ANY form of economic activity, be it industry or agriculture, transport or more recently the services sector, involves utilization of natural resources in one form or the other. Essential human needs can be met only through goods and services provided by utilization of these resources.

Technological change, population growth and rapid urbanization fuel consumption, create new patterns of human needs and aspirations. Modern consumption patterns and the corresponding production patterns involved in satisfying human needs are leading to an excessive conventional fuel consumption leading to harmful emissions and degradation of natural systems.

Of about 17 million ton of annual petroleum product consumption in Pakistan, the road transport sector alone takes about 47 per cent share in the form of diesel and gasoline, and is considered to be the most dominant source of air pollution in metropolitan areas. Another 33 per cent, mainly fuel oil, is consumed in the power sector. The worldwide review of critical properties of these fuels emanates from a growing concern for the environment and is focussed primarily to bring about qualitative improvement in the fuel properties so as to contain emissions to desirable levels. The two most important questions that have remained focus of discussion in this context include the question of removing lead from gasoline, and the question of removing sulphur from diesel or the fuel oil.

Gasoline, with annual national consumption of 1.2 millions accounts for about 20 per cent of the transport sector needs. One of world’s major uses of lead has been in gasoline since early last century, as it was identified to be a low-cost octane enhancer which would allow higher compression ratio with concomitant improvement in thermal efficiency, fuel economy and antiknock capability. As the environment consciousness took roots, it was found that over 90 per cent of atmospheric lead concentrations in most urban areas were attributable to gasoline lead emissions.

There is sufficient evidence available that human race has suffered adverse health consequences when lead added gasoline is emitted from vehicles. In adults blood, lead is related to blood pressure and to cardiovascular diseases, while in children it may lead even to premature deaths. In addition to negative health consequences, it was further realized that addition of lead to gasoline caused a whole range of problems for automotive designers, including troublesome combustion chamber deposits on pistons, spark plugs and valves, and increased piston ring wear and blow-by rates. Therefore, the question of reducing or removing lead from gasoline came into limelight. The developed world made substantial investments in introducing technological interventions to modify refinery process to raise octane level, or modifying the blending process by using high-octane reformats or alternate octane-enhancing additives to control lead emissions to desirable levels.

In most of the developed world the lead content in gasoline has been eliminated or limited to 0.1 to 0.15 grams per litre. At the same time it has been made sure that the blending process not only yields the desired octane levels, but also other properties associated with the quality of gasoline such as the maximum vapour pressure, benzene and total aromatics stay within certain agreeable limits. The generally agreeable limits for gasoline are Rvp of 9-10 psia; less than 5 volume per cent for benzene, and less than 40 volume per cent in case of aromatics; and sulphur of 1000 particles per million or 0.1 weight per cent.

With the commissioning of PARCO, Pakistan has surplus of gasoline (as naptha, gasoline or blend-stock), and the lead content has been brought down to 0.35 grams per liter with switching over to single grade 87 RON fuel. It still, however, remains higher as compared to clean fuel practices elsewhere. Modifications and additions to existing refineries to meet emerging environmental friendly gasoline specifications offer several options.

Among other options for meeting gasoline pool octane needs and controlling the benzene and aromatic contents to acceptable levels is to effectively address the question of blend-stock (reformate, naphtha, or MTBE) purchases and allocations to existing refineries. This will require commercial arrangements to be worked out either among refineries or through imports of high octane blending components. Further in order to balance the regional demand with domestic supplies, the entire concept of supply zones of the refineries will need to be revisited to optimize logistic costs. The issue of infrastructure improvement for storage and blending of gasoline is another issue relevant enough to merit serious thinking.

Diesel fuel with an annual demand of nearly seven million tons is the second major fuel under consideration. It accounts for eighty per cent of transport sector fuel needs, and for approximately forty per cent of the overall demand for petroleum products in Pakistan. We import about 5.5 million tonnes of high-speed diesel with sulphur content of one weight per cent maximum. The generally acceptable level of diesel sulphur content of one weight per cent maximum. The generally acceptable level of diesel sulphur is 0.5 per cent maximum, though several developed countries have introduced the use of diesel with sulphur as low as 0.005 per cent by weight. The local refineries produce around 1.4 million tons of diesel with a sulphur content ranging between 0.8-0.9 per cent. Diesel emissions contain sulphur in particulate and gaseous form, which are extremely damaging to public health. Diesel particulate emissions have small aerodynamic diameters of less than 10 m/crons and can have a maximum adverse health effect. These particles remain in suspension in the air for hours or days; can travel significant distance from the source; and enter the respiratory tract reaching deep into the lungs.

