PETROLEUM
and bitumen, and use more complex and expensive methods to produce the products
required. Because heavier crude oils have too much carbon and not enough hydrogen,
these processes generally involve removing carbon from or adding hydrogen to the
molecules, and using fluid catalytic cracking to convert the longer, more complex
molecules in the oil to the shorter, simpler ones in the fuels.
Due to its high energy density, easy transportability and relative abundance, oil has
become the world's most important source of energy since the mid-1950s. Petroleum is
also the raw material for many chemical products, including pharmaceuticals, solvents,
fertilizers, pesticides, and plastics; the 16 per cent not used for energy production is
converted into these other materials. Petroleum is found in porous rock formations in the
upper strata of some areas of the Earth's crust. There is also petroleum in oil sands (tar
sands)
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