Fossil fuels

Our modern society is based on “fossil fuels,” which may sound to you like we’re burning dinosaur bones for heat. We aren’t, but we are burning the remains of plants and animals that lived millions of years ago, releasing the solar energy the plants captured through photosynthesis and the animals captured by eating the plants.

A coal bed starts out (we think–very few people have the patience to directly observe a process that takes millions of years) as a silted-over peat bog. As the layer of sediment over the bog increases, it forces water out of the peat. The peat becomes richer in carbon and deficient in oxygen, until eventually hydrogen stops combining with oxygen to form water and instead starts combining with carbon to form hydrocarbons. Spongy, fibrous peat becomes hard, brittle coal: vegetable matter turns into rock.

Similarly, petroleum (Latin for “rock oil”) starts out as layers of marine plankton–microscopic plants and animals–at the bottom of the sea. Sediments build up over these layers, and as in coal, the pressure and heat force out water and oxygen, leading to the formation of a variety of hydrocarbons, from tar to gas.

Humans used coal as a fuel as early as 1100 B.C. in China. Petroleum has also been used for millenia, but not as a fuel. Though usually found deep underground, in some places it seeps to the surface, which enabled our ancestors to use it to caulk boats, to mend roads, as a medicine and liniment, in torches and lamps, and, people being what they are, as an incendiary weapon of war.

The modern age of petroleum began in the 1850s, when overhunting of whales caused the price of the whale oil used in lamps to skyrocket. Starting in Romania, people turned to kerosene, refined from petroleum collected from surface seeps. It quickly became the illuminant of choice (to the relief of whales), which made petroleum valuable, which led to the first oil well, completed on August 27, 1859, in Titusville, Pennsylvania.

All those first oil-drillers wanted was kerosene: they burned off “useless by-products” like gasoline. But then along came the internal combustion engine, and Henry Ford. Today, gasoline accounts for 30 percent of all oil use.

The fact you can get both kerosene and gasoline out of petroleum is what makes it so valuable. Crude oil is made up of many different hydrocarbons, and through the skillful use of heat, technology and chemistry, you can convert any hydrocarbon into any other.

The basic method of separating the various hydrocarbons is to pump hot crude oil into the bottom of a tall steel tower. The lighter (and most valuable) compounds, those with the smallest molecules and the lowest ratio of carbon to hydrogen, vaporize and rise to the top of the tower, where they condense and drop back down to be vaporized again. Since the different compounds condense at different heights, you can draw off what you want: gasoline from the top, kerosene from the middle, and fuel oil from the bottom.

Further refining techniques involving vacuum, heat and catalysts, collectively called “cracking,” can break the big molecules of the less valuable hydrocarbons into small, more valuable molecules: valuable not only as fuel, but as raw material for plastics, synthetic fibers, paints, fertilizers, insecticides, soaps, synthetic rubber and more. Without petroleum, modern industry couldn’t function–more’s the pity, because the use of fossil fuels carries a pretty high cost, starting with the degradation of land during the creation and operation of coal mines and oil fields.

But that’s small potatoes compared to the pollution caused by actually burning the stuff. Coal smoke is an unpleasant pollutant in its own right–the source of London’s infamous 19th-century pea-soup fogs–and the sulfur compounds in coal are the direct cause of acid rain. Burning petroleum, particularly in automobiles, contributes to low-level ozone pollution: smog. Then there are oil spills, from minor losses from truck and car accidents to the Exxon Valdez and oil-well blowouts in the Gulf of Mexico. And finally, there’s the concern about global warming due to the heat-trapping effect of the carbon dioxide produced by burning fossil fuels.

These concerns have sparked research into cleaner ways of using fossil fuels (and ways to avoid using them at all), but don’t dump your oil company shares just yet.

We’re addicted to the stuff, and it’s going to be a hard habit to break.

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