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A Coal Plant That Buries Its Greenhouse Gases

The first commercial power plant to use carbon capture and sequestration shows the potential of a crucial technology.
December 10, 2014

Boundary dam, a power plant in Estevan, Saskatchewan, is the first commercial coal-fired plant to capture carbon dioxide from its emissions, compress the gas, and bury it underground. The plant demonstrates that so-called carbon capture and storage (CCS) can work at a large scale—a crucial achievement given that CCS could play a significant role worldwide in reducing the greenhouse-gas emissions that contribute to climate change.

Right now only two other CCS power-plant projects are under construction, both of them in the United States. That’s because CCS carries a hefty price tag: SaskPower invested $1 billion to equip one of the four generators at its Boundary Dam site for carbon capture. What’s more, the process reduces the 160-megawatt plant’s electricity output by about 20 percent, meaning it may cost SaskPower more per kilowatt-hour to run CCS than the 12 cents it gets for selling the electricity.

1. Coal from a nearby strip mine is pulverized for burning.

2. Ductwork (bottom left) carries flue gas to an adjacent carbon capture facility. There, it bubbles through a 52-meter-high column filled with a solution containing chemicals called amines, which absorb 90 percent of the carbon dioxide. The rest vents from the facility.
3. The carbon-rich amine solution (RAC) is piped to a heater that removes CO2; the lean solution (LAC) is piped back to repeat the process.

4. Cooling water travels through the green pipes into a chamber that helps cool carbon dioxide as part of a compression process.
5. The carbon dioxide is turned into a supercritical liquid inside this 15-megawatt compressor. Approximately 3,000 tons of carbon dioxide is captured and compressed every day.

6. A gauge at the CCS plant indicates the flow rate of carbon dioxide.
7. Most of the carbon dioxide travels 65 kilometers to an oilfield (shown here), where it’s injected to help boost production. But some is injected at SaskPower’s site.
8. At the SaskPower site, a wellhead delivers carbon dioxide to its resting place, a saline aquifer 3.4 kilometers underground.

SaskPower makes up for this in large part by selling much of the captured carbon dioxide to the Calgary-based oil producer Cenovus, which uses it to boost output from its maturing oil wells nearby.

CCS should get cheaper over time. The Intergovernmental Panel on Climate Change, the panel of climate scientists convened by the United Nations, projects that technology upgrades and economies of scale should reduce the price of adding CCS to coal plants to just one-third of what SaskPower spent at Boundary Dam. If so, CCS-equipped coal plants could deliver electricity more cheaply than some other low-carbon sources, including offshore wind power and large solar farms.

SaskPower says that with the lessons it’s learned so far, it could now build a similar CCS project for $200 million less, and that it may soon go forward with CCS at two other aging coal generators at Boundary Dam. It also hopes to help other power companies develop expertise in the technology.

Still, coal plants around the world generally have little incentive to follow suit. In SaskPower’s case, Canadian regulations helped force the company’s hand; that fact, plus the availability of a local buyer for carbon dioxide, makes SaskPower’s effort somewhat unusual. What might be needed elsewhere is a way for utilities to pass along CCS costs to customers, just as many do now to pay for renewable energy sources. Another approach would be to tax carbon dioxide emissions, creating an incentive to bury the gas instead.

The technology must also be proven to work over the long term. SaskPower buries some gas in a saline aquifer on its site. To make sure it stays put, the company has installed above-ground gas sensors plus a seismic sensing array to track subsurface movement.

The United Nations climate panel says similar technology must be installed at all 7,000 existing coal power plants worldwide by 2050 to keep warming below 2 °C, a widely cited threshold for avoiding severe climate change. Meanwhile, new coal plants are still being built, especially in China and India. With coal plants expected to provide one-quarter of the world’s energy supply in 2040, SaskPower could help test the feasibility and safety of burying billions of tons of carbon dioxide emissions.

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