KERR: What goes into making a gallon of gas?

By David S. Kerr

Published: June 6, 2008

There is hardly anyone who watched TV as a kid in the 1960s who can’t sing the theme song of the “Beverly Hillbillies.” Don’t act so sophisticated; you know you remember it.  I’ll even help. “Come and listen to a story about a man named Jed, a poor mountaineer, barely kept his family fed, then one day he was shootin’ at some food, and up through the ground came a bubblin’ crude.”

Jedd made his money finding oil.  Crude oil that is, and today, if you have lots of crude oil, whether you own wells here in the U.S., in Venezuela, Saudi Arabia, or the North Sea, you’re doing well.  However, to turn all that crude oil into the petroleum products we use everyday, from gasoline, to diesel oil, and even tar for sealing roads, is no small effort. It’s an amazing process. Often, we talk about the price of a barrel or crude oil, but most of us have no idea of what goes into making it. 

Crude oil, Jedd Clampett’s black gold, is what one chemist called a big pile of gooey hydrocarbons. This means, in layman’s terms, that a barrel of oil, is packed full of energy.  Crude oil, what comes out of the ground, is about 84 percent carbon, 12 percent hydrogen and about 1 to 3 percent sulfur. While crude oil is black and viscous, its quality is by no means uniform and can vary depending on its specific gravity and its sulfur content.  For example, oil that has a low sulfur content is called “sweet.”

On the other hand, if it has a high sulfur content it is considered “sour.” Sour crude, since the sulfur has to be taken out during the distillation process, is more expensive to produce.  Unfortunately only 30 percent of the world’s reserves are sweet.  So, as the price of oil goes up, more and more sour oil is going to the refineries, and that added cost of taking out the sulfur becomes yet another factor pushing up the cost of gallon of gas. But I’m getting ahead of myself.

Oil prices, what you hear quoted on the news, reflect a number of what are called benchmark prices. There is the Brent Crude price which refers primarily to the benchmark for most Northern European oil prices. There is the Amsterdam spot price, the West Texas Intermediate price, and one benchmark, called the OPEC basket. This is the benchmark the OPEC nations use to merge their different products, from Saudi Arabian light crude, to Iran heavy, into one benchmark price. That helps them manage their cartel and control the price. What this all means is that in the business of buying and selling crude, it’s by no means a simple process.

The big challenge, whether the oil is sweet, sour, pumped in Nigeria, West Texas, Indonesia, or Pennsylvania, is in refining it. The oil companies say this represents as much as 10 percent of the total cost of getting it to market. However, refining capacity, because it’s so limited in the United States - we haven’t issued a permit for any new refinery since 1976 - has a significant effect on supply and therefore is a major factor in further pushing up the price of gasoline.

There are 146 refineries in the U.S. The largest is in Baytown, Texas. This plant can handle 562,400 barrels a day. The smallest is a refinery in Nevada that on a good day can handle 2,000 barrels.

Oil refining, particularly for the big refineries in Texas and Louisiana, is industry on a massive scale. These plants cost billions, employ thousands, and run 24 hours a day.  To take crude oil and turn it into finished products begins with what’s called fractional distillation. This process recognizes that various hydrocarbon strands that, depending on the number of carbon atoms, the basic determination of the product they become, conveniently boil off at different temperatures. Gasoline boils off at one temperature, heating oil and kerosene at a bit higher temperature, diesel oil a little hotter still, and finally, at around 320 degrees centigrade, lubricating oil and paraffin. Clearly, it takes a lot of energy to make refined petroleum products.

The fuels are often further refined, using an array of chemical processes, to break apart or combine hydrocarbon molecules as needed, to make the desired products. What most of us probably don’t realize is that out of one barrel of crude, which is 42 gallons, only 19 of them become gasoline. That’s a sobering statistic. That means keeping the nation in gasoline, and keeping us on the road, requires lots of barrels of crude oil. While that’s a distressing statistic to consumers, to oil producers and oil refiners, it is just the way the business, and in this case, the chemistry, works. 

David S. Kerr is an Aquia resident and a former member of the Stafford County School Board. Contact him at info@stafford countysun.com.