May. 19, 2010 - Issue #761: Public Enemy
The dilemma of the ponds
Tar sands tailings ponds remain an environmental quagmire
Last week a lawyer for Syncrude, Robert White, told provincial court Judge Ken Tjosvold that Syncrude can't be legally responsible for the birds that land in its tailings ponds as preventing all birds from touching the contaminated water is impossible. If Syncrude is guilty in the case of the 1600 ducks that died in its tailings pond in April 2008, White argued, so is every other company with a tailings pond.
"The evidence is unequivocal that you have to have a settling pond," White told Tjosvold. "You have to have unrecovered bitumen. There is going to be (bitumen) froth and if you have a froth, anything that lands on it will be killed. Those are absolute givens."
It's those givens that are becoming the centre of debate at the Syncrude duck trial, as it's come to be known. White's closing arguments reveal an environmental dilemma: to have the tar sands is to have environmentally damaging tailings ponds which currently have never been successfully reclaimed. Even though scientists around the world are trying to find better ways to clean up the water and avoid using as much in the first place, their advances so far have been modest and water, and the ability to reclaim the surrounding environment, will remain a key environmental issue for the tar sands for the foreseeable future.
At the heart of the debate remain the tailings ponds themselves. White's statement paints the tailings picture: the ponds are so big that stopping any and all birds from landing on them may well be impossible. Every day, roughly two billion litres of water—enough to fill 800 Olympic swimming pools—are added to the ponds, which are already over 11.5 trillion litres in volume.
The largest one, located near Mildred Lake just north of Fort McMurray, is big enough to meet the water needs of a town of 70 000 people for 50 years. Except, of course, that no tailings pond is fit for human (or animal) consumption: they're filled with water that's been diverted from the Athabasca River and used to extract bitumen, a viscous, tar-like form of petroleum, from the Athabasca tar sands. As a result, the water is toxic to humans, fish, birds and even bacteria.
Covering an area of more than 130 square kilometres, these tailings ponds are far from scenic, but they're currently the easiest way for oil companies to deal with the toxified water, not to reclaim or de-toxify, but essentially to store the contaminated water.
"In bitumen processing water is a big, big problem," says Greg Dechaine, a researcher at the Centre for Oil Sands Innovation at the University of Alberta.
About 20 percent of the bitumen in the tar sands is close enough to the surface that companies like Syncrude get at it using giant shovels and dump trucks in open pit mines. The remainder is so far underground that it has to be pumped to the surface using steam and suction.
Once the sand is out of the ground, companies use a bitumen-extraction process developed by Karl Clark at the University of Alberta in the first half of the 20th century. Actually, calling it a process might give the wrong impression as essentially, the sand is simply blasted with hot, pressurized water. Dechaine describes it as "like taking a plate and running it under the tap and you just basically blast all the bits and pieces off."
The amount of water required to do this varies based on the origin of the sand. If it comes from an open pit, it takes between two and 4.5 barrels of water to obtain one barrel of bitumen. But if the sand is extracted from deep underground, about one barrel of water total is required.
Once separated from the sand, water and clay, the bitumen goes on to be processed into usable fossil fuels. The water is recycled in this process until it is saturated with hydrocarbons and metals from the sand and cannot be used anymore. After that it goes into one of the ever-growing tailings ponds.
The tailings ponds' water use "is the equivalent of the use of a city the size of Calgary," says David Schindler, a professor of ecology at the University of Alberta and a leading water scientist. "Right now, it's just sitting there indefinitely."
Schindler sees the tar sands as a threat to the long-term health of the Athabasca River. Taking water from the river when it freezes over in the winter lowers oxygen levels in the water, making it more difficult for fish to respire. He has called for a moratorium on the development of new tar sands extraction plants until more research is done into reducing their environmental impact.
Greenpeace activist Mike Hudema is even less optimistic. "We don't think that there is a green solution to the tar sands," he says. "You can reduce some of the tremendous impacts of the tar sands, but even when you look at how much that equates to at the end of the day, it's still too much for us to ethically accept."
