FEEDING OUR OIL HABIT: HARD CHOICES
February 10, 2013 § 9 Comments
The Keystone XL pipeline hangs in the balance on the President’s desk. Opposition to it is the cause du jour of the Sierra Club and certain celebrities. The Sundance Kid has an op ed in a recent Huff Post railing against the “dirty oil” from Canada. So, how dirty is Canadian oil and what are the alternatives? I think we all recognize the reality that displacement of oil based fuel is going to be incremental. So we are going to have to make choices regarding the sources of our oil.
The top four sources for our foreign oil are Canada, Venezuela, Saudi Arabia and Mexico. Most of the oil from all but Saudi Arabia is classified as heavy oil. Even Saudi oil is starting to get heavier. The term heavy is used for the fact that the oil has a greater proportion of large molecules. As the molecule gets larger, the relative proportion of carbon by weight compared to hydrogen is higher. When such oil is refined, the long chains are broken down thermally and hydrogen added. This process is known as hydrothermal cracking. For particularly heavy oil a carbonaceous residue is left known as petroleum coke.
The charge of “dirty oil” leveled against Canadian oil is based primarily upon the fact that the petroleum coke, if utilized, releases carbon dioxide. Clearly a processed light oil such as the shale oil from the Bakken or Eagle Ford has very little of this residue and so is clean in comparison. But petroleum coke is in fact quite comparable to coal. The energy content is generally a good deal higher than most grades of coal and the ash content is much lower. But it usually is worse on sulfur content. For workhorse applications such as cement kilns that is of little consequence because of the presence of agents that capture the sulfur. Petroleum coke also has significant quantities of heavy metals nickel and vanadium. This almost all ends up in the ash in a form that is essentially not leachable by water. Nevertheless, this too is another reason for the “dirty” appellation.
In the event of a spill heavy oil biodegrades more slowly. This is in part because oil eating bacteria prefer the smaller morsels of the light constituents. On the other hand it will not leach into the soil as readily because of the viscosity. This notwithstanding, the originally proposed route for the Keystone XL was ill conceived. It went through a portion of Nebraska where the sediment was very porous, and this overlaid the Ogallala, the most important aquifer of the region. The proposed new route is longer (see red portion on map), but avoids the potential for aquifer contamination.
A little discussed fact is that the pipeline will also carry some of the light oil from the Bakken shale oil fields in North Dakota and possibly Montana. This important new source of light oil is currently being transported by truck and rail, increasingly the latter. Both of these forms, especially trucks in the northern climates, would appear to be more spill prone than pipelines. Besides, absent a pipeline the Bakken oil will likely be limited in production, which is not good news for domestic output.
Consider the scenario of the Keystone XL not being permitted. The Gulf Coast refineries have expensive equipment known as cokers, specially designed to handle heavy oil. If Canadian oil is curtailed they will source heavy oil elsewhere. The best bet is Venezuela, already a source. The carbon loading of this oil is very similar to that from Canada. Furthermore, the nickel and vanadium concentrations are three to four times greater. Trading Canadian partnership for dependency on a country with leadership unfriendly to US interests sure sounds addled.
Finally, consider the question: can Canadian crude be cleaned up before it comes to us? The answer is yes. The simplest way to accomplish this is to remove much of the excess carbon prior to shipping using a technique known as de-asphalting. When propane, hexane or a combination are added to heavy oil, they pick up the lighter component of the crude and the carbon heavy asphaltene drops out as a solid. The extracting liquid can be regenerated for re-use and the so called de-asphalted oil (DAO) can be sent down to us. A bonus: much of the sulfur and most of the heavy metals preferentially segregate to the asphaltene, so the DAO is lower in these elements as well.
Our refiners currently get Canadian crude at a heavy discount. The DAO will likely command a better price. The cokers will be underutilized because the oil is cleaner. But the country will be the better for it.