Alberta’s oil sands have a reputation for being extremely carbon intensive. A report released Tuesday suggests such claims are overblown.

Below are a few things to keep in mind when reading about this study, or any other that compares carbon emissions from different fuel sources.

Tuesday’s analysis comes from the Massachusetts-based IHS Cambridge Energy Research Associates. It concludes that on a “well-to-wheel” basis, oil sands fuel is on average 5 to 15 percent more carbon intensive than regular fuel.

Here’s how that sentence breaks down. “Well-to-wheel” refers to the complete life-cycle of any given fuel.

First you “extract” (taking the oil out of the ground). Then you “refine” (turning the raw resource into products such as gasoline). Finally, you “combust” (using the fuel to power your car). Emissions are produced at each step.

But as the CERA report points out – and oil industry-types like to emphasize – 70 to 80 percent of all life-cycle emissions come from the “combusting” stage.

Basically, as long as your tank is filled with gasoline, you’re producing emissions. And the amount of greenhouse gases released from an exhaust pipe stays constant, the report notes, regardless of where that gasoline came from.

"On this basis," a press release reads, "[CERA] found that GHG emissions from oil sands product do not differ much from other sources of US crude imports, including crudes from Nigeria, Venezuela and some produced domestically."

Here’s where it gets more complicated. Emissions from different types of fuel sources can vary wildly in the “extracting” and “refining” processes.

Take Alberta’s oil sands. Companies either claw a viscous substance called bitumen from massive open-pit mines, or melt it from underground formations with steam injections. The bitumen must then be heated at high temperatures and diluted with chemicals before it’s even ready to be sent through a pipeline.

Conventional oil, in contrast, is pumped relatively easily from the ground, and does not require nearly as much refining.

So on a “well-to-tank” basis – only including emissions from “extracting” and “refining”, not those from “combusting” – oil sands fuel creates 82 percent more greenhouse gases than regular fuel, the U.S. Environmental Protection Agency estimates.

Most "well-to-wheel" fuel emissions come from end users – people driving SUVs, for instance. But the remaining 20-30 percent is still significant in the eyes of many environmentalists.

“Cleaner forms of extraction and refining of fossil fuels offer huge potential for [greenhouse gas] reductions,” reads a recent Friends of the Earth Europe report.

Geoff Dembicki reports for the Tyee.