Power plant emissions that cause acid rain, water pollution and destruction of the ozone layer may actually be made worse by capturing the CO2 and pumping it deep underground, a new study reported online and in an upcoming International Journal of Greenhouse Gas Control suggests. This increase of other emissions is largely because collecting and burying CO2 — a process called carbon sequestration — requires additional energy, new equipment and new chemical reactions at the plants. And using current technology, meeting all of these requirements releases extra pollutants.
Captured CO2 must be compressed to about 100 times atmospheric pressure (which takes energy), transported to a suitable underground reservoir (which takes energy) and pumped into the ground (which takes energy). A coal-fired power plant that sequesters its CO2 must burn about 30 percent more coal than conventional plants to cover these energy needs. And that extra coal must first be mined (which has environmental effects) and transported to the plant (which takes fuel) — the list goes on and on.
Even with this extra burden, 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.
If the mining, transportation and other supporting technologies become greener in the future, the pollution penalty for carbon sequestration would be reduced, the researchers note.
At the time that IPCC scientists were writing the 2005 report, “everyone was thinking what are the environmental benefits of [carbon capture], not so much the environmental costs,” comments Ken Caldeira, an ecologist at the Carnegie Institution for Science in Stanford, Calif., and another lead author of the IPCC report. “The costs people talked about were mostly economic costs.”
– from Sciencenews