So much soot belched from the old power plant here that Mike Zeleny would personally warn the neighbors. “If the wind was blowing in a certain direction,” Mr. Zeleny said, “we’d call Mrs. Robinson down the street and tell her not to put out her laundry.” That coal plant is long gone, replaced by a much larger and cleaner one along the vast Saskatchewan prairie. Sooty shirts and socks are a thing of the past. But as with even the most modern coal plants, its smokestacks still emit enormous amounts of carbon dioxide, the invisible heat-trapping gas that is the main contributor to global warming. So this fall, a gleaming new maze of pipes and tanks — topped with what looks like the Tin Man’s hat — will suck up 90 percent of the carbon dioxide from one of the boilers so it can be shipped […]