The judgement in the Syncrude duck trial is expected to come down in June. Syncrude will likely lose its case and shrug off the penalties, Hudema says, because the company can pay off the resulting $800 000 fine "in a few hours of profits."
While the ponds keep growing, some scientists have dedicated their efforts to discovering some way to clean up the contaminated waters.
Richard Johnson, a biologist at the University of Essex, has discovered a way of using microbes to break down some of the toxic hydrocarbons found in the end-process water—specifically napthenic acids. Johnson treated a naphthenic acid solution with a cocktail of naturally-occurring bacteria, and found that the bacteria will totally metabolize some of the acids into water and carbon dioxide. However, the more complex, branched acid molecules did not break down completely.
Strangely, the acids Johnson's bacteria ate are toxic to the microbes themselves.
"We've found in many of our experiments that the acids are toxic to the bacteria as well," he says. "So, if we add too much of the acid, the bacteria will just all die, and then not eat any of them. So you need to kind of strike the right balance."
Finding that balance might be a bit of a problem. The microbes exhibited symptoms of toxicity at acid concentrations as low as five milligrams per litre, and naphthenic acid concentrations in tailings ponds can be up to 24 times that. Still, Johnson remains optimistic that microbes will be used to clean up tailings ponds eventually, though he concedes it might be decades away.
Another approach to making the tar sands more water-friendly is to use an extraction process that doesn't require water. Environmental engineer Selma Guigard at the University of Alberta has developed one way of doing this.
Guigard's approach involves "supercritical" carbon dioxide—a heated, pressurized solvent that behaves somewhat like a liquid and somewhat like a gas.
Her method mixes supercritical carbon dioxide with tar sand and then depressurizes the slurry, forcing the bitumen to separate from the rest of the mixture. The carbon dioxide can be recycled indefinitely, and the only water involved in the process is that already naturally mixed with the bitumen, sand and clay.
Unfortunately, the technique has yet to be tested at the sort of scale that would let it replace the Clark process in northern Alberta. Guigard has had difficulty raising funds from industry to construct a pilot plant to test the technique.
Murray Gray, the director of the University of Alberta's Centre for Oil Sands Innovation, predicts that Guigard's method won't be used in industry any time soon because carbon dioxide simply doesn't mix well enough with bitumen to be viable.
"Nothing that's been published shows that you can get good dissolution of the bitumen in carbon dioxide," he says. "Unless someone can lick the solubility problem, it won't be used."
Gray's Centre is doing its own research into non-aqueous extraction using solvents like paint thinner. Currently, the Centre is trying to understand the fundamentals of how that might work.
"What we didn't do was run into the lab with a bunch of pots and pans and start playing around with different solvents and additives," says Gray. Instead, the Centre is focused on the basic research required to design a practical non-aqueous extraction process. Gray estimates that their method is six years away from being used by industry.
Guigard thinks any new bitumen extraction process will face an uphill battle with industry.
"There's an infrastructure surrounding the water extraction process," she says. "There's a pretty big challenge in changing the status quo."
With environmental solutions a long way off, the tailings ponds continue to present a serious hazard to wildlife in northern Alberta. The Canadian Association of Petroleum Producers encourages mine operators to use "cannons, scarecrows, decoy predators and radar/laser deterrent systems," but, as the Syncrude trial illustrates, they don't always work.
While Tjosvold deliberates on Syncrude's legal liability, the toxic lakes in northern Alberta will only get bigger. As they continue to grow, environmentalists like Schindler and Hudema are pessimistic about the future of the Athabasca River. Schindler says he sees no new methods on the horizon that could operate at the needed scale.
Hudema says that even if non-aqueous extraction becomes available, its cost will likely prohibit its use.
"This is not a question of the technology not being there," he says, "but simply that these companies don't want to pay to implement it." V
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