There exists a clear relationship between sulphur in diesel fuel and particulate emission leading to worldwide trend toward lower levels of sulphur in diesel fuel, as at a minimum, it reduces particulate emissions from diesel vehicles, and in turn, improves health implications. The health and welfare effects of sulphur dioxide in diesel vehicle emissions are probably much greater than that of an equal quantity emitted from a utility stack or industrial boiler, since motor vehicle exhaust is emitted close to ground level near roads, buildings and people.

Other than sulphur, pollutant emissions from diesel are a function of aromatic hydrocarbons, type of additives being used, and volatility of the diesel fuel. Various options to reduce the sulphur content of diesel fuel include using low-sulphur in the crude state or installation of hydrocrackers that would enable production of very low sulphur saturated diesel with high cetane numbers. There are however issues involved with these options. Importing low sulphur crude and modifying the crude mix pose difficulties in the near term as our crude imports from Arab Gulf countries has been on preferential commercial terms and our refineries were accordingly designed to run Arabian light crude oil.

Further in the case of PARCO, the investment by Abu Dhabi is tied to processing at least 40 per cent Abu Dhabi crude oil. The second option of installing distillate hydrotreating is again an extremely capital intensive measure requiring investment of several hundred million dollars and may not fit well with the short term objectives of the country. One possible option to achieve 0.5 per cent sulphur diesel is to import low sulphur diesel and establish blending facilities to support the blending the low sulphur diesel with the locally produced diesel. This option may not be difficult to exercise as the countries in the gulf are shifting to this product in the wake of worldwide demand of low sulphur diesel.

Apart from sulphur content, international trends are for diesel fuel specifications such as to minimise danger of incomplete combustion and the exhaust pollutants, which in turn require good cetane numbers and lower distillation temperatures. This can be achieved by introducing improved fractionation in the refining process.

The third major fuel contributing to pollution in Pakistan is fuel oil, with an annual national consumption in excess of seven million tonnes. The local refineries produce just around two million tons of fuel oil a year while the remaining is imported. Currently almost all the fuel oil being imported or produced by local refineries contains around 3.5 weight per cent sulphur. These levels cause concern especially for areas where population growth has caused residential areas to expand and move closer to the power plants consuming high sulphur fuel oil.

In order to combat the increasing levels of pollution, the government plans to achieve a reduction in sulphur content of fuel oil down to two per cent. Of the several alternatives to achieve this target could be capital intensive measures like installation of residue hydrotreating plants; or installation of flue gas desulfurization plants at the larger power plants close to major conurbation. Again, the option of modifying the crude mix and import of low sulphur crude may not be a workable solution in the near term due to purchase constraints as discussed earlier. I still think the option of importing both low and high sulphur fuel oils, and strategically distributing this imported and locally produced fuel oil according to environmental sensitivity of various regions offers a cost effective solution to the problem in the near to medium term. Switching to environmental friendly natural gas, which is already under consideration of the government offers another wholesome solution to reducing dependence on imports and addressing environmental concerns as well.

The improvement in the quality of gasolines, of middle distillates, and of the heavy fuel oils is synonymous with an increase in the number of processes like isomerization, alkylation, continuous reforming extraction, hydrogenation and prefractionation. As far as furnace oil is concerned, the straight run atmospheric fuel oil sold as furnace oil can be desulfurized by available commercial processes like fluid catalytic cracking, hydrocracking and residual catalytic cracking.

It needs to be understood that there are air pollutants like oxides of the carbon and nitrogen, and scores of chemical compounds, generally resulting from characteristics not directly related to amount of lead in gasoline or amount of sulphur in diesel. These properties relate to incomplete combustion or inappropriate air to fuel mixture inducted into the engines, low fuel quality, poor vehicle maintenance, and a number of other factors that effect vehicle exhaust emissions. It must be understood that we can not clean a dirty engine with a clean fuel. Poorly maintained engines will continue to pollute and this area must be addressed simultaneously.

Also fuel adulteration in various regions of the country has to be stopped effectively, as it also is a cause not only of fuel economy but also of increased level of pollution. Fortunately, progress has been made during the last decade in developing control technologies that can dramatically reduce exhaust pollutants. These technologies involve the physics of combustion, changes in engine design, and exhaust treatment devices.

(The writer is chief of the, National Energy Conservation Centre, ENERCON)