Saskatchewan has been a coal-powered province for years, its Boundary Dam power plant burning the most polluting forms of lignite since 1959. But thanks to a modern retrofit, Boundary Dam now serves as the demarcation line between dirty and clean Canadian coal power.
"Natural gas prices rise and fall unpredictably, while coal is abundant and affordable in Saskatchewan," reads Saskpower's website. "Government regulations and the need to reduce greenhouse gas emissions around the world means we need to find a way to keep producing affordable power, but in a way that reduces our impact on the environment."
The Boundary Dam has been in operation since 1959 when its first two 62 MW boilers were installed. Two more 139 MW boilers were brought online in 1970, a third 139 MW unit joined in 1973, and a 273 MW unit powered up in 1978; bringing the total to 6 boilers and 752 MW of total capacity. The plant has traditionally utilised locally sourced coal for its fuel, including what's known as "brown coal," a highly polluting form of lignite considered one of the dirtiest forms of coal power. Even worse the Boundary Dam plant would simply port any excess CO2 generated by the energy conversion process directly into the atmosphere.
But beginning October 22nd of this year, that greenhouse gas stopped being dumped into the air and started being pumped deep underground. The technique, known as the aquastore project, involves dissolving the gaseous CO2 into a nearby saltwater aquifer, thereby sequestering up to 1 million tonnes of CO2 annually—that's roughly 90 per cent of what the power plant produces and the equivalent of taking quarter of a million cars off Canadian roads.
Boundary Dam is the world's first Post-Combustion Coal-Fired CCS, which required a 871 million retrofit to unit 3. The carbon capture process will also reduce unit 3's capacity from 139 MW down to 110 MW.
As Scientific American explains:
Boundary Dam also burns brown coal, the most polluting form of the most polluting fossil fuel. Saskatchewan has an estimated 300-year supply of the dirty fuel to burn at present rates of consumption. The unit uses amines—a nitrogen-based molecule that can bond with CO2—to capture a projected 1 million metric tonnes of the leading greenhouse gas each year. The amine captures the CO2 and then when further heated releases it again, meaning it takes away some of the plant's power to take away the plant's CO2. The captured CO2, compressed and liquefied, will then travel 66 kilometres via pipeline to the nearby Weyburn oil fields and join the CO2 captured at a plant that turns brown coal into a gas in North Dakota. At Weyburn, the CO2 will be used to scour more oil out of the ground. Of course, the eventual burning of this oil will also release CO2 into the atmosphere.
It's not a perfect solution—a perfect solution would be the global implementation of pebble bed or thorium reactor technology—but it marks a huge step forward in the establishment of a low-carbon economy. The plant is the 13th facility worldwide to implement capture and store technologies. [SaskPower via Cleantechnica - SciAm - Wiki - MIT]