Recently in the NCR region the pollution level has risen to a high level, resulting in the Supreme Court banning registration of new diesel vehicles of more than 2000 cc displacement. Other strong measures like odd and even numbered cars to be run on alternate dates have been enforced by the Delhi government to tackle the problem of pollution.
Recently, the Supreme Court asked whether India could pre-pone the use of Euro-6 fuels to tackle the problem of pollution. A very strong sentiment is emerging against use of diesel vehicles. Diesel vehicles are being considered the main source of pollution.
However, it is not wise to go by feelings, especially in areas where data can be measured and scientific comparisons can be carried out. Long-term policy decisions need to be taken considering all the issues such as what are the items of pollution, fuel availability and the type of pollution produced by vehicles driven by different fuels. We also need to consider the reasons other than vehicular emissions, for high pollution in many of the cities in India.
A comparison of pollution produced by similar vehicles using different fuels has been carried out in the UK and the results are available on the website www.airquality.org. As may be seen from the data there, the air pollution produced by petrol cars without catalytic converters is much higher, except when it comes to particulate matter. The particulate emission from petrol and CNG/LPG fuels is virtually nil. This is where the petrol/CNG/LPG engines score over the diesel vehicles.
In India, most petrol cars are not fitted with the catalytic converters. Therefore the emission of NOx and CO from the petrol cars is much higher compared to diesel vehicles.
The CNG/LPG fuels result in not only nil particulate emission, but also result lower CO, NOx and hydrocarbon emissions. CNG vehicles have a tendency to have higher methane gas in the exhaust, but do not cause smog and other health hazards. In forests, the decay of plant matter results in emission of more methane into the atmosphere anyway.
The Emission of SO2 depends on the sulfur content of the fuel. If sulfur percent is higher, the SO2 percent is proportionately higher. This is where Euro-6 fuels would help, as these have a much lower sulfur content. The best fuels to avoid SO2 pollution are CNG and LPG, which have no sulfur in them and hence emit no SO2. Here it may also be pertinent to note that the wear rate of engines is proportional to sulfur content of the fuel. Thus use of CNG/LPG would enhance the life of the engine and reduce the maintenance costs.
The pollution produced in cold start conditions is much higher for petrol engines than for diesel engines. This point becomes pertinent in cities where, due to start-stop traffic conditions, the engine does not generally get warmed up to optimum operating conditions.
Other Sources of Air pollution
Burning of crop remains to clear field is a major source of air pollution. This produces dense smoke. A study carried out by IIT Kanpur indicated that 50 per cent of SPM present in the atmosphere in the NCR region was due to such burning of crop remains in the adjacent areas. Here again no efforts are being made to address this cause of SPM presence in the air. Similarly, fires in garbage dumps are another source of high pollution in cities. In Mumbai, recently a fire in the garbage dumps at Chembur, caused very high levels of particulate matter in the atmosphere.
High level of dust is another reason for high particulate presence in the air. When vehicles pass over dust, it grinds the dust particles to further fine particles and spreads them in the air.
Choice of Fuel to be Used
The choice of fuel to be used by vehicles would depend upon what is the major pollution issue before us. If the major problem is NOx, diesel or CNG/LPG are better than petrol. However if the major issue is particulate emission, petrol/CNG/LPG are far superior as they emit negligible particulate emission. The choice of fuel, would require large investments in plants and equipment and infrastructure to make these fuels available at the point of usage. Thus choice of fuels cannot be a court decision or on whims and fancies of powerful spokespersons. It needs to be a well-thought out decision and needs to be taken after discussing the issue with all partners involved — the refineries, the director of hydrocarbons and the car makers.
Choices Before India
1. Ban Diesel engines: This is really no choice, as by banning diesel engines, we would be running more vehicles on petrol, which produces more pollution.
2. Promote use of CNG: As the major problem of pollution in Indian cities is particulate matter and NOx, shifting towards CNG as a major fuel for transport and private vehicles would solve both the problems. This would require a dialogue with auto makers and also would require policy decisions to be taken to put up more CNG receiving terminals and pipe lines for its transmission. This would also require fresh investments in production of gas. This would save investment in refineries as the gas can be used directly and no refining is called for.
3. Continue with diesel engines: This would require investment of around `40000 crores for upgrading all refineries to produce Euro-6 diesel. This would also require investment in a new engine management system, which should become mandatory. This system, would sense the amount of CO in the exhaust and if CO rises beyond a pre-determined level, it would not permit further injection of fuel. This would avoid overloading of diesel engine and result in much reduced SPM and CO emission. The driver would then need to shift to lower gear and move forward.
4. As SPM levels are high almost all over India, it is necessary to eliminate loose soil in all urban areas.
5. Similarly burning of bio-mass left in the field after reaping the crop needs to be discouraged.
6. It is also necessary to ensure that better methods of handling the garbage dumps are evolved and implemented.
Forecast for Electric Cars
Continuing research work on electric cars is likely to bear fruit in the coming decade. Advances in battery technology has already made it possible for electric cars to cover almost 180 kms on a single charge. In the next decade I am sure newer batteries would become available reducing the cost of batteries substantially. When this happens, there would be no need to put diesel or petrol engines in cars or trucks. Pollution due to private vehicles would be addressed.
Conclusions
To solve the problem of pollution in our cities, we need do following:
a) Evolve better handling oif garbage.
b) Eliminate loose soil in metros.
d) Encourage users to shift to gas.
The author is an engineer and management professional
Email: k_k_jain@rediffmail.com