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Lynford Johnson, owner of Johnson's Gas Station, pumps gas at the popular outlet in Kingston.

Mario James, Gleaner Writer

WHY IS diesel fuel more expensive than gasolene? This has been a hot topic for many months now. To understand why, Automotives turned to Telroy Morgan, manager of refinery operation at Petrojam for an answer.

He explains: "To understand why, one has to comprehend the process. First, crude oil is not a compound, it is an amalgam of many different substances. Our first task is to separate these substances, and we do this in what is called a fractionating tower. Fractionating is just a fancy word for distilling.

"As the tower applies heat (indirectly) to the crude, these fractions (substances) turn to vapour and boil off. The tower is constructed so as to collect the different fractions at different levels in the tower.

"It can be inferred that the fractions have different densities, and therefore collect at different heights in the tower."

Think of gasolene and water 'mixed' in the same container. After a while, two distinct strata are seen.

"At the very top of the tower, we have a mix of liquid petroleum gas (LPG) and light fuel gases, such as ethane, methane, etc. At the very bottom of the tower, fuel oil is extracted, to be burnt by the JPS, ships and other industrial applications. In between, there is diesel, kerosene and gasolene, diesel being the lowest fraction.

"Sulphur, an element that is always present in crude oil, has to be removed after the fractioning process. Gasolene, as it comes out of the tower, has an octane number of less than 75, which is unsuitable for consumption in today's engines. It has to be reformed, a process which rearranges the gasolene molecules.

"This process is expensive, as it involves the use of a catalyst that contains platinum."

Grades of crude oil

All this points to gas being more expensive to produce than diesel, right? But wait, there's more.

"Two things now define the fuel price structure post-refinery," Morgan intoned. "One is the age of the plant (Jamaica's refinery was built in 1966). The refinery has to be fed a certain diet of crude for it to operate efficiently. We buy two grades of crude oil and blend them to get the American Petroleum Industry (API) index we need, roughly 27 or 28 API. When we distil, or fractionate, this blend, we get approximately 50 per cent (fuel oil), 15 per cent diesel, 13 per cent kerosene, 17 per cent gasolene (a portion of which is blended with kerosene to produce aviation fuel) and five per cent LPG.

"Now, the refined fuel oil is sold for less than the crude oil price, and the energy market is moving away from it because it is not as green as the higher margin fuels. So, it is getting harder to sell. We need a refinery that will be more efficient, with lighter crude oil blends, as half of our refined product is becoming obsolete.

"Second, the demand worldwide for diesel has risen sharply in recent years (EDITORS NOTE: Cars with diesel power plants have been outselling their gasolene counterparts in Europe since 2006).

"The deregulation of the economy and the introduction of the deportee in the early 1990s have conspired to spike the demand past what our plant can manage. This, coupled with the lower yield of diesel (two percentage points less than gas) and the fact that Petrojam can only refine 65 per cent of Jamaica's fuel needs, mean that it is impossible for the price to remain at the levels the market used to enjoy.

"On top of this, Petrojam is responsible for 83 per cent of Jamaica's fuel needs, so the shortfall has to be imported ... at post-refinery prices. This drives up the price of the fuel even more."

Ageing plant

When asked about the quality of diesel fuel delivered to the consumer, Morgan said that this again was due to age of the plant, as it was designed for criteria that were state-of-the-art for 1966. He said that the crude available at that time was far 'sweeter' (had a lower sulphur content) than that which is obtainable now.

"It is my theory that we are now scraping the bottom of the barrel, as it were, in terms of the quality of the oil we are now getting. These contaminants constitute a higher percentage than the crudes of long ago. This plant was also designed around the standard then, which was 5000 ppm (parts per million).

"With today's diesel engines, this is barely acceptable. But plans are afoot to have that figure down to ultra-low emission levels - less than 20 ppm - by 2012."

NOTE: Part 2 of this article will be published next week.

Email: mario.james@gleanerjm.com or columns@gleanerjm.com.