This should be obvious, but of course you never hear it mentioned in stories about carbon capture and sequestration (CCS): capturing and sequestering carbon requires lots of energy; thus, plants that do it have to burn more coal to create that extra energy; thus, the other pollutants created by mixing, transporting, and burning coal will increase if CCS is widespread.

It follows just based on logic, but if you prefer peer-reviewed scientific studies, here’s one for you:

Even with this extra burden [of having to generate more power], a CO2-burying plant emits between 71 and 78 percent less CO2 than a normal coal-fired plant for each unit of usable electricity produced, Koornneef and his colleagues report. But when the researchers factored in all the "cradle to grave" pollution of a CO2-burying plant, emissions of acid rain-causing gases like nitrogen oxides and sulfur oxides were up to 40 percent greater than the total cradle-to-grave emissions of a modern plant that doesn’t capture its CO2.

Doesn’t sound very "clean" to me …