Oil extracted from Alberta’s tar sands has gotten a bum rap in climate circles lately. Because it takes more energy to refine petroleum from these sand deposits than from conventional sources of crude oil, the Canadian oil gets labeled as “dirty oil.” A lot of this Canadian oil is delivered to and burned in the United States.

No doubt, oil from the Canadian sand deposits has a bunch of bad attributes. A lot of water is used in the extraction process, acid rain is produced, and virgin boreal forest is destroyed in favor of “reclaimed” acreage of planted saplings. Those impacts alone should drive a decision not to extract oil from tar sands.

By the time it is converted to petroleum and burned as gasoline, a barrel of oil from Canadian oil sands emits 600 kilograms of carbon dioxide (kg CO₂), about 15% above the current U.S. average of 530 kgCO₂. About 440 kg of the CO₂ derives from the gasoline and the remainder from energy used during its extraction and refinement. Thus, when tar sands are the basis of the gasoline, about 73 to 83% of the CO₂ from automobiles stems from the gasoline itself and the rest from the extraction process.

Critics of Canadian oil point out why it takes a lot of energy to extract the oil from oil-sand deposits. Generally, we should avoid a resource where the usable product -- a synthetic crude oil -- is so different from the raw material we find in nature. Conventional oil from the Middle East is a liquid when it first flows to the surface, so less energy is needed to refine it to useable fuel. With oil sands, there is substantial heating to convert the fuel from its solid form, known as bitumen, to synthetic crude oil.

Is the fact that some energy is needed for conversion reason enough to prohibit the use of oil sands?  We regularly convert energy from one form to another, when we find that one form of energy is more useful than another. All of us could burn coal in our home for heat and light, but we often find it easier to use electricity, derived from the combustion of coal and converted to a more useful form of energy.

Transportation now accounts for about a third of the carbon dioxide emissions from all human sources.  Globally, transportation is highly dependent upon oil from the volatile nations of the Middle East.  No wonder we look to the stable politics of Canada as a haven for oil deposits.

Now that we know it’s there, it is pretty likely that all of the Canadian oil sands will someday be extracted -- the real questions are how we do it and how fast. A decision about what is best for the environment should not be based so much on whether the gasoline produces 530 or 600 kilograms of carbon dioxide, but whether and when we choose to drive our cars -- how much gasoline we use at all.

When it comes to climate, we should not point the finger unilaterally at the oil sands.  All oil is in some sense dirty oil. Now is time to wean us from the diet of 20 million barrels of oil used each day in the United States. How and where the oil is harvested adds only a small amount to the carbon dioxide generated by the fuel itself.

The real decision should come from you and me: when we decide if we would be better off living closer to where we work, whether the trip to the grocery store is really necessary, and whether we couldn’t do all our travel in a smaller or more efficient vehicle.  The answer to these questions will be easier when gasoline costs more.  For that, we can simply wait until the supply has diminished, the Middle East has accumulated all our wealth, and our climate is unhealthy. Or we can enact a carbon tax now, the income of which can be used to create alternatives to petroleum and avoid the need to squeeze the last drop from the Canadian oil sands.