (SCR) system. The DPF filters the particulate matter and soot that the engine produces while the SCR injects AdBlue, a water-based urea solution, to convert NOx emissions into Nitrogen and Oxygen gases.
Pollution Emission Norms (BS4 Vs. BS6)
At present, the BS6 or Bharat Stage VI emission norms are in place and every vehicle or engine manufactured from April 1 2020 should emit:
Fuel Type | Pollutant Gases | BS6 (BSVI) | BS6 (BSIV) |
Petroleum Distillate Vehicle | Nitrogen Oxide (NOx) Limit | 60 mg | 80 mg |
Particulate Matter (PM) Limit | 4.5 mg/km | - | |
Diesel Fuel Vehicle | Nitrogen Oxide (NOx) Limit | 80 mg | 250 mg |
Particulate Matter (PM) Limit | 4.5 mg/km | 25 mg | |
HC + NOx | 170 mg/km | 300 mg |
Highlighted in grey, in the table you can see that the limit of pollutants, compared to BSIV standards, has been considerably reduced. Some other differences are:
BS IV | BS VI |
Fourth emission iteration | Sixth emission iteration |
Fuel can only be used in BS IV vehicles, and cannot be used in vehicles with BS VI engines. | Fuel can be used in both BS IV and BS VI vehicles. |
Not Applicable | Introduction of Real Time Driving Emissions (RDE) |
Not Mandatory | Mandatory onboard diagnostics |
FAQs about BS4 vs BS4
Q. What is the BS4 full form?
The BS4 full form is Bharat Stage 4, an emissions standard designed to curb vehicle air pollution. It sets the stage for cleaner emissions compared to older standards, with the potential to bring about a significant difference in the Air Quality Index (AQI) upon widespread adoption.
Q. What is a BS6 engine?
A BS6 engine is your eco-friendly powerhouse! These engines meet the Bharat Stage 6 emission standards, emitting significantly lower levels of pollutants. They’re engineered for cleaner performance, giving you a ride that’s gentler on the Earth’s environment.
Q. What is the BS6 full form?
The BS6 full form is Bharat Stage 6, which is the latest and most environment-friendly of all vehicular emission norms. This set of standards is aimed at enhancing air quality by limiting harmful emissions from petrol and diesel vehicles.
Q. What is the difference between BS4 and BS6?
The standout difference between BS4 and BS6 is that BS6 introduces stricter emission limits. For example, the maximum permissible Nitrogen Oxide (NOx) emissions for petrol vehicles drop from 80 mg/km in BS4 to just 60 mg/km in BS6.
Q. How does BS4 vs BS6 impact vehicle performance?
While transitioning from BS4 to BS6 may tweak engine designs and fuel quality, car manufacturers are on a mission to keep performance and mileage just as robust. The focus is on cleaner combustion and better efficiency without sacrificing that exhilarating power.
Q. Why can’t BS6 engines use BS4 fuel?
BS6 engines need a fuel upgrade to meet stricter emission norms, specifically cleaner fuel with lower sulphur content. If you were to use BS4 fuel in a BS6 engine, you’d risk higher emissions, and nobody wants that—especially not the environment!
