Petroleum

American drivers burn approximately 400 million gallons of gasoline each day. Obviously, the gas in your tank comes from petroleum—a fossil fuel that is extracted from the earth and refined to produce fuels and myriad other products, from asphalt to plastics.

As our supply of traditional oil shrinks, we’re beginning to tap “unconventional” sources of petroleum. These new sources may extend existing supplies, but likely will exact a higher environmental cost than conventional petroleum.

As you know, gasoline pollutes when we burn it in our cars. What most of us don’t consider is that gasoline pollutes even before you put it in your tank. Extracting a barrel of crude oil, refining it into gasoline, and transporting that gasoline to end users is a process that consumes energy and emits pollution and greenhouse gases. A study by Argonne National Lab estimates that every gallon of gasoline you buy already has put five and a half pounds of carbon dioxide into the atmosphere before you use it in your vehicle. Analysts call these emissions “upstream” or “well-to-pump” emissions, and they account for roughly 20 percent of the greenhouse gases emitted from gasoline. (The remaining 80 percent occurs when gasoline is burned in a car engine.)

Insult to Injury

Unfortunately, the drive to extract petroleum from unconventional sources means that upstream emissions may get worse in the future. Some of these new sources are “unconventional” sources, such as tar sands: a mixture of sand, clay and bitumen (a heavy, sticky oil). Unlike conventional crude that is pumped from the ground as a liquid, tar sands are solid and cannot be extracted through traditional oil drilling methods. Instead, tar sands are removed either through strip-mining or by a process that uses steam to heat the tar sands in the ground until the bitumen separates and rises to the surface. Both processes are energy-intensive, as is the refining of bitumen into a version of crude oil that then can be refined into gasoline.

The tar sands extraction process has serious environmental consequences in the local areas where it is conducted, such as northern Canada. But perhaps more serious is the global environmental consequences of shifting to unconventional oil supplies such as tar sands. UC Berkeley researchers recently estimated that tar sands and extra-heavy oil were estimated to have upstream greenhouse gas emissions that were between 1.7 and 2.9 times higher than those of conventional crude oil. Producing oil from other non-traditional sources, such as coal or oil shale, leads to even greater increases in greenhouse emissions.

At the moment, most of the gasoline we consume is made from conventional petroleum. However, some experts project that within 10 years, more than a third of the world’s oil could be derived from unconventional sources like Canada’s tar sands. If this occurs, the upstream impact of a gallon of gasoline will worsen. Sorry—there’s no silver lining in this dark and ominous cloud.


  • Matthew

    Hi, im doing a report at school on how to power a car differently and i would wonder if this is relevent to powering cars on petroleum….