FUEL quality and vehicle emissions are closely linked and affect the level of air pollution. The widespread consumption of low quality fuel combined with a dramatic expansion in the number of vehicles on the roads, has led to significant air pollution problem especially in large cities.

The air in Karachi in the past decade had become one of the most polluted in the world. Concentration of total suspended particulates (TSP) in Karachi is three to four times higher than the level identified as safe by WHO. concentration of oxides of sulfur (SOx) and oxides of nitrogen (NOx) are also significantly above safe levels. It has been estimated that motor vehicular emissions contribute more than over 60 per cent of pollutant in Karachi. Motor vehicle emissions in Lahore account for approximately 90 per cent of the total annual emissions of hydrocarbons, aldehydes, and carbon monoxide, and emissions of sulphur dioxide and nitrogen oxides.

Exposure to high level of air pollution poses a major threat to human health. According to ministry of environment in 2001 the cost of air pollution was Rs25 billion in terms of treatment of resultant diseases and 6.4 million people were hospitalised for pollution-related illnesses. Motor vehicles are the leading source of air pollution that adversely affects the economy and population.

Problem of air pollution is more acute in highly congested business centres in metropolitan cities where movement of air is minimal. The problem has been compounded by continuous increase in number of vehicles on the road and presence of old model vehicles which have completed their lifetime. Old model automobiles are energy inefficient and emit more hazardous gases than the standards recently adopted by the auto-industry. In our cities old vehicles stay on the roads because of the absence of emission regulations, lack of enforcement of motor vehicle fitness regulations, and the owner’s lack of capital to purchase replacements.

The number of vehicles has increased from 2,951600 in 1992 to 6,048300 in 2005. The biggest increase in the automobile sector is seen in two-stroke vehicles and diesel-powered goods lorries which are among the most polluting.

Because transport is one of the major contributors to urban air pollution, reducing vehicle emissions is an important part of a strategy for managing urban air quality. The government is promoting the use of compressed natural gas (CNG) to reduce pollution caused by vehicles and to improve the air quality. Medium Term Development Framework (MTDF) has set target to increase CNG use in transport sector from 21000 million cubic feet per annum in 2004 to 33900 million cubic feet per annum in 2010.

Rising petrol prices has increased the demand of CNG cars and the country has witnessed massive conversion of gasoline (petrol) cars to CNG, especially in the last two to three years. By the end of April 2006, about one million vehicles have been converted on CNG. As on May 2006 some 930 CNG stations are operational in the country while 200 are under construction. With these developments, Pakistan has become the leading country in Asia and the third largest user of CNG in the world, after Argentina and Brazil.

CNG is compressed form of an ordinary natural gas that is widely used as fuel in homes, industries and factories. At atmospheric pressure, it is too bulky to be stored or be of much value to car and truck/bus engines. When natural gas is compressed at high pressure the energy stored in the vehicle increases giving the vehicle a reasonable mileage between refills. Numerous CNG stations have been opened in big cities to facilitate refuelling.

CNG is less expensive than petrol, has lower regulated pollutant and toxics emissions, produces less greenhouse gas (GHG) emissions, and is available in major cities of the country. Additional natural gas transportation and distribution infrastructure required for large-scale use of natural gas for transportation is well developed.

High ignition temperature and resistance to self ignition give CNG excellent anti-knock properties. Octane of CNG is 130, which is considerably higher than 93 octane for petrol; Thus, engines exclusively designed for natural gas can use high compression ratios and achieve higher efficiencies than gasoline engines. However dedicated CNG vehicle can be stranded on the way for want of gas due to limited number of CNG filling stations. Also, the motorist witness long queues at CNG filling stations due to inadequate number of filling stations and lengthy refuelling time. At present, almost all CNG vehicles in our country are of duel fuel type and also operate with petrol.

The price of compressed natural gas (CNG) is higher than the international market. Still mileage wise, the cost of fuel of CNG vehicle is half that of petrol vehicle due to heavy taxation on petrol.

However according to Petroleum Policy 1997; the use of CNG in vehicles is being encouraged to reduce pressure on petroleum imports, to curb pollution and to improve the environment. The existing price differential between CNG tariff and motor gasoline will be maintained as an incentive for CNG use.

Any move by the government to increase in the price of CNG to bring down the existing price differential between CNG and petrol tariff may restrict the demand for CNG vehicle. When financial incentive is withdrawn, motorist may not find environmental benefits as inspiration to invest additional 20-30 thousand on CNG kit and make long queues at CNG filling stations. This may risk the interest of invertors in CNG sector. According to Economic Survey 2005-06 an investment of Rs20 billion had been made in the CNG sector and Rs2 billion are in pipeline. The CNG industry has also created 20,000 jobs.

Pakistan currently is producing about 64,000 barrels per day of its own oil, while in 2005 it consumed an estimated 351,400 barrels per day. Local refineries process Light Arab Crude, of which 45 furnace oil, 15 naphtha, 22 diesel and 18 per cent kerosene are refined. By contrast, Pakistan has an estimated 26.83 trillion cubic feet (Tcf) of proven natural gas reserves, and is essentially self-sufficient with natural gas.

Historically the consumption of diesel in the transport sector has far exceeded that of gasoline. Diesel vehicles of the technology used emit much more pollutant than petrol vehicles. According to the World Health Organization, diesel exhaust is probably carcinogenic. Diesel exhaust has a high fraction of polycyclic aromatic hydrocarbons (PAHs) and suspended particulate matter (SPM) that cause cell mutations which may ultimately lead to cancer. High quality diesel with low sulfer emits very minute particles, which can even penetrate deep into the lungs.

Pakistan has imported about 4.2 million tonnes of diesel oil at a cost of around $1.7 billion during 2004-05. According to ministry of Petroleum and Natural Resources 1.3 million tones surplus naphtha/motor gasoline was available for exports during 2005-06.

These statistics show there is a strong need for replacing diesel oil to the extent it is possible with CNG to reduce the level of air pollution and to reduce pressure on petroleum imports.

Diesel vehicles are more expensive to purchase and operate than their gasoline equivalent. In areas where CNG stations are not in operation, conversion of light-duty petrol engines to diesel is a common practice as the price of diesel is about 40 per cent less than that of gasoline.

While the existing heavy-duty diesel vehicles such as large trucks and buses will continue to run on diesel irrespective of the inter-fuel price differences because of several engineering and management problems related to conversion of bus fleets, light-duty vehicles running on diesel might eventually switch to CNG when more CNG filling stations become operational and prices of diesel and CNG are adjusted to favour CNG mileage economy. Diesel is used in freight transport, so a marked rise in the price of diesel could result in inflation.