CleanO2, a Canadian company, is selling a line of soap that cleans people while it also helps clean the climate of carbon dioxide. The Calgary-based “cleantech” company's small-scale carbon capture device—known as CarbinX—captures carbon dioxide from building heating systems and transforms the greenhouse gas into pearl ash, which is then used in CleanO2 soap bars. Each CarbinX device currently reduces the amount of carbon dioxide in the atmosphere by 6 to 8 tons annually, according to...