Emitting CO2 would need to cost at least $30 per metric ton via a carbon tax or a cap and trade market for any of the various carbon capture and sequestration technologies to be economically competitive, according to the report. At that price, coal, natural gas, nuclear and renewable electricity sources like wind become roughly cost-competitive, Moniz says. "There is not going to be one silver bullet," he adds. "And without much improved energy efficiency, we have no chance of meeting targets like doubling or less than doubling preindustrial levels of CO2 in the atmosphere," as many scientists have urged as a goal to prevent dangerous climate change.
Ultimately, it is such efforts to combat climate change that drive sequestration needs, and a 2006 M.I.T. poll of 1,200 Americans indicates that they are willing to pay an average of $21 a month for solutions to this global problem. The conundrum is that there is nothing to pay for as of yet when it comes to coal. No "clean coal" technology has been demonstrated with carbon capture and storage and no large-scale sequestration projects have been undertaken. It also remains unclear where and exactly how much storage capacity the U.S. has. "Pore volume that you can use to hold CO2 is a new natural resource," Friedmann says of the underground reserves that might be suitable to contain liquid carbon dioxide. "What is the capacity? What does it look like? How fast can you inject?"
In short, the report finds that coal will remain the electricity-generation king and geologic sequestration is the solution best suited to minimize the attendant carbon dioxide pollution. This will require building a liquid CO2 infrastructure comparable to the national highway system as well as assessing which coal-burning technologies work best with which carbon capture technologies. In other words, the way such carbon capture and sequestration will work remains as hazy as the smog coal-fired power plants produce but it needs to become clear quickly if the world plans to continue burning such fossil sunlight. "How hard and how far can we push capacity in a safe, virtually riskless way?" Moniz asks. "There remains a scientific consensus on viability. Implementation is a different issue."