“Oil, no pun intended, seeps into just about everything in the economy,” said David Garfield, a managing director at the consultancy AlixPartners. And though petrochemicals usually aren’t burned for fuel, they share in the environmental impact of petroleum when extracted and refined using energy-intensive methods. 
New York Times - Since petroleum replaced whale oil as a main fuel source more than a century ago, chemical companies and refineries have found a startling range of uses for it, from asphalt to vanilla flavoring in ice cream to pills from the drugstore. It has oozed into everyday life, so reducing dependency is a more complicated proposition than some might think.
“It just turns out to be a very abundant product that is easy to manipulate chemically, so you can turn it into many different products,” said Dr. Benny Freeman, past chairman of the American Chemical Society’s polymeric materials division.
Take a typical barrel of oil. About 46 percent of it is refined into gasoline, and another 40 percent or so is turned into jet and fuel oil. Only about 2 percent becomes petrochemicals like polyethylene and benzene for everyday products (with the rest going to other uses).
When oil prices go up, as they have markedly in the past year, companies reassess how they transport items, try to cut down on energy costs, and look for alternatives to petroleum-based materials. For example, some are replacing the hard-to-open plastic clamshell packaging that many consumers find so annoying. But, said Michael Pishko, head of the department of chemical engineering at Texas A & M, there are only a few alternatives to petroleum-based chemicals (one is natural gas as a base for polyethylene). “Beyond that, it becomes very difficult to compete with petroleum, even petroleum at $100 a barrel,” Dr. Pishko said.
Michael Watts, a professor of geography and development studies at the University of California at Berkeley, agreed. “The complexity of these hydrocarbons is sort of remarkable,” he said. Even as a critic of oil dependency, he concedes that petroleum’s versatility is impressive: Not only does the American farm and grocery network rely on cheap fuel for low-cost shipping between the coasts, but food itself is grown using petroleum-based fertilizer. (Oil byproducts for food typically fall under federal regulation, although that doesn’t satisfy critics of petroleum-derived food colorings, for example.)
