Search for cleaner fuels: CNG or LPG?

THE SEARCH for a cleaner motor vehicle fuel appears to have started in right earnest in the country, throwing up a multitude of problems. The bursting of a fake CNG cylinder, while being filled at a petrol pump in Ghatkopar, Mumbai, and the troubling situation in New Delhi, with road transport operators failing to comply with the Supreme Court order on conversion to CNG, clearly underline the fact that ad hoc solutions will not solve automotive emission and pollution problems. The developed countries, particularly Germany, France and the US, (California), have come up with stringent pollution control norms on vehicle emission.

The participation of vehicle manufacturers and fuel suppliers is essential to make any plan a success in the battle against pollution. There cannot be any single solution/fuel that will give the desired results. This has been conclusively proved in the developed countries. In India, we do not seem to be aware of the developments in cleaner fuels and engine technology, and even if we are, the specifications are not enforced. This has been amply demonstrated in the haste in which CNG conversion has been stipulated in New Delhi, without first putting in place the various requirements to meet such conversion targets.

Both Compressed Natural Gas (CNG) and Liquefied Petroleum Gas (LPG) are known to be cleaner fuels, with specific hydrocarbon contents, pressure ratings and handling requirements.

As the name itself suggests, CNG consists mostly of methane, which is compressed to 80 atmospheres -- a huge pressure rating. CNG is the ideal fuel for trucks, buses and light commercial vehicles (LCVs) that operate within city limits at low speeds, as an alternative to high-speed diesel. These vehicles are unable to run in the cities at their optimum speed and, hence, the incomplete combustion releases huge amounts of carbon-monoxide into the air, apart from other harmful emissions. However, the high-pressure cylinders mounted on heavy vehicles can be protected from accidents and can be refuelled at exclusive CNG filling stations. The crew of these vehicles can also be educated to handle CNG as a fuel.

Vehicle manufacturers, on the other hand, must start fitting CNG engines in their products. The conversion kits for diesel engines will also have to be fitted. It must be clearly understood that CNG cannot be supplied by the oil companies on a subsidised basis for any further prolonged period.

As regards two/three-wheelers and cars, including taxis, it is dangerous to operate these vehicles on CNG. Care should be taken to ensure proper methods of certification of the high-pressure cylinders, and mounting of the same in the vehicles should satisfy all safety standards. Taxi-drivers must also be trained to handle the cylinders, to prevent safety hazards or any untoward accident.

LPG operates at a much lower pressure (8 kg/cm2), is a clean fuel and can easily be imported and used to operate two/three and four-wheelers. The country has limited resources of natural gas, and huge investments are required for bringing it into the country, either in the form of LNG or through pipelines. Hence, the prioritisation of natural gas utilisation must be in the following order:

*Power generation.

*Petrochemicals.

*Fertilisers.

It would, indeed, be foolish to squander the scarce gas as transport fuel, primarily. Dispensing facilities/outlets for delivering LPG cylinders to cars and taxis, however, can be set up in small areas of the cities. Wherever space is available in existing petrol pumps, replacement of the LPG cylinders can be done at the outlet itself, as in the case of residential units. But there must be proper support and metallic binding to the LPG cylinders to ensure that they are firmly fixed in the boot of the four-wheelers.

It will be dangerous to refill LPG cylinders from dispensing units at outlets, as any leakage can cause immediate explosions and accidents. What we need are LPG cylinders of a commercial size that can be firmly fitted in two/three-wheelers and four-wheelers, but can be detached when empty, so that the new cylinder can be replaced easily.

The Explosives Department, Nagpur, can come up with a proper structure enabling the mounting of LPG cylinders, and replacing with filled cylinders at retailing points. The Government, through an Act in Parliament, has already approved the use of LPG in vehicles and only the modalities of cylinder design by the Explosives Department and the approval of the Transport Ministry are to be obtained. The trend in Europe is towards LPG rather than CNG. Also, factory-fitted LPG kits by the manufacturers themselves will be of immense help.

It is necessary to phase out two/three-wheelers using two-stroke engines, particularly in the cities, where 60 per cent of the carbon monoxide emissions is through two-stroke engines. There is an urgent need to replace the vehicles with at least four-stroke engines and, if possible, promote the wider use of LPG as a fuel. To understand more about vehicular pollution, look at the report prepared for the Ministry of Environment and Forest, Government of India under the Project No. Q-16014/13/90-CPA and the conclusions and recommendations of the report.

P. Ramakrishnan