A great drama is going on in Delhi for
the last few days in the name of reducing air pollution. Diesel vehicles more
than 10 years old and petrol vehicles more than 15 years old have been banned
from plying on roads. Trucks are being prevented from entering the city. It’s a
bolt from the blue for the hapless middle class Indian who took a loan to buy a
second hand (used) car or the trucker who had no inkling of what was coming and
was stumped by these orders.
The whole premise on which these orders
have been passed are that diesel vehicles pollute more and the rapid
dieselisation of Delhi personnel vehicles is the cause of pollution. Well, let’s
put things in perspective. Both petrol and diesel vehicles burn distillates of
crude and hence produce similar kinds of pollutants. The five main pollutants
produced by a vehicle operated by an internal combustion engine are:-
- Carbon-di-Oxide.
- Carbon-mono-Oxide
- Nitrogen Oxides
- Hydrocarbons.
- Suspended Particulate Matter.
Of these pollutants, diesel vehicles
produce less Carbon-di-Oxide than petrol cars just by the virtue that they are
more fuel efficient and hence burn less fuel per kilometre. Carbon-di-Oxide is
the main cause for global warming also. Using
a scale of 100 if petrol cars produce 100 Carbon-di-Oxide, diesels
produce only 85.
Carbon-mono-Oxide causes heart diseases
and affects stamina. If inhaled it can lead to death. Diesel engines do not
produce Carbon-mono-Oxide while petrol engines produce it. Using a scale of 100,
if petrol cars with catalytic converter produce Carbon-mono-Oxide equivalent to
42, diesels produce only 2.
Diesel engines produce more Nitrogen
Oxides as compared to petrol. These gases form photochemical smog. If on a
scale of 100, petrol cars with catalytic converter produce Nitrogen Oxide equivalent
to 23, diesels produce only 31.
One of the main hydrocarbons produced by
internal combustion engines is Benzene. It is carcinogenic, causes drowsiness
and cough. Petrol cars produce much more Benzene than diesel. If on a scale of
100, petrol cars with catalytic converter produce Hydrocarbons equivalent to 19,
diesels produce only 3.
As regards SPM, yes diesels produce much
more of these particles as compared to petrol.
Another issue concerns the pollution
when a vehicle is started and driven off. Also called the cold start pollution.
This is a major concern in cities where a huge number of vehicles are started
from cold. In case of petrol cars the time taken for the engine to warm up as
well as the distance required for the catalytic converter to attain
temperatures when they start reducing pollution is double the time and distance
required for a diesel engine to heat up. Hence cars with petrol engines pollute
for longer distances than those with diesel engines. Also it is notable that
cars with catalytic converters are less fuel efficient than those without such
converters and hence produce more Carbon-di-Oxide. Also, these cars are more
polluting till the catalytic converter heats up.
In a normal drive, it takes about 10 km
of driving to get the catalytic converter to temperature. With most commutes in
city being less than 10 kms, the converter never reaches the temperature and
hence these cars pollute more. Diesels have no such issues.
Studies by independent vehicle
researchers TÜV Nord has revealed that Gasoline Direct Injection (GDI) petrol
engines for cars emit more cancer-causing particles than modern diesel engines.
GDI engines make petrol cars more fuel-efficient and reduce emission of
Carbon-di-Oxide. However, findings indicate that these engines release around
1,000 times more harmful particles than traditional petrol engines and 10 times
more than new diesels.
In Delhi, it is known that the main
component of SPM is caused due to dust and construction activities and not due
to diesel vehicles. Roads are not paved well, car parks are made mostly broken mud
flats and there is incessant construction everywhere. Add to it the dust storms
and the air of Delhi is a concoction of SPM. But, is that emissions from diesel
cars? I don’t think so.
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