​The Worst Oil in the World: The Crude That’s Tarring the Climate
​Oil. Photo: Anan Kaewkhammul


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​The Worst Oil in the World: The Crude That’s Tarring the Climate

Not all oil is created equal: Some kinds produce 80 percent more global warming pollution than others.

Not all oil is created equal. Depending on where it's extracted, refined, and sold, some crude is much more poisonous to the climate. A team of energy researchers has unveiled an ambitious new accounting project that helps to detail oil's true greenhouse gas emissions, and to pinpoint where the worst oil for the climate is being unearthed. So far, the leading offenders are Canada, China, Nigeria, Venezuela—and California.


By now, everyone knows that oil is ​a leading driver of global climate change. Petroleum vies only with coal for the title of largest carbon-emitting culprit. And as the easy-to-get oil vanishes, we're relying on more desperate measures and more advanced—and more energy-intensive—technologies to keep the crude flowing. That can mean disaster for the climate. And it's why researchers with Carnegie's Oil Initiative have, for the first time, created a Climate Oil Index, the first phase of which has just been made public.

"It's going to help a tremendous amount with climate management," Deborah Gordon, study author and director of Carnegie's Energy and Climate Program, said at the index's release. The authors hope that the index will help civic and business leaders better understand the climate impact of the oil they use—and perhaps inspire dirtier operations to clean up their acts.

After conducting an in-depth analysis of 30 different oils around the world, the investigation found that the "emissions differences between oils are far greater than currently acknowledged." The index demonstrates just how astonishingly wide a gap there is between oil extracted and refined from say, ​Tengiz in Kazakhstan and Alberta in Canada. Of the oils analyzed, Tengiz offered the "cleanest," least carbon-intensive petroleum. The Suncor Synthetic H oil pumped out of Canada, meanwhile, produced the most emissions—over 810 kilograms of carbon per barrel, compared with Tengiz's 450 kg.


"There is an over 80 percent difference in total greenhouse gas emissions per barrel of the lowest GHG-emitting… oil and the highest," the paper notes. There are similar discrepancies between China's Bozhong (just over 800 kg of carbon per barrel) and Norway's Ekofisk (460 kg), the second worst and best performers.

So what's making some oil so much more polluting than others? Everything that happens to oil before it even gets to your gas tank. Before it can be burned as fuel or turned into plastic, oil needs to be refined.

Conventional and light oils extracted from a traditional oil well, for example, require relatively little refining before it can be sold and used for fuel or manufacturing. The problem is, conventional oil is getting harder and harder to come by, as the easily discoverable oil has been either depleted or spoken for as ​global demand has skyrocketed. Corporations and governments are now turning to a host of new techniques and technologies to get at unconventional oil sources—which tends to generate more emissions in the process.

Carnegie identified a handful of key oil types—gassy, heavy, watery, and extreme oils—that generate much higher emissions than standard oil.

The most famous example is Canada's tar sands (where some of the world's most climate-tarring oil comes from) which is home to extra heavy bitumen that needs to be refined much more exhaustively than conventional oil before it can be sold, which requires more energy and thus generates more emissions. Tar sands oil is such a carbon nightmare that in 2012, James Hansen, then NASA's top climate scientist, ​said extracting and refining Canada's reserves would be "game over for the climate."


Another oil field singled out for its heavy "synacrude" production is V​enezuela's Hamaca, whose product needs extensive, carbon-costly refining, too.

The more unconventional and more complex the oil is, the harder it is to refine. For an idea of what that refining process looks like, Carnegie has a handy, brain-scrambling graphic:

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As a result of their very heavy crude needing to go through the longest paths outlined above, Canada's tar sands spent years lying dormant. It was just too expensive to extract and refine the stuff, until surging global demand raised prices high enough to make it economical.

More companies are turning to what the report calls "gassy oils," too, often by exploiting hydraulic fracturing, or fracking. These kinds of oil wells are prone to flaring, the practice of releasing bursts of methane, a mega-greenhouse gas, into the atmosphere as a waste product. This happens when wells are poorly regulated or lack the proper equipment, and, of course, significantly ups the oils' emissions quotient. It's why oil from China's Bozhong produces some of the most emissions-heavy in the world—it's rated "high flare" by Carnegie. Nigeria's Obagi oil field also releases tons of emissions in flaring.

The index also lambasts "watery oils and depleted oils" like the stuff collected from California's Midway Sunset oil field. Yes, some of the worst oil for the climate is pumped out of one of America's greenest states. That field, which is 100 years old, needs to have a huge amount steam injected into it before oil can be extracted, which requires natural gas, and "means almost half of Midway Sunset's total greenhouse gas emissions are released before the resource even gets to market."


Lastly, "extreme oils" are oils collected from super energy-intensive operations, like Exxon's Chayvo oil field in Russia, where the well ​runs over 12,300 meters deep—that means it reaches further into the ground than the Burj Khalifa, the world's highest building, is tall. Moving oil through its complex, seven mile-long well system also requires an upfront energy input that means the total emissions generated by the oil production end up a lot higher.

The authors call attention to petroleum coke, or petcoke, which is a byproduct of the oil refining process, is pure carbon, and is often exported or burned for fuel—at immense emissions cost.

"The fate of petcoke going into refineries around the country is a really big question," Gordon said. "If you do something productive with the bottom of the barrel you can reduce emissions quite a bit."

Our desperate rush to squeeze every last drop of oil out of the planet, bankrolled by some of the richest corporations in history, has yielded some ingenious technologies and unprecedented extraction operations. They clearly come with a stark cost to the climate—and they're not going away any time soon, even if Tesla takes over the world. While fuel economy standards in the US and China have helped reduce demand, oil companies aren't about to give up all their immense extractive and refining infrastructure, even if we start transitioning to hybrids or electric cars.

"There's going to be less and less gasoline used, but that doesn't mean oil is going away," Gordon said. "It's going to be used differently."

Thus, the index, which will be expanded and improved with more data, should not only serve as a useful resource for policymakers and oil consumers, and provide crucial input to officials monitoring emissions output. It should serve as a reminder that our addiction to oil is driving us to find new and complex ways to despoil our planet, and that we are often deploying technology in service of exacerbating our problems, not fixing them. And that the age of oil is far from over.

This story is part of The Building Blocks of Everything, a series of science and technology stories on the theme of materials. Check out more ​here.