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ENVIRONMENT: CLEAN DELHI
THE SEARCH FOR CLEAN FUEL
The Gas War Hots Up
Delhi could well
have the world's cleanest transport system when the entire 10,000-strong
CNG-driven fleet is pressed into operation. It will be a world first too.
CNG has been used as a fuel for decades, but no city has an entire CNG-driven
public transportation system. To be sure, it's a drastic measure. But
with Delhi's high pollution levels, drastic steps are needed to prevent
children dying from breathing foul air, says Anil Agarwal, director, Centre
for Science and Environment (CSE). Few long-suffering Delhi residents
would disagree. But why CNG? "It is the cleanest fuel that removes
pollution dramatically and quickly, and its use is possible with both
old and new vehicles," says Agarwal.
A report from the other major green NGO, Tata
Energy Research Institute (TERI), disagrees. It insists that a cleaner
version of diesel, called ultra-low sulphur diesel (ULSD), would have
been equally effective. And the fuel would have worked on diesel engines,
preventing the expense of large-scale engine conversions. "CNG buses
account for only an insignificant share of city fleets worldwide,"
notes Ranjan Bose, senior fellow at TERI and author of the report. "Alternatives
should have been discussed and been in place by now."
Chemically, both diesel and CNG have the same
carbon backbone. In diesel, the backbones hold hands to form a long unwieldy
chain that easily breaks apart at a relatively lower temperature. It provides
a great deal of energy, but the price is a host of un- pleasant leftovers.
The unburnt fragmented solid bits, called particulate matter, is expelled
as sooty black diesel exhaust. Sulphur, a common contaminant, makes particulates
worse. It also leads to another deadly byproduct-sulphur dioxide. CNG,
on the other hand, is a stable compact little molecule. It needs the assistance
of a spark to combust. Being a light gas it is generally sulphur-free
and burns well. The poisonous byproduct carbon monoxide is converted to
the slightly more acceptable carbon dioxide. Definitely, CNG is the cleaner
option.
ULSD is diesel that has a sulphur content of
just 0.005 per cent. The introduction of ULSD in the UK delivered a reduction
of 8 per cent in particulate emissions in urban areas. Particulate traps,
as the name implies, snares the offending particles and converts them
to harmless substances. These only work effectively with low sulphur fuel
like ULSD. These devices can then deliver particulate reductions of 90
per cent compared to a similar vehicle without a trap. Says Mark Gaynor
of the UK's Department of Environment and Transport: "ULSD is now
the only form of diesel available for most transport applications in the
UK. But we are also encouraging the wider use of gas vehicles."
In most of Europe it's a similar story. A British
study, cited by TERI, concluded that a combination of ULSD and particulate
trap delivered similar emissions benefits as CNG. The gas-based vehicles
would have been significantly quieter than diesels, though. Unsurprisingly,
in this green battle CSE has cited an Australian study showing CNG as
far cleaner in terms of particulate matter. The CSE stresses that it's
not just about particulate matter. Diesel emits known carcinogens like
benzene which CNG does not. A New York Transit study on the other hand
revealed that CNG does emit ultrafine particulate matter that could be
far worse for the lungs.
As the controversy rages, all the studies boil
down to the nitty gritty-factors other than fuel affecting vehicular pollution.
"The best of fuels will pollute if the engine is an old one,"
says A.K. Bhatnagar, director (R&D), Indian Oil Corporation. "We
must also look into road conditions, traffic, maintenance and engines."
There are logistical problems too. The shift
to CNG has clearly been expensive (see box). Then there are infrastructure
problems. Delhi is supplied by a gas pipeline running from Haldia to Jagdishpur,
but this may not be an option for other cities. There are not enough CNG
fuelling stations, and refuelling takes longer. Would ULSD have been a
better option? The particulate trap, necessary to make it as clean as
CNG, would cost around Rs 2 lakh and would have to be imported. ULSD also
functions best with a more advanced Euro 3 engine. Cleaning up sulphur
in diesel further would cost oil companies Rs 10,000 crore. In Europe,
companies receive financial incentives for green fuels. Indian companies
have no such benefits to drive them down the green route.
"There should have been trials and evaluation
in our conditions before a decision was made," says Rajendra Pachauri,
director, TERI. "We must find solutions which are applicable to other
cities in the country too." The solution need not be black or white.
A CNG/ULSD combination fleet, as followed around the world, may have been
a more practical alternative. The conversion process could have been staggered
so that commuters were not inconvenienced. The gain from CNG buses could
be lost by the many cars and two-wheelers that continue to clog Delhi's
roads. Only a far-sighted comprehensive transport policy can be truly
effective in cleaning Delhi's air. There are no short cuts.
-Supriya Bezbaruah